Sciencemadness Discussion Board

toluene --> benzaldehyde

 Pages:  1  ..  4    6  

CycloKnight - 15-4-2013 at 06:29

Sometime this week I'll be revisiting the cinnamon oil to benzaldehyde method utilizing insitu steam distillation, same method I used before with good results. I'll be taking a few photos of the new run, but I'm not sure if the mods want me posting pictures of a technique that's already been documented in this thread (server space, and all that). I don't mind posting pics of the new experimental run if that's okay?

I'm setting up the equipment today, so will be starting soon. Last time I managed somewhere around 80% conversion to benzaldehyde (mass I think, rather than molar conversion) from cinnamaldehyde, so it'll be interesting to see how I get on this time around. I'm using a different cinnamon bark oil supplier this time, but again I'll be distilling the cinnamaldehyde from the cinnamon oil as I did before. I'll be processing one single kg bottle of cinnamon oil into benzaldehyde. The final product will be double vacuum distilled and stabilized with a dash of hydroquinone for storage.

Bot0nist - 15-4-2013 at 09:10

while im not a mod, I feel a "peach syle" pictorial would be a welcome addition to this lengthy thread. Perhaps even an artical for prepublication. It seems that "*** to benzaldehyde" questions are popular with newbies around here. Can't think of why, though... ;)

CycloKnight - 15-4-2013 at 09:58

Not sure what about a "peach style", but I can do a CycloKnight style retro-aldol follow up to my earlier pictorial(s) some years back.

http://www.sciencemadness.org/talk/viewthread.php?tid=2223&a...

Whenever I revisit old teks, since I already know what works, in the interest of improvement I sometimes opt to change one variable to see what (if anything) works better. Its already been recommended that I could try raising the pH higher, so I can give that a go and see if the benzaldehyde conversion is higher.
If anyone has any suggestions as to what might improve this method (quoted below), then this is the time to let me know and I'll give it a whirl.

To begin with, I'll be using the old method I posted in page 6 of this thread back in 2006.

Quote:

I’ve significantly improved the original batch method I posted last year, what follows is my latest method.

This approach uses the same setup as the last steam distillation variation graphically depicted in in this thread.

Basically, the items used were:
hot plate, pressure cooker steam generator & associated tubing, etc
3L 3-neck RBF & mantle
vigreux column, right angle bend & still head
condenser
Vacuum pump & glassware for purfying the final product & recycling unreacted cinnamaldehyde.

chemicals: 2 litres tap water, lecithin, cinnamon oil, NaOH

Essentially, a large reaction vessel and a means of steam & vacuum distilling are all the equipment really required.


Begin by setting up all equipment, add 2 L water & ~1.5g lecithin.
The first variation is to use OTC sodium hydroxide instead of sodium carbonate, simply add the alkali to adjust the pH within the range of 12-13, only small amounts are required.

The second variation is to slowly drip in the cinnamon oil during the course of the reaction, the benzaldehyde being steam distilled as it forms. Begin the addition once the pH adjusted solution has heated to boling temperature and the steam is passing though the solution.

The third variation is to stop the cinnamon oil addition after 5 min, then check the distillate. If benzaldehyde is clearly distilling over, then continue with the addition.
A crude test is to simply taste the steam distillate as it drips into the receiving vessel, if it burns your tongue off, then you're doing well. If it tastes sweet, then significant quantities of cinnamon are being carried over. Should this not change after a short while, then double check the pH !

Provided that the pH is correct and the cinnamaldehyde content is high (70%+) then benzaldehyde laden distillate should start collecting almost immediately after the addition has begun.
However, if it is not, wait for the benzadehyde to start collecting, THEN continue with the addition. This prevents unnecessary amounts of cinnamaldehyde being steam distilled at the start of the process, which is a serious problem with the old batch mode reaction.

Note that by slowly dripping the cinnamon oil instead of adding it all at once to the reaction mix, single run conversion is increased by 20-30%.

Ensure the rate of cinnamon oil drip rate is approximately equivalent to the quantity of oil being steam distilled, thus maintaining high dilution in the reaction mixture.

After 300 to 500 ml of cinnamon oil had been added, the drip rate is stopped and the steam distillation continued until all the aldehyde has been steam distilled from the reaction mix. If using less than 2L of water, then adjust proportionally to maintain the same dilution. At this point, dump the mix and replace with clean pH adusted water with at least ~1.5g lecithin.
This step removes tar and other junk that slows down the reaction and reduces benzaldehyde production. Significantly reduced tar formation will also result from periodically carrying out this step (very imporant if high yields are desired).
Also note that with this method, the pH tends to slowly drop over time during the course of the steam distillation, so check the pH every couple hours, and top up with NaOH if and when required. Its preferable to simply add small amounts concentrated NaOH solution when topping up, using a dropper makes the alkali addition much simpler since NaOH pellets will rapidly collect moisture and stick to the sides of the reaction vessel.

Efficiency is further improved if the steam distillate (after oil separation) is also extracted with DCM, though this isn't absolutely necessary.

Once the the product oil is pooled, vacuum distillation will remove the benzaldehyde - no need to vacuum distill the recycle cinnamon aldehyde, just drip it into the steam distillation vessel, just as with the cinnamon oil feed. Expect the quantity of unreacted cinnamon aldehyde to be circa 25%, but if the reaction mix was kept clean during the process then it may be considerably less. The benzaldehyde distillate is clear, & much purer than the original solvent extraction method that doesn't employ the steam distillation. Give the batch solvent extraction a rest folks, use the steam distillation variation if producing benzaldehyde from cinnamon oil!
Far, far less work.

Using the above approach, overall molar conversion to benzdehyde is at least 80%.

I’ve managed higher conversion efficiencies (~90%), but the reaction efficiency is subject to variation according to varying reaction conditions, i.e. feed rate, reaction mix volume (i.e. dilution), and the quantity of cinnamon oil fed to the reaction mix before changing the solution. >80% seems to be a realistic overall figure.

Also...
Remember to keep the reaction mix free of tar & cinnamon oil impurities as much as possible to give consistent high yields.

If dripping the aldehyde into the mixture isn't practical for any reason, you can periodically add the cinnamon oil in small batches, say 20-50 ml at a time to give good conversion, but expect a little more cinnamonaldehyde to distill over.

questions - 15-4-2013 at 22:42

AWSOME cyclonight :)

What I recomend is to drip say 200ml of cinamon oil into the boiling solution of water with NaOH and steam being blow through it as you did earlier, but this time, make the ph of around 13.5 to 14 and maybe you mght get pure benzaldehyde out the other side. I'm certain you'll loose some product in the process but if you can get say a quick, 60ml to 100ml of pure benzaldehyde out of say 200ml of cinamon oil without having to do a vacuum disstilation, than to me that process is better than any because it would be a quick and easier way of getting a quick small amount of benzaldehyde when we need it. I'm happy to loose say 140 ml of cinnamon oil if I know I'll get 60ml of pure benzaldehyde from it in a simple, quick process that doesnt require as much effort, time, equipment and money. :)

GO FOR IT CYCLONIGHT !!!!!!!!

I'm your biggest fan :)

CycloKnight - 16-4-2013 at 08:52

No problem, any and all input appreciated. :)
I plan to first run through the 1 kg of oil using the previous tek just to see how much benzaldehyde it will yield from 1 litre of oil, but I'll do a surplus run (200 ml or so) with extra oil I have and I'll report back the single pass conversion efficiency at the higher pH.

Well anyhow, we're rolling now. Benzaldehyde is flowing nicely, got around 70 ml so far and its only been a few hours since I fired it all up. Lots of pictures taken, will post the images and write up later in the week after this little project is completed.

questions - 16-4-2013 at 18:27

You rock Cycloknight :)

[Edited on 17-4-2013 by questions]

CycloKnight - 17-4-2013 at 06:23

General setup:


Between the free oil in the steam distillate and solvent extractions, there's about 400 ml so far.
Separating steam distilled oil from condensate:


[Edited on 17-4-2013 by CycloKnight]

CycloKnight - 17-4-2013 at 06:33

Volumetric flask making itself useful


As each litre of condensate comes off, the residual oil at the bottom is drawn off and kept separate, and then the condensate is extracted with two 30 ml portions of dichloromethane. The pooled DCM extracts are kept together, and later the DCM will be reclaimed and the aldehyde residue vacuum distilled.

CycloKnight - 17-4-2013 at 06:41

1 kg cinnamon oil feedstock


Either later this evening (London time) or tomorrow the full kilo of cinnamon oil will have gone through the reaction mix, so then after vac distilling and recycling unreacted cinnamaldehyde I should have the final tally.

questions - 17-4-2013 at 07:41

THESE PICS ARE AMAZING !!!!!

CycloKnight - 19-4-2013 at 15:47

Okay finally have some results now. I'll post the pics in a few days.

