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Author: Subject: toluene --> benzaldehyde
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[*] posted on 6-1-2012 at 07:51


I love benzaldehyde, not just for it's broad uses, but because of it's signature smell and oily texture, it's also very expensive in australia as well I hear.

I've been doing a lot of research into the reaction of cinnamon aldehyde in a boiling solution of water with ph 11 to 13 and antifoaming agent. I know this thread is all about toluene but I'm posting it here because more people ot at this thread, also cyclonight made many posts and no one knocked him for doing so.

Anyway, I've tried the experiment and have found that the more benzaldehyde is made, the more tar is formed in the reaction.
After an 7 hour reaction of 200ml of cinnamon aldehyde in a 2L solution of boling water with a steady ph of 12.5 and antifoaming agent, only 30% was benzaldehyde, 20% was unreacted cinnamon and the other 50% was all this tar shit.

I think that the aceteldehyde is reacting with the benzaldehyde in this base solution and that is what is making all this tar shit. Because I don't believe that this tar shit is a product of the cinnamon turning into benzaldehyde and acetaldehyde, I think that shortly after the benzaldehyde has formed, it reacts with the acetaldehyde that has formed. I cant think of any other explanation and I certainly dont think that the benzaldehyde is reacting with the cinnamon, could it????

If it is such that the formed benzaldehyde is reacting with the formed acetaldehyde, what can we put in place to stop or even minimise this from happening?




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[*] posted on 6-1-2012 at 08:22


Yep, the acetaldehyde is definately reacting with the presious benzaldehyde thats fored in the reaction with cinnamon oil in boiling water with ph 12 as illustrated in point 2)

http://web.pdx.edu/~wamserc/CH332W97/homework/H11ans.htm




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[*] posted on 17-2-2012 at 06:15


Quote: Originally posted by questions  
I love benzaldehyde, not just for it's broad uses, but because of it's signature smell and oily texture, it's also very expensive in australia as well I hear.

I've been doing a lot of research into the reaction of cinnamon aldehyde in a boiling solution of water with ph 11 to 13 and antifoaming agent. I know this thread is all about toluene but I'm posting it here because more people ot at this thread, also cyclonight made many posts and no one knocked him for doing so.

Anyway, I've tried the experiment and have found that the more benzaldehyde is made, the more tar is formed in the reaction.
After an 7 hour reaction of 200ml of cinnamon aldehyde in a 2L solution of boling water with a steady ph of 12.5 and antifoaming agent, only 30% was benzaldehyde, 20% was unreacted cinnamon and the other 50% was all this tar shit.

I think that the aceteldehyde is reacting with the benzaldehyde in this base solution and that is what is making all this tar shit. Because I don't believe that this tar shit is a product of the cinnamon turning into benzaldehyde and acetaldehyde, I think that shortly after the benzaldehyde has formed, it reacts with the acetaldehyde that has formed. I cant think of any other explanation and I certainly dont think that the