No sooner had I set up all the equipment and began the vac distillation of the cinnamon oil, the mag stirrer failed on the stirrer mantle. This has slowed down things somewhat, and I won't be able to reprocess the recycled (unreacted) cinnamaldehyde since I've run out of time. The cinnamon oil was used as is, without vac distilling.

From 1000 g of cinnamon oil, slowly dripped into the pH 12.5 solution whilst steam distilled over 22 hours over 3 days, yielded 560 g of free oil (separated from steam condensate using a separating funnel), and nearly a litre of dichloromethane extracts (2*30ml DCM used per litre condensate).

The DCM extracts were distilled to recover the DCM, yielding about 150 ml of oil remaining (estimated, forgot to weigh).

That oil from the DCM extracts, combined with the free oil, was then vacuum distilled. This proved impossible without magnetic stirring, so had to use an oil bath. The bumping was very severe, even with the vigreux column it was impossible to distill of the benzaldehyde without the aldhyde bumping into the receiver. With mag stirring, it was fine.
Bath temperature was 129 deg C, vacuum was shown as 65 mbar (absolute pressure, but gauge probably isn't that accurate) and benzaldehyde came over at around 105 deg C.

Total benzaldehyde collected = 568 g.
Total residue remaining = 154 g (to be recycled later in next retro-aldol reaction).

Assuming residue is cinnamaldehyde, then that equates to 79% benzaldehyde, and 21% cinnamaldehyde.

Cinnamaldehyde ~ 132.16 amu
Benzaldehyde ~ 106.12 amu
1000 g cinnamon oil (assuming 100% cinnamaldehyde) is 7.56 mol.

Therefore 100% efficiency equates to 7.56 mol benzaldehyde, which is 803 g.

Total single pass benzaldehyde is 568 g, so single pass molar efficiency was 70.7 %. If the starting cinnamon oil wasn't 100% cinnamaldehyde, then the true figure will be higher.

This doesn't take the unreacted cinnamaldehyde into account, so if/when that's recycled the overall conversion will be somewhat increased.
If the unreacted low volatile oil is cinnamaldehyde, then reprocessing should yield
154 g * (0.722) = recoverable oil of which 79% will be benzaldehyde, 87.8 g.
This combined with original yield of 568 g, would then be 655 g, increasing the overall molar efficiency to 81.6 %.

The reaction flask solution was changed each morning, and not changed nor pH adjusted for the entire day. pH was adjusted by adding a round teaspoon of NaOH. Also, two lecithin pills were dropped in.
On the first day I experimented a bit, and added the cinnamon oil in 20 cc doses, but I stopped as this was reducing efficiency (and more tar too) and causing too much cinnamaldehyde to distill over. Maximum efficiency is attained by using a very slow drip rate. I dripped in about 40 ml or so per hour.
About 33 ml of free oil was deposited for each litre of steam condensate. Cinnamon oil drip rate was adjusted to match.

About 6 g of benzaldehyde will dissolve in 1 litre of pure water, and there are always oil droplets floating in solution, hence the reason for the DCM extractions. Towards the end I found that a single 30 ml DCM extraction gets most of the oil out, so two DCM extractions is probably a bit excessive.

It might be handy to know the vapour pressures at 100 deg C.
Benzaldehyde ~ 8 kPa
Cinnamaldehyde ~ 0.6 kPa
Water ~ 101.3 kPa

Took me a while to find the aldehyde values at 100 C, so thought would include them here. These can be used along with each oil concentration in the boiling solution (if known) to calculate the theoretical distribution in the steam condensate (assuming perfect mixing).

[Edited on 20-4-2013 by CycloKnight]

questions - 19-4-2013 at 19:14

AMZING !!!!!!!!!!

:)

Lets cook up some benzaldehyde..

CycloKnight - 27-4-2013 at 13:35

Photo update to my last post.

Chemicals needed:
1 kg cinnamon oil
10g NaOH
10g lecithin

Equipment needed:
Pressure cooker
Hob (1500W)
Heating mantle (or oil bath)
Glassware (3L RBF, vigreux column, stillhead, condenser, separating funnel(s), stoppers, fittings & glass tube for steam injection to corrosive cinnamaldehyde/benzaldehyde mixture)
Aquarium tubing
Aquarium water pump (for cooling condenser)
Receiving vessel(s)

Vacuum pump will be required for final vac distillation, though in a pinch, steam distillation could be used instead (with neutral pH solution instead of 12.5 pH).

Disused kitchen corner


Get the gear out


General setup

Chemicals, from left to right, lecithin, cinnamon oil and sodium hydroxide.


There's virtually no pressure, so any tubing fitting will do.

The aquarium tubing is run from the pressure cooker to a straight glass tube through a stopper in the 3L round bottom flask. Simples.

Cinnamon oil. The more the merrier, but for this experiment I've used 1 kg.




The pH is set once per day, to around 12.5 (this required 1 rounded teaspoon of NaOH granules), and then checked every few hours with the pH paper skewer.


I find that the pH remained fine without topping up until emptying and replacing the solution the following day. 2 lecithin capsules were also added.

Ready to rock'n roll.


Go slowly, about one drop of cinnamon oil every few seconds is a good start.
16 drops per ml, aim for around 40ml addition per hour.

The purpose of the heating mantle heating the 3L RBF is to keep it hot enough that it won't condense steam from the pressure cooker and a little extra heat is needed to keep condensate from the insides and vigreux column reflux from filling the RBF up with water. A medium heat setting is all that's needed.

Going good.


Extracting each litre of condensate with dichloromethane as the condensate is produced.


Here we're producing about a litre of condensate per hour. There's about 33 ml of free oil sitting at the bottom of each litre that comes off, and there will be about 6 ml benzaldehyde dissolved (DCM will remove it).


First tap off the free oil:


Then do at least 1 x 30ml DCM extraction to get the oil droplets and dissolved oil out, before you throw this down the sink (I did 2 x 30 ml extractions, but 1 is probably enough).




I occasionally used a large conical flask to store the condensate litres when it wasn't convenient to extract them right away. I would just fill the large 3L conical flask, and then do 3 x 1L extractions in quick succession.


1000g of cinnamon oil and 3 days later I have 560 g steam distilled oil (free oil) and about a litre of dichloromethane extracts.




Time to distill off the dichloromethane from the extracts, and then vacuum distill the residue and the condensate oil.
This oil (from DCM extractions combined with free oil) was later determined to be 79% benzaldehyde, with the remainder comprised mostly of unreacted cinnamaldehyde.

Stirrer mantle broke shortly after beginning this project, so had to make do with an oil bath.


Vac pump


Benzaldehyde




More refractive benzaldehyde porn...


Nearly enough to fill a 750 cc bottle, 568 g.




Leftover cinnamaldehyde mixture from vac distillation


Total product from 1 kg of cinnamon oil, 568 g benzaldehyde and 154 g of cinnamaldehyde residue still to be recycled in the next lot.



[Edited on 28-4-2013 by CycloKnight]

madcedar - 28-4-2013 at 02:06

CycloKnight

Thank you for going to the trouble to re-visit this procedure. Many people will benefit from your post. Love the lab bench.

Kind Regards

questions - 28-4-2013 at 04:53

Yeah, true. I must agree with Madcedar, it was a good journey this whole procedure and thankyou so much mate for taking us through it :)


CycloKnight - 28-4-2013 at 14:08

No worries chaps, this retro-aldol variation is actually one of my favourite reactions so it's all good fun. With the smell of cherries propagating the house, sometimes it does seem more like cooking that chemistry...

...except when the following morning you check your product beaker (that you forgot to rinse), only to find your exotic sauce cuisine oxidised to benzoic acid crystals.

Having fun in the kitchen it may be, baking brownies it isn't.
As a wise person once said "You ain't in Kansas anymore, Dorothy.".

One last point regarding the drip rate.
I mentioned before to try to balance drip rate with visible oil in the steam condensate, just remember to add an extra 20% to the drip rate (assuming 1 litre per hour steam condensate) to account for dissolved benzaldehyde in the steam condensate (~6 ml litre).
No point adding more oil if it won't steam distill, what doesn't steam distill will inevitably turn to tar in the flask, so overdoing it will reduce the % yield of benzaldehyde.

CycloKnight - 28-4-2013 at 14:50

Here are a couple short video I made during the run, no sound though.
Steam distillation
http://www.youtube.com/watch?v=0zdW0CunIyQ

Steam condensate rate
http://www.youtube.com/watch?v=stEECSuoUPg

Davyrocket - 15-5-2013 at 15:25

omg jfc
5 hours later reading this thread and a bottle of johnny walkers done!...

and still no futher forwared ....

i am not looking for spoon feeding however if i could only have 1 mouthfull of spoon feed info on the best direction to benzaldehyde from my location in \\uk that would be most appreceated....

i cant go this diriction i cant go that direction..all because of my ffff location and chem avalability..
if some kind chemist out there from the uk
could even pm me on a good route for me to go
or post....as there probebly more than just me in the same
posistion...

i would be much greatfull to them

and i prommis not to post anymore crap untill i come up
with somthing good

thx davyrocket


ps nico my boy feel fre to tell me to piss of and move post
i would if it where me:D

Bot0nist - 15-5-2013 at 15:38

You cant get toluene and oxidants in the UK? You have the internet, obviously, so cant you just order some cinnamon oil or even bulk cinnamon, or almond attracts. If you cant source these basic precursors, then how do you plan to get to your assumed target molecule. Probably easier to walk the streets looking for what you want... Sorry if I have assumed to much, but your starting to sound like a "lazy cook." No offence intended, just my perception. Don't let the whiskey make you post sloppy or flame either. we are (mostly) all rational adults here.

Davyrocket - 15-5-2013 at 15:59

Bot0nist i am far from beeing a lazy cook

i am actualy planning to start a science course this september
even at my age of 32, however you are probably right about the whisky...

if some one could even post me or pm a patient
that would be suitable for uk chems.....

i would not stop reading and studying until
i masterd it...or untill my eyes poped out my sockets

its just like my head is going to explode with it

but look i dont want to ff up a perfectly good post with my retorical bs....

i was thinking with a benzelalcholo starter

and sorry for being a assssss

Bot0nist

its maybee the irish breaking out of me
sry for spelling


thx the rocket

questions - 18-5-2013 at 22:56

All the same, inorder to make benzaldehyde, you still need all the right equipment, glassware ect, its not something anyone can do without all the right stuff :(

manimal - 23-5-2013 at 23:06

Quote: Originally posted by madcedar  
CycloKnight

Thank you for going to the trouble to re-visit this procedure. Many people will benefit from your post. Love the lab bench.

Kind Regards


It's good to see you.

vmelkon - 27-5-2013 at 20:02

Has anyone tried with commercial grade toluene?
Someone mentioned in this thread that they contain thiotoluenes and this interferes with the reaction.
My source of MnO2 would be from batteries.
I do have some KMnO4, if it can be used directly in this reaction.

I was thinking of the reaction between toluene + MnO2 + H2SO4 as mentioned in the first post, not the cinnamaldehyde --> benzaldehyde.

What is a thiotoluene? Is it something like this?
http://www.chemicalbook.com/ProductChemicalPropertiesCB15115...

questions - 28-5-2013 at 23:25

Quote: Originally posted by vmelkon  
Has anyone tried with commercial grade toluene?
Someone mentioned in this thread that they contain thiotoluenes and this interferes with the reaction.
My source of MnO2 would be from batteries.
I do have some KMnO4, if it can be used directly in this reaction.

I was thinking of the reaction between toluene + MnO2 + H2SO4 as mentioned in the first post, not the cinnamaldehyde --> benzaldehyde.

What is a thiotoluene? Is it something like this?
http://www.chemicalbook.com/ProductChemicalPropertiesCB15115...


I tried all the methods using tolune and cinamon and the truth is, you need all the right equipment in order to get it to work. It's just not fun if you have to impovise :(

vmelkon - 29-5-2013 at 14:01

Quote: Originally posted by questions  
I tried all the methods using tolune and cinamon and the truth is, you need all the right equipment in order to get it to work. It's just not fun if you have to impovise :(


I have equipment but I don't have lab grade chemicals.
I can prepare "activated MnO2" but I don't have high purity H2SO4 and toluene.

Bot0nist - 29-5-2013 at 15:03

In the p-toluenesulfonic acid thread, it was mentioned that thiol and other once common impurities are very rarely found in commercial toluene now a days, do to a change in the indrustrial manufacturing. In older texts and patents these impurities where a big concern, but are much less common now, IIRC.

Waffles SS - 30-5-2013 at 09:00

Benzaldehydes from Propenylbenzenes and Cinnamic Acids

has anyone ever tried this method?
http://www.erowid.org/archive/rhodium/chemistry/benzaldehyde...

ScienceSquirrel - 30-5-2013 at 09:21

Quote: Originally posted by Waffles SS  
Benzaldehydes from Propenylbenzenes and Cinnamic Acids

has anyone ever tried this method?
http://www.erowid.org/archive/rhodium/chemistry/benzaldehyde...


Have a look at the scale they are carrying the reaction out on and then calculate scaling it up to say 10g.

Waffles SS - 5-6-2013 at 21:15


Quote:

Benzaldehyde By dry distillation of a mixture of calcium benzoate and calcium formate


http://www.expertsmind.com/learning/benzaldehyde-assignment-...


Somebody has more information about this method?

Quote:


Calcium benzoate when pyrolyzed at 500 c produced
about equal amounts of benzene and diphenyl ketone


Mechanism of ketonic decarboxylation. Pyrolysis of calcium decanoate
Ronald A. Hites , K. BiemannJ. Am. Chem. Soc., 1972, 94 (16), pp 5772–5777
DOI: 10.1021/ja00771a039
Publication Date: August 1972
http://pubs.acs.org/doi/abs/10.1021/ja00771a039?journalCode=...




[Edited on 6-6-2013 by Waffles SS]

Random - 8-6-2013 at 02:04

I have read before on these decomposition methods, calcium salts may be used but I remember that iron ones may give out even better results.

I made iron benzoate and distilled a small amount of it with calcium acetate which should have produced acetophenone. It did produce something with a strong smell but I never had enough of it to check what it is.

Dry distillation of acetate with formate should produce aldehyde, but it would contain quite a few impurities and yields would be low. I'm up for the results if someone wants to perform this though.

Waffles SS - 13-6-2013 at 22:13

Quote:

1-Naphthaldehyde has been prepared from calcium α-naphthoate by distillation with calcium formate

Lugli, Gazz. chim. ital., 11, 394 (1881)

Banzaldehyde From Calcium Benzoate + Calcium formate

[Edited on 14-6-2013 by Waffles SS]

vmelkon - 3-7-2013 at 08:11

Hi guys,
One more question, I don't have any NaHSO3 so I guess I would use distillation. From what I read here, benzaldehyde gets destroyed when you distill it but it does work.

What product do you get when you distill?
I'm guessing water (from the sulfuric acid) and toluene comes over at first and then toluene and benzaldehyde and then mostly benzaldehyde as the temperature reaches 178.1 °C (1 atm).

Is that correct?
Perhaps I can reduce the pressure but the problem is leaks.

questions - 22-7-2013 at 10:07

You know what, they should give us a means for liking each others posts, just like facebook lol

questions - 28-8-2013 at 03:35

you know what, after looking at cyclonight's post I took out my dripper funnel and I got it to drip at a rate of 3 drops per second and then 40 minutes latter it was dripping at 13 drops per second and then 15 minutes latter it wasnt dripping at all.

Is it such that dripper funnels behave this way or is mine a reject ?

questions - 29-8-2013 at 00:03

I cant get my dropper funnel to keep a constant rate, last night it was one drop every 3 seconds and then like an hour later it was around 1 drop every 13 seconds. Is this common with dropper funnels ?

CycloKnight - 5-9-2013 at 08:05

Quote: Originally posted by questions  
I cant get my dropper funnel to keep a constant rate, last night it was one drop every 3 seconds and then like an hour later it was around 1 drop every 13 seconds. Is this common with dropper funnels ?


Yes, I had this problem. If you haven't already done so, remove the teflon/pp stop cock from the funnel, and using a razor blade, carefully cut a narrow V into the hole edge so that you get a more variable and controllable drip rate. Obviously this isn't possible if you're using a glass stop cock, but most are plastic these days.

testimento - 20-10-2013 at 15:01

I apologize for stupid question, but what comes when one reacts styrene with KMnO4? I cannot translate the image linked below into common name?

http://www.organicchemistry.com/wp-content/uploads/BPOCchapt...

http://www.organicchemistry.com/oxidation-reduction-of-organ...

thebean - 1-6-2014 at 16:02

Has anyone tried this method? The FC methylation of benzene is rather unnecessary considering toluene is easily available. They did switch brominating reagents from the start of the article, but I've seen several proven methods of producing benzyl bromide, so if you were to do that and then react it with hydrogen peroxide and ethanol it would probably work. They didn't include any sort of mechanism in the paper but I would guess that the water in the hydrogen peroxide solution hydrolyzes the benzyl bromide followed by oxidation of the alcohol using the hydrogen peroxide.

Metacelsus - 31-7-2014 at 14:39

I am attempting the electrolytic manganese-ammonium sulfate oxidation as posted by Cycloknight on page 3 of this thread, but I am noticing no change in color of the cell mixture. I am running at 1/12 of his scale and putting through 2 amps at 5 volts. The cell temperature, maintained by resistive heating, is 63 C. I am using platinum coated titanium electrodes. I have been running the cell for about 45 minutes, yet it remains stubbornly tan.

Are my electrodes messing stuff up (Pt overvoltage for oxygen 0.77 V, Pb overvoltage 0.81 V)? Can anyone else comment on this reaction?

I've replaced my anode with a graphite one, and I haven't noticed any difference yet.

I've switched back to platinum after my graphite anode was corroding (approx. 30 minutes). I've noticed a slight red-violet color appearing after checking it just now. I will leave the cell running overnight.


[Edited on 1-8-2014 by Cheddite Cheese]

Metacelsus - 1-8-2014 at 15:52

The cell seems mostly oxidized (based on color, and it is plausible for the amount of amp-hours passed), and the current has dropped to 0.3 amps. I will soon add toluene.

Never mind, it's still not done. I made an electrode out of solder (60% tin, 40% lead), and it works MUCH better than Pt.

Do NOT use a platinum anode for this experiment. It is not very effective.


[Edited on 2-8-2014 by Cheddite Cheese]

CuReUS - 13-9-2014 at 07:07

for making benzaldehyde from toluene,we could try this indirect route
first make phenylnitromethane

http://www.orgsyn.org/demo.aspx?prep=cv2p0512

at the bottom of the page,under "discussions",alternative methods are given(benzyl cyanide is not easy to get and hard to work with).the first one heats toluene with dilute nitric acid in a closed tube.this method was discussed by AndersHoveland in a previous thread-http://www.sciencemadness.org/talk/viewthread.php?tid=23542

("But the reaction with toluene is more complicated. A little known fact is that nitrogen dioxide actually reacts at room temperature (20 °C) with toluene to form phenylnitromethane, where a nitro goup is actually added to the methyl group of toluene.

"Phenylnitromethane has been prepared by the nitration of toluene with dilute nitric acid in a sealed tube."
Konowalow, Ber. 28, 1860 (1895).
(the sealed tube probably implies heating)

At higher temperatures, addition of two nitro groups on the same carbon predominates. "nitration of toluene with nitrogen dioxide at a temperature between 20 °C to 95 °C yields a mixture of phenylnitromethane and phenyldinitromethane")


the second method is to react benzenediazonium chloride with nitromethane.this reaction is easy,efficient and nitromethane is OTC.

after phenylnitromethane is made,we can perform the "nef" reaction to convert nitro to aldehyde.the yield is 70%

more about nef reaction

https://www.erowid.org/archive/rhodium/chemistry/nef.html

https://www.erowid.org/archive/rhodium/chemistry/nef.peroxid...

http://bitnest.ca/Rhodium/pdf/nef.reaction.review.2004.pdf





[Edited on 13-9-2014 by CuReUS]

Oxidation of benzyl chloride to benzaldehyde

Akira990 - 11-10-2014 at 03:41

I have found some research conducted by Republic of China, they claim they found an efficient and convenient method for the transformation of benzyl halides to coresponding carbonyl compounds. Example they presented is oxidation of benzyl chloride to benzaldehyde.. They claim they found that benzyl chloride could be oxidized to benzaldehyde by sodium nitrate (or potassium) in the presence of some catalyst at reflux....

I am interested if someone from this forum conducted this particular or similiar experiment and what are results.. ?

BTW sry for my English i am well aware i have more than few grammar mistakes..

Nicodem - 11-10-2014 at 05:01

I don’t see much of an advantage of using nitrates in the presence of "some catalyst" when already DMSO works well for the oxidation (DOI: 10.1021/ja01524a080). There are plenty of reports in the literature of oxidations of benzyl halides with various nitrate salts, but the yields are rarely comparably as good as the Kornblum or related reactions (like the oxidation with nitronates, amine N-oxides and hexamine). Unless the catalyst is something trivial and the yields are significantly better.
Quote: Originally posted by Akira990  
I am interested if someone from this forum conducted this particular or similar experiment and what are results.. ?

You appear to believe we are mind readers? "Republic of China" is not an author or scientific journal. I don't think anybody cares much about the grammar, but this is after all a science forum and therefore you are expected to use references. Please read the forum guidelines for more information.

CuReUS - 11-10-2014 at 05:20

i was wrong about the yield
its actually 94%:o (benzaldehyde oxime----->benzaldehyde)
benzaldehyde oxime will be the intermediate formed when phenylnitromethane is reduced via Fe/HCl according to the nef reaction
the only difficulty is to make phenylnitromethane using the method described by anders hoveland in my previous post

could someone get that piece of literature?

Akira990 - 11-10-2014 at 14:53

@Nicodem

My mistake.. catalyst used are acetic acid (AcOH) and polyethylene glycol 600 (PEG-600)

Yields depends of oxidant used NaNO2 (sodium nitrite) 87%, KNO3 (potassium nitrate) 89%, NaNO3 (sodium nitrate) 91%..

They also conducted experiment without catalyst(s) to show how much yields change..

About references, Ministry of Education of the Republic of China and Natural Science Foundation of Jiangsu province...

I can present more details if needed that concern experiment they conducted...

Akira990 - 14-10-2014 at 04:15

Here is the original document... Are this yields possible or not, they claim they got 90%... ?

Attachment: 54760-89674-1-PB.pdf (114kB)
This file has been downloaded 911 times


Hope this can assist.

DetachablePenis - 4-12-2014 at 09:55

Hello,

I constructed and ran such a cell some years ago (about 6 liters total volume of all reagents) and after much the same results as I read now here regarding low yields, it finally occurred to me that what was occurring was that the toluene was simply evaporating out of the top of the open cell before it was able to be reacted.

Upon sealing the cell and using a conventional condenser to manage pressure build up I was able to achieve the claimed yields.

If you look at the illustration in the old patent where they used several hundred KG of reagents, you can see that the 'tardis' or I guess even phallic shaped steel (I assume) reactor they used was a closed unit with a condensing pipe running from the top back down into the main body of the reactor.

Hope this helps everyone with their frustrations.

P.S. Computer power supplies connected in parallel are a cheap source of lots of amps if you can scrounge old discarded PC's which is very easily done as you may be aware.

I had about 10 or so CPU power supplies (about 3 plugged into each household circuit) in parallel at up to 35 amps a piece... I did not need any heating in the cell :) I did need thick, thick copper braid !

This regenerates fast.

Lead is easily obtained on the cheap from your metal recyclers, melted by a propane flame and poured onto ceramic tiles to create beautiful sheets of almost pure lead that you can cut up with tin snips or whatever for your anode etc.

Overhead stirring using a medium speed/high torque motor is a must and a bitch to seal. Failing going pro and purchasing a proper lab quality nipple setup, you can use the brass/s steel combo bearing out of the bottom of a food blender or similar appliance and use silicone or epoxy to jig it up.

Such a setup requires constant replacement of silicone or ptfe based lubricant or the sulfuric will eat the SS. You couple/join the SS center originally from the blender to a glass stirring shaft and paddle with a plastic "shaft coupler" from a hobby/model shop (looks like a hollow cylinder standing on its short end with two horizontal plastic hex head screws on the side that grasp the two vertical shafts) as anything else will work loose in my experience.

I am sure others will think of better ways, this was just what occurred to and worked for me.

Jimmymajesty - 27-3-2015 at 15:49

Hi Folks, I tried to oxidize some toluene today in the vapor phase. I started with around 300ml, after two hours run the liquid got a yellow tint. I will boil it with some NaOH tomorrow to see if there is any benzoic acid. The setup is as in the acetaldehyde thread the catalyst was copper wire.

Jimmymajesty - 28-3-2015 at 08:31

Hi there,

Instead of addig NaOH I poured some water into the flask and azeotroped out the organic phase.
The water in the pot smelled strongly of benzoic acid.
The water phase in the trap smelled benzaldehyde
The upper phase you would not guess... toluene.

So you can make benzaldehyde by this method I yet to do some more experiments to say how much.

But how would you extract 1-2w% benzaldehyde from toluene contaminated with benzoic acid?

With the bisulphite method or simply by using a column? Thanks!

IMG_3630.JPG - 590kB

Magpie - 28-3-2015 at 08:50

Jimmy you are really pioneering many uses for your catalytic device!

I am currently in the middle of an aldehyde synthesis which uses bisulphite for its isolation. I'll post the results soon (I hope).

Jimmymajesty - 29-3-2015 at 03:12

I like how easy is to replicate "complicated" industrial processes by some glass, kanthal and copper wire:)

When you isolate the aldehyde, be careful to fully avoid the alcohol carry over into the bisulphite solution since it would precipitate out the bisulphite before the adduct can form, as your experiment pointed out in the acetaldehyde thread.

Magpie - 29-3-2015 at 10:12

Quote: Originally posted by Jimmymajesty  

I like how easy is to replicate "complicated" industrial processes by some glass, kanthal and copper wire:)


Yes, we should do more of this. But you did hire a glassblower, right?


Quote: Originally posted by Jimmymajesty  

When you isolate the aldehyde, be careful to fully avoid the alcohol carry over into the bisulphite solution since it would precipitate out the bisulphite before the adduct can form, as your experiment pointed out in the acetaldehyde thread.


The bisulfite is added as a saturated aqueous solution. Since this is biphasic with the aldehyde I had to shake it vigorously for 1/2 hour (per procedure) to get the adduct to form. This appeared to work well.

[Edited on 29-3-2015 by Magpie]

Jimmymajesty - 31-3-2015 at 12:29

Magpie, is hiring a glassblower really such big a deal? In every town there are at least two, they always complaining not to have enough work so the one I usually go to quite happy when he sees me.

Magpie - 31-3-2015 at 14:02

No, hiring a glassblower is not a big deal and I encourage it. I have hired glassblowers to make borosilicate and quartz labware.

But finding one locally was not possible for me. I tried two. Neither would do work for private citizens, only business or institutions. They were concerned that the police would think they were helping drug cooks. :(

Jimmymajesty - 1-4-2015 at 00:41

IMHO it is not polite to ask someone why do you need this and that. I mean what is the point asking it? It is like being asked by the bank, why do you need money? You do not wana do sumthin illegal do you?

Glassblowers with this attitute better be avoided and I am sad that cooks made things so hairy in your town.

Jimmymajesty - 7-4-2015 at 12:47

Hi Folks,

I did another 2 hrs run in the weekend but this time, -seeing Magpie's salicyl aldehyde post- I isolated the benzaldehyde.
Started off with 328g Toluene, it was oxidized over copper wire for 2 hours.
Then 60g potassium metabisulphite was added. - nothing precipitated
The bisulphite was "neutralized" with 60g sodium carbonate (the solution became turbid + benzaldehyde smell)
Fractionated some gasoline: 60-75°C fraction was collected. This was used to extract the benzaldehyde ~0,5l
The C5-6 was distilled off on a water bath then I let air flow through the flask for 1 min to remove any traces of solvent.
The remaining liquid - benzaldehyde - was 1g
I let butane into the vial to inhibit the oxidation then capped.

Considering that after the bisulphite addition I got back 312g toluene so a total of 16g toluene was oxidized it is not so bad. I mean I can let the setup run for the whole weekend. That would yield 24g :D

Magpie - 7-4-2015 at 13:35

That's a slow production rate - but you have proved that it works in principle.

Did you shake the benzaldehyde/bisulfite mix for a long time? The mix is biphasic so the violent prolonged shaking is necessary.

Jimmymajesty - 8-4-2015 at 01:04

I know it is slow and it is only a proof that it may be possible to make decent amount of bzaldehyde by means of vapor phase oxidation. I think I have just made the most expensive 1g of benzaldehyde of all times, still I would call it a success.

Yes I shook it with bisulfite for 30min, then I shook the toluene phase with water to check for benzaldehyde smell and the result was negative. I think I lost some however during the extraction with alkanes. After shaking 100ml benzaldehyde+water with 100ml alkane the benzaldehyde smell was persent in the water phase every time.

Jimmymajesty - 9-4-2015 at 11:49

Hi again,

Now that the weekend is coming and I am antisocial enough to spend the time in the garage rather than outside I will try out the oxidation with CuO.

The copper oxide was prepared by anodic oxidation, the mica support with the kanthal wire was immersed into the CuO paste and dried with the filament, this was repeated couple of times. Of course the CuO is very porous so large chunks fell from the support during the assembling. It may all fall off when it gets into contact with toluene... we will see.

Anyway I think this as much chance as the benzaldehyde can get to form with this setup, so if I can not make more than last time I will not try it anymore.



IMG_3654.JPG - 399kB IMG_3655.JPG - 420kB IMG_3656.JPG - 358kB

Magpie - 9-4-2015 at 12:15

Very nice! As I've said before you are doing such original work: a real pioneer.

I have to ask: Was that element salvaged from a toaster? It sure looks like it.

I just happen to be working on a project where I might use the toaster element as a heater as it has a high specific resistance. I have measured it as 2.5Ω/10cm.
-------------------------------------------
Fresh results from the lab:

at 4a, R=2Ω/10cm; for 2a, R=1.7Ω/10cm

At 4a the wire is orange red, like in the toaster.
At 2a the wire has not changed color.

[Edited on 9-4-2015 by Magpie]

Jimmymajesty - 10-4-2015 at 13:37

Thanks Magpie,
It was not actually a toaster but your guess was very close it was in some hotplate.
What do you want to heat/pyrolyse with it?

So I did a run with CuO. As soon as I cranked up the power on the filament all the CuO turned to Cu in an instant. I wanted to operate under a mild condition, so I turned up slowly the wattage when the filament became incandescent I turned it down a bit.
Also I set the air load to such level that no Benzoic acid fumes were apparent at the outlet of the setup.
These setting yielded nothing... after 2 hours I took a sample from the toluene shook it with water, there was not any benzaldehyde in it.

So I think the benzoic acid vapors and the yellowing of the toluene indicates that the oxidation is going, without these you only wasting time.
This setup was not made to do this oxidation specifically, so I will come back with the good old horizontal reactor layout and see if I can make any uselful amount.
I have many improvements in mind, so wait for it!:)

Waffles SS - 4-10-2015 at 11:04

Reaxys search of all possible way for making Benzaldehyde from Toluene


Attachment: Toluene to Benzaldehyde.pdf (1.2MB)
This file has been downloaded 2321 times


Texium - 11-1-2016 at 20:57

I'm interested in performing the synthesis of o-nitrobenzaldehyde from o-nitrotoluene (for indigo synthesis). I've read through parts of this thread, and looked at some other resources from around the internet, but I am still not sure what the optimal procedure is. It seems like there are a lot of different ones with many variations and usually rather poor yields. Plus they're optimized for unsubstituted toluene and I don't know how they would work with the substituted version.

The sulfuric acid/manganese dioxide way sounds easy, but appears to be very unreliable in practice. The electrolytic procedures seem pretty good, but my electrochem skills are garbage so I don't think I'm going down that path. This one using chromium trioxide in acetic anhydride might actually be feasible if I am allowed to do it at school. Might an Étard reaction work for the substituted toluene? I'd prefer not working with chromyl chloride, but if it works well, I would consider it.

I'm simply not experienced enough to judge which procedure is best for me. I was hoping that someone who is more familiar with the contents of this thread, or with toluene to benzaldehyde oxidations in general might recommend a procedure that would fit my needs. I would just go and try a few different methods, but it was quite time consuming making and isolating the o-nitrotoluene, so I'm being very cautious.

Thanks.

Nicodem - 12-1-2016 at 08:21

The autooxidation of ortho-nitrotoluene, or the oxidation of its carbonanion by oxygen, can give ortho-nitrobenzaldehyde as the major product under proper conditions (alongside other products). There are numerous examples in the literature, though mostly in Chinese. For example, already stirring it in DMF at -10 °C can give a 30% yield (DOI: 10.3891/acta.chem.scand.25-3509). Oxidations with oxygen are catalyzed by transition metals and can give good yields (for example with Co(acac)2, DOI: 10.1055/s-0032-1318172; another one using MnSO4 is in DOI: 10.1023/A:1025824528577 and EP671381).

Alternatively, many published methods go trough a two step process of condensing with DMFDMA followed by oxidative cleavage to get the aldehyde (one such example is in DOI: 10.1080/00397911.2010.517366).

The oxidation with MnO2 in aq. H2SO4 is described in DE179589 (from 1899). It does not sound very safe as it is done in an autoclave reactor.

Texium - 12-1-2016 at 09:34

Ah, thank you Nicodem. I think I'll look into the manganese sulfate catalyzed one. Time to go see if it's on SciHub. :)

gsd - 13-1-2016 at 23:40

Controlled oxidation of alkyl chain of Toluenes (substituted or otherwise) to aldehyde by MnO2 in presence of H2SO4 is an extremely tricky process. Many old literature references talk about it in a very casual way as if the MnO2 is a pure reagent. In fact MnO2 being an ore has got extremely complex and complicated composition, crystalline structure and activity. "Unit Processes in Organic Synthesis by Groggins" describes it as a method of making benzaldehyde from toluene from old German reference. IIRC, the temperature is 40 Dec C and conversion stated is 20 %. When I attempted this reaction with local MnO2 ore (Manganese Ore India Ltd) having 80% MnO2, I got nothing. When heated to the reflux temperature, I got Benzoic Acid and no Benzaldehyde.

Substituted toluenes fare batter than toluene. I know of a company in India which makes Anisaldehyde (p-methoxy benzaldehyde) by MnO2 + H2SO4 oxidation route. They are one of the largest manufacturers of Anisaldehyde in the world and as a by product produce huge quantity of MnSO4 powder.

p-Cresol --> p-Methoxy Toluene --> Anisaldehyde

But the process is extremely delicate. They say that the MnO2 ore from only one particular mine does give them proper yields and a product free of impurity (of p-methoxy benzoic acid).

The synthetic MnO2s (EMD and CMD) - besides being very costly - are highly reactive and give benzoic acids rather than aldehydes.

Numerous methods in literature are given to "activate" an otherwise inert MnO2 ore. Some of them are very simple such as treating the ore with dilute Hydrochloric or Nitric Acid, but the results are still highly unpredictable and processes have to be validated on case to case basis. It is an ideal job for process development chemist.

gsd


byko3y - 14-1-2016 at 09:12

gsd, you are overemphasizing the problem. If you would try to use e.g. dead burnt ZnO as a catalyst for diol-urea esterification, you would obviously get 0% yield, because this kind of zinc oxide is almost completely unreactive. Iron-acid can reduce aldehyde to alcohol, but if you drop a nail into acid-aldehyde mixture, you will get no reaction. Just like manganese oxide ore is unreactive towards almost anything.
Do you know that polyethylene terephthalate is actually stable towards dillute hydrochloric or sulfuric acid? Despite the fact PET is an ester and should be hydrolyzed by acid.
If you drop a stone of calcite into an acid, it will take hours or even days to dissolve it, depending on the source and size of the stone.
There's 23 pages of discussion, I'm sure someone have already mentioned that you cannot use a regular MnO2 ore for toluene oxidation.
Benzaldehyde is one of the strongest oxidizers among the aldehydes, as well as they are good oxidation catalysts. To further oxidize benzaldehyde into benzoic acid, you need to fully exhaust the toluene-benzyl alcohol reagents.
Synthetic active MnO2 is easy and cheap to make, as well as the results of its application is predictable.
UPD: I've realized methylbenzene oxidation is not the same as a regular benzyl alcohol oxidation. Thus, MnO2 for the oxidation works or industrial production, but it's pretty much useless for laboratory preparative use. Here's the reason why: γ-MnO2 octahedral molecular sieve: Preparation, characterization, and catalytic activity in the atmospheric oxidation of toluene
MnO2 toluene oxidation.png - 43kB
As you can see, once you have benaldehyde in the reaction - it starts converting into benzoic acid, despite the fact that toluene is oxidized into benzaldehyde with very high selectivity.
I would recomment using of permanganate or some other reagent more selective reagent for the task. A Convenient Oxidation of Benzylic Methyl, Methylene, and Methine Groups with Potassium Permanganate/Triethylamine Reagent

[Edited on 14-1-2016 by byko3y]

S.C. Wack - 14-1-2016 at 16:37

Quote: Originally posted by gsd  
The synthetic MnO2s (EMD and CMD) - besides being very costly - are highly reactive and give benzoic acids rather than aldehydes.

Molinari specifies CMD as does Compt. rend. 634 (1901). I suspect the technique has a bit to do with it.

PS: And also IIRC in the relevant patents DE101221, DE107722, and FR276258.

PS2: US613460 indicates a CMD of vague hydration; there is no activation step: "Up to the present I have obtained the best results by the use of freshly-precipitated manganese binoxid or Weldon mud and sulfuric acid as the oxidizing agent"

[Edited on 15-1-2016 by S.C. Wack]

gsd - 14-1-2016 at 20:06

Quote: Originally posted by byko3y  

Synthetic active MnO2 is easy and cheap to make, as well as the results of its application is predictable.
UPD: I've realized methylbenzene oxidation is not the same as a regular benzyl alcohol oxidation. Thus, MnO2 for the oxidation works or industrial production, but it's pretty much useless for laboratory preparative use. Here's the reason why: γ-MnO2 octahedral molecular sieve: Preparation, characterization, and catalytic activity in the atmospheric oxidation of toluene

As you can see, once you have benaldehyde in the reaction - it starts converting into benzoic acid, despite the fact that toluene is oxidized into benzaldehyde with very high selectivity.


@byko3y here you are confusing between MnO2 as Catalyst and MnO2 as reagent.
The ref you have quoted uses γ-MnO2 as a catalyst for oxidation of toluene with molecular oxygen. To quote from the abstract that reference:
"A synthesized γ-MnO2 octahedral molecular sieve was characterized and used to catalyze solvent-free atmospheric oxidation of toluene with molecular oxygen. The γ-MnO2 showed excellent catalytic activity and good selectivity under the mild atmospheric reflux system at a low temperature (110 °C). Under optimized conditions, a 47.8% conversion of toluene, along with 57% selectivity of benzoic acid and 15% of benzaldehyde were obtained."

(BTW with 57% vs 15% selectivity in favor of benzoic acid, this is a process for acid with aldehyde as a welcome by-product)

I was discussing and commenting on the use of MnO2 as a reagent.

Quote: Originally posted by byko3y  

I would recomment using of permanganate or some other reagent more selective reagent for the task. A Convenient Oxidation of Benzylic Methyl, Methylene, and Methine Groups with Potassium Permanganate/Triethylamine Reagent


KMnO4 is a different ball game altogether. It is like American Football to me which I have never played.

gsd

gsd - 15-1-2016 at 05:47

Quote: Originally posted by S.C. Wack  


PS: And also IIRC in the relevant patents DE101221, DE107722, and FR276258.



Thanks SCW for the patents ref.

This is the patent referred in the Groggins book.

gsd

Attachment: DE101221C.pdf (185kB)
This file has been downloaded 593 times

Jimmymajesty - 29-1-2016 at 14:08

Hi there,

So my horizontal oxidation reactor seems to be complete.

Features:
Wattage controlled reboiler and preheating zone.
Good old -kanthal wire wound around Quartz tube- reactor.
Copper wire catalyst with very low residence time.
Glass thermowell to save the PTFE tape seal.
Air as oxidant

So I filled her up with ~0,5l previously pyrolysed toluene. The plan is to run it for at least 8 hours.
I am wondering how high can I go up to with temp at the preheating zone without damaging the PTFE tape seal at the end of the reactor. This can limit the oxidation. I have to go up to 400°C at least or I am just wasting my time.
Actually the plan is to see some incandescene at the copper then turn the heating down a lil bit till I see no light in the dark, then It should produce benzaldehyde 1/3 and benzoic acid 2/3.
Lot of questions here but they will all be answered in the coming days:)

WP_20160129_22_18_17_Pro[1].jpg - 1.9MB WP_20160129_22_18_36_Pro[1].jpg - 1.7MB WP_20160129_22_18_58_Pro[1].jpg - 1.6MB

Magpie - 29-1-2016 at 16:12

That's interesting work Jimmy. Can you give us some words of explanation to go with the pictures.

chemrox - 29-1-2016 at 17:02

Is there a way to de-energize the oxidation reax? 25% yield is not particularly auspicious. OAS: purification of benzal usually involves washing first with NaOH or Na2CO3 followed by bisulfite (aq) and distillation under aspirator vacuum. IMHO if you're pulling a vacuum N2 atmosphere can be neglected. @Jimmy: In the picture above left, the heating mantle is not sized for the flask and you might burn it up unless you pack foil around the flask. I like your inventiveness, reminds me of some of the stuff Rappaport used to show us.

blogfast25 - 29-1-2016 at 19:16

Quote: Originally posted by Magpie  
That's interesting work Jimmy. Can you give us some words of explanation to go with the pictures.


Hear, hear!

I'm particularly interested in the tubular reactor: wattage and type of resistor.

Jimmymajesty - 30-1-2016 at 07:51

So... Toluene boils and it goes up in 1m long glass tube, at half way up is a thermometer to monitor the vapor temp, this long distance may prevent benzaldehyde carryover since it would be oxidized to benzoic acid or pyrolysed into benzene if it would hit the copper again. At the top of the column (at the inlet of the quartz tube) is the air inlet, air is supplied by an aqua pump.
The reactor is 1m long quartz tube the copper wire is at half way, before this is some raschig to help toluene mixing with air.
There is a grounded glass joint insert at both end of the reactor that were accomodated and sealed by PTFE tape, that is the reason why i have to monitor the temp at the end.
The toluene boils somewhat separates from the heavies on its way up, then it mixes with air, preheats by means of kanthal wire, hits the catalyst, cools somewhat, then completely condenses in the condenser, flows back into the 2l RBFL, so basically the content of the RBFL is never gets into contact with air.

So the 8hr run has started about 1 hr ago, the toluene boils so there is 3drop/sec at the condenser (may be too high) the temp at the end of the reactor is 250°C. I am a bit skeptical that I will be able to recover any useful amount of Benzaldehyde, but who knows, the copper is working though evidenced by the color change at around 230°C. As I understand it, when the CuO loses its O2 and its converted back to Cu or Cu2O indicated by the color change means the copper started to act as a hydrogenation or oxidation catalyst. In this reducing atmosphere Cu2O oxidizes the toluene with one molecule oxygen and it keeps being regenerated by molecular O2 from air.

There are benzoic acid crystals on the wall of the reactor after the catalyst so it kinda works.

The wattage of the kanthal on the reactor is 1500W.
Yeah I often char things... mainly on purpose:) thanks for the advice though!

IMG_3845[1].JPG - 451kB

[Edited on 30-1-2016 by Jimmymajesty]

[Edited on 30-1-2016 by Jimmymajesty]

[Edited on 30-1-2016 by Jimmymajesty]

blogfast25 - 30-1-2016 at 09:36

I'm certainly interested in your results.

You don't seem to have a lot of oxygen in your system though: maybe about 0.008 mol of O2? Or am I missing something?

Magpie - 30-1-2016 at 09:52

Where is the excess air (N2) vented?

Did you wind the kanthal or did you buy/salvage it as a coil?

Do you have a reference for this method or is it your invention?

;)

Jimmymajesty - 30-1-2016 at 11:13

blogfast you are right, the O2 concentration in the reactor is very low. 10ml of air to 3-5 drop of toluene, but this is exactly hat you want, too much O2 and the CHO goes to COOH or even CO2 & H2O

Magpie, of course it was salvaged, it is from an old air heater, the kanthal wire is so old that I tried to wind out the other one and it broke in many points so I just left this one as it was.

Actually I did not find any ref for continuous recycling lab procedure, all the patents around describing yield based on one pass due to high conversion rates, also note that every patent describes net oxidizing air+toluene mixtures, so in my case benzoic acid formation should not be significant, still... copper can facilitate in its formation even in net reducing mixtures because its too strong catalyst if you only want aldehyde. Molybdenum trioxide would be much better, or tungsten.

So I have many ideas if this experiment fails.
1, Decrease the toluene flow and ramp up temps in the current design
2, Increase toluene flow and ramp down temp... you never know:))
3, oxidation with heated copper filament
4, oxidation with heated tungsten filament
5, oxidation with heated molybdene filament

The N2 exhaust point is at the end of the condensor, you can see it in the first picture, it is the highest point of the setup.

[Edited on 30-1-2016 by Jimmymajesty]

Jimmymajesty - 31-1-2016 at 13:42

After the run, I let everyting cool, then take out 5ml yellow toluene, shook with 25ml water, then I let it settle and smelled the watery phase to find out there is hardly any benzaldehyde in it, as a result I bypassed "Idea 1 and 2".

I did a run today by "idea 3" but with a vertical reactor design.
After 1hr I sampled it and the presence of benzaldehyde was evident.

So I am gona run the vertical reactor for a whole weekend sometime.
Damn I wish I had more time for chemistry...

Jimmymajesty - 12-3-2016 at 10:23

Hi,

I gave it a decent try today. The toluene vapors went through a column which provided some degree of separation. Air inlet connection, then raschig packing to help air mix into the toluene vapor, then kanthal wire wound around a mica sheet and copper oxide pellets (see pic). After the reaction all condensable liquid went back into the flask. This was basically the setup used at my first attempt but an improved version.

I added 50ml water to the toluene to increase the vapor pressure of the benzaldehyde after the reaction zone. I gradually adjusted the voltage on the kanthal to intitiate self pyrolysis of toluene, then decreased it a lil bit and adjusted the air inlet to be ~2ml/sec.

I sampled the condensed liquids from time to time shook it with water then smelled the watery phase. I went from the above condition till the kanthal was orange (~5sampling) to find out there was not any benzaldehyde in the condensate.

Now I am kinda puzzled since this means that a simple ethanol => acetladehyde setup with brute force produces more benzaldehyde than the current one...?! I do not really know how to improve from here. I will sample the watery phase in the flask when it cools, but I am skeptic that it will contain any benzaldehyde.

IMG_3855.JPG - 537kB

Jimmymajesty - 13-3-2016 at 16:50

So... I also tried out copper plated kanthal wire and manganin as the heating element. Chunks of diesel catalytic converter and copper sponge as the catalyst. Countless air and wattage settings but not a single molecule of benzaldehyde, during the 12hours torturing the initially yellow toluene turned into a somewhat viscous black crap, so I managed to find a new way to turn half a litre toluene to useless crap.

I took a picture to show how hard I kicked the toluene molecules in the ass, there is black tar coming down as condensate (bottom-right side small black bulb). This run was with diesel catalyst chunks, the condenser filled up with uncodensable myst which I believe was benzoic acid, still no benzaldehyde...

WP_20160306_18_49_11_Pro.jpg - 1.8MB

PHILOU Zrealone - 15-3-2016 at 05:30

Benzaldehyde is sensitive to auto-oxydation into benzoic acid

Also you may request this document in document request section:

THE PYROLYSIS OF BENZALDEHYDE AND OF BENZYL BENZOATE

Charles D. Hurd, C. W. Bennett
J. Am. Chem. Soc., 1929, 51 (4), pp 1197–1201
DOI: 10.1021/ja01379a030
Publication Date: April 1929
First page

chemrox - 15-3-2016 at 17:19

Quote: Originally posted by Jimmymajesty  
Magpie, is hiring a glassblower really such big a deal? In every town there are at least two, they always complaining not to have enough work so the one I usually go to quite happy when he sees me.

It can be. I'm in a depressed part of the us and a lot of glassblowers have gone under. To make matters worse the local U is a private rich kids school and they don't repair any glassware and don't have very creative chemists. The guy I have to use is 60 miles away and spends a lot of his time on ebay.
The other guy does quartz for the med school and charges too much for simple mods and repairs.

Jimmymajesty - 21-3-2016 at 13:53

I have other ideas that I want to try out like, oxidizing the toluene with NO2 I just have to take a break when handling these aromatics, gas mask or not I just can not avoid getting some when handling it... also when I try to identify the product my only instrument is my nose and my gf smelled something gasoline-ish in my breath when I spent the whole day in my lab... my fume hood sucks like a hooker since it can only accomodate a test tube confortably, so most of my time goes with silver recovery from relays and such benigh things.

As for the glassblower mine just diagnosed with cancer so I do not really know who to turn to if he can not work anymore... so I feel your situation. I always use the local flea market search engines with the words "lab, labware, lab instrument, flask, chemistry, chemical, etc. from week to week there is a hit and usually the seller do not know what they are selling so the glass comes fairly cheap I bought this on the weekend for 4USD do not know what to do with it but it sure looks lovely isnt it?:)

IMG_3859.JPG - 541kB

lolohydrat - 19-5-2016 at 12:12

Which metal can you use instead of lead?

Air oxidiser

Chemetix - 19-10-2016 at 14:06

I have wanted a way to make p tolualdehyde fairly easily, this post using air oxidation schemes sounded attractive as a semi industrial route. What I found was that there are limitations to the air oxidation schemes. Perhaps this might be useful in some way for the production of the TM on this forum.

"The autoxidation of p-xylene is known to proceed through a free radical process. The Mn(III) and Co(III) metals alone are not strong enough oxidizers to start the radical chain reaction, but instead initiate it by forming bromine radicals from the ions in solution. These bromine radicals then decompose hydroperoxides that are ligated to the metals as well as abstract hydrogens from the methyl groups on p-xylene to form free radicals and propagate the reaction. The following are the proposed initiation, propagation and terminations steps for the first of four oxidations involved in the autoxidation:" [https://en.wikipedia.org/wiki/Terephthalic_acid]

An initial study was run using a heated catalyst surface with different transition element oxides and a promoter. p-xylene vapour and air were passed through the reaction zone and condensed then returned to the flask. Runs were about 6hrs each with 50mls p-xylene, and the flask then distilled to observe the quantity and nature of the residue. The quartz reactor (from an old heater) has a nichrome filament inside and a glass fiber soaked in catalyst wrapped on the outside and held in place with nichrome. The catalyst surface reached a maximum temperature of 350C.

In all cases only a very small amount of oxidised residue was formed, 5ml at the most, catalysts tested were- in order of perceived activity: V2O5/FeCl3, Co2O3/FeCl3, Ni2O3/FeCl3, Fe2O3/FeCl3, SnO/FeCl3.

The quick and dirty conclusion is that surface areas need to be huge in order to generate any meaningful quantity in a reasonable time. Optimising the choice of catalyst/promoter and cleaning the inlet air to prolong the catalyst activity is a secondary concern with regards to the practicality of the scheme.


V2O5 sml.JPG - 173kB SchemeSml.JPG - 94kB ReactionZoneSml.JPG - 160kB ReactionSml.JPG - 151kB

The Volatile Chemist - 12-12-2016 at 18:17

Quote: Originally posted by Jimmymajesty  
I have other ideas that I want to try out like, oxidizing the toluene with NO2 I just have to take a break when handling these aromatics, gas mask or not I just can not avoid getting some when handling it... also when I try to identify the product my only instrument is my nose and my gf smelled something gasoline-ish in my breath when I spent the whole day in my lab... my fume hood sucks like a hooker since it can only accomodate a test tube confortably, so most of my time goes with silver recovery from relays and such benigh things.

As for the glassblower mine just diagnosed with cancer so I do not really know who to turn to if he can not work anymore... so I feel your situation. I always use the local flea market search engines with the words "lab, labware, lab instrument, flask, chemistry, chemical, etc. from week to week there is a hit and usually the seller do not know what they are selling so the glass comes fairly cheap I bought this on the weekend for 4USD do not know what to do with it but it sure looks lovely isnt it?:)


That's a sort-of steam-distillation bulb/head. I've seen it in Vogel's OChem. Basically, you stick the long part into a flask where the boiling solution surrounds the test-tube-like bulb with the glass tube inside. The vapors go down into the 'test tube' via the curved glass tube, and bubble through there (which should already contain the liquid you are to steam distill). They exit containing what is to be stilled over with the vapors at the top ground glass port. The stopcock is to ensure that the process of cooling doesn't suck the compound you are steam distilling into the solvent (or vice versa, I forget).

Booze - 6-5-2017 at 10:41

Could you use nitric acid as an oxidiser?

moonbeamstudio - 15-9-2017 at 01:30

A common mistake in all these atemts posted here is that activated MnO2 has to be used!! It is simply done with MnSO4 and Potassium manganate(VII)...

I have the procedure if someone wants it.
Greetings to you all, freaks! :))

sykronizer - 16-12-2017 at 19:14

I remember reading about the air oxidation of Toluene to benzaldehyde. The catalyst was V2O5 and the the Toluene vapor and air was sent through that quickly with the catalyst being a tube that was heated to 700 Celsius...I'm wondering if one could simply use a high Vanadium-steel tube instead of any other fancy catalyst. Surface area is not an issue when you have a vapor mixture buzzing around in there at a dull red heat, and it needs to move through pretty quickly too other wise pyrolysis will just wreck Toluene not to mention the aldehyde. Yields are low but the range of byproducts were minimal, the parameters were optimized so the rest of the process was a distillation and recycling of the toluene. But, I doubt this process is still used industrially given the availability of other feed-stocks and lower energy cost's required for the conversion, such as side chain halogenated Toluene, but as everyone knows that process is another example of what works on large scale is nothing but an absolute nightmare on the lab bench, and I suspect tweaking this air oxidation method may also be a bit like that.

Preparation of (substituted) benzaldehydes

KiWiki - 1-1-2018 at 09:38

Did someone try one of the Drake and Perkin methods:

1. Electrolytic oxidation of toluene, ortho-, meta-, para- xylene in acid solution is a very easy way to prepare the corresponding benzaldehyde. However, in alkaline solution toluene and meta-xylene will oxidize to carbon dioxide and water.
Source: Trans. Faraday soc., 1905, 1, 31, 251

2. Oxidation with chromyl chloride (see preparation in attachment) to the corresponding benzaldehyde. *
Source: Herbert Drake Law, Frederick Mollwo Perkin, "Oxidation of Hydrocarbons of the benzene series" , J. Chem. Soc. 91, 258, (1907)

*the modern alternative for chromyl chloride might be PCC in Silica gel for this method. I don't have access to these full articles... :(
Are there already experimental results that cover these two interestring methods?

Sciencemad.png - 257kB

EDIT: (by Antrax):
Perform the electrochemical oxidation with 200 to 300 mL acetone to dissolve toluene or xylene. The addition of sodium bisulfite prevents further oxidation of benzaldehyde. Use 5% to 10% 200 mL H2SO4.
70 A/h /50 g toluene or xyl. Yields are not great as sulphate ions stick to the anode and the fact that benzyl alcohol is formed.

Yields are not higher then 20%, I don't report exact experimental yields and sometimes I even don't give these yields for academic research.

[Edited on 2-1-2018 by KiWiki]

sykronizer - 30-1-2018 at 15:50

The Toluene of commerce here in NZ and Oz is contaminated with some sulfur compounds, a sulfuric acid wash gives a dark red layer, so what ever method of oxidation we may try, I strongly suggest a clean up of the Toluene first.
After a few failures I am going to have another go at the Etard reaction, using methylene chloride as the solvent, although it's low boiling point is not ideal. It is reasonably convenient because the chromyl chloride can be prepared without having to resort to using a retort, for distilling it off. A word of caution though, do not take short cuts with solvent amounts, ie; make certain you are using at least a 25 percent dilution of the chromyl chloride to solvent, ditto for the Toluene as well, and constant stirring and cooling. My initial run was a disaster, I was too reckless, and added the chromyl far too quickly, which resulted in a sudden rise in temperature, that combined with my low boiling point solvent resulted in a stirred suspension of the adduct going from liquid to solid in about 1 to 2 seconds immediately followed by a mild explosion that covered about 4 square meters of green lumpy crap , I was uninjured thanks to my safety glasses.

phenyl - 6-2-2018 at 03:54

probably the easiest synthesis from toluene, is direct oxidation using persulfates salts and a Fe+2/Cu+2 catalyst to promote oxidation in the biphasic reaction mixture. the primary alcohol co-solvent seems to somewhat prevent over oxidation too. Can't remember the original reference but it's probably here on SM somewhere. The product needs to be purified by adduct or vacuum fractionation to remove excess toluene, but it does work with subst. toluenes with a reasonable yield.

(modified from original?!)

purified toluene (7.6 g, 0.082 mol)
ferrous sulfate (110 mg)
cupric acetate (80 mg)
ammonium persulfate (45 g, 0.197 mol) dissolved in ~150 mL DH2O
primary alcohol EtOH or MeOH (58 mL total)

the catalyst is dissolved in DH2O (35 mL) and ethanol (8 mL), to this toluene is added. persulfate is dissolved in water with ethanol (50 mL) and is added to an equalised addition funnel. the mixture is heated to 65-70 degrees celsius on a water bath with good stirring, before addition is started. addition should take 45 min with refluxing being continued for ~1-2 hrs after addition. the aqueous layer is separated and washed with 3x25 mL DCM which is combined with the organic layer and the DCM was evaporated.

yield ~ 8 g crude benzaldehyde (slightly yellow in colour)
* product is usually colourless if an inert atmosphere is used

j_sum1 - 6-2-2018 at 04:34

This is nearly the same procedure quoted on the first page of this thread. My attempt recently was not really a success but with a bit of perseverence I should get there. See video on my yt channel if interested.
I need a better source of persulfate.

phenyl - 7-2-2018 at 01:01

yeah it is, just recalculated based on NH4 rather than Na, with ethanol instead of methanol. PCB etchant is usually the pure ammonium salt (~98%), it's easy to find at any good electronics store. on a side note some acetaldehyde is produced as a side product in the reaction.

also benzaldehyde is fairly soluble in methanol/ethanol aqueous solutions.
"Ethanol increases the solubility of hydrophobic substrate such as benzaldehyde"

Breslow, Ronald, and Richard V. Connors. "Quantitative antihydrophobic effects as probes for transition state structures. 1. Benzoin condensation and displacement reactions." Journal of the American Chemical Society 117.24 (1995): 6601-6602.

[Edited on 7-2-2018 by phenyl]

[Edited on 7-2-2018 by phenyl]

j_sum1 - 7-2-2018 at 01:55

Alas. There is no such thing as a good electronics store where I live. But Na2S2O8 is available in hardware stores as a pool oxidant. Apparently it is less pure than I thought.

sykronizer - 7-2-2018 at 23:50

I have tried that persulfate method, sticking exactly to the method and reagents and all I got was the detection of that horrid carcinogenic formaldehyde..and lots of it. I really do have to wonder about this procedure, I mean, doesn't it seem obvious that this specific system, the persulfate and iron/copper couple will oxidize methanol a damn site quicker than it will Benzyl Hydrogen's ? . I also tried changing the metal couple, I used silver Nitrate alone, silver nitrate and cupric also no go...just more stench of embalming fluid...So what appears easy on paper in terms of procedure and ease of reagent acquisition is not all it's cracked up to be. Most refs that detail different oxidation methods, at least older material, seem to suggest that the Etard is always consistent in giving a yield, not necessarily a repeatable yield, but at least a REPRODUCIBLE yield, it's really been bugging me for a while, how much trouble this one synthesis has been for me.

Chemetix - 8-2-2018 at 14:23

The Maggione patent using persulphate redox pair co catalyst is obviously leaving a lot out of the patent if it works at all. I left out th e lower alcohol solvent and got some yield, but nothing like the patent. Perhaps PTC and water? I was going to try it but never got around to it.

S.C. Wack - 8-2-2018 at 16:08

Walling et al. had some peroxydisulfate success with aq. acetonitrile or acetic acid (acid giving benzyl acetate), at microscale naturally. K10 montmorillonite and KMnO4 is also supposed to work (better on benzyl alcohol obviously), but where to find some.

JJay - 31-3-2018 at 19:23

Entirely out of academic curiosity, has anyone seen any papers stating that someone managed to isolate benzaldehyde from a chromium (VI) oxide peroxide oxidation of toluene? It seems to me as though it would be possible to do it in reasonable yield, and it can't be that hard, right? But all of the work I have seen on the subject is theoretical.
 Pages:  1  ..  4    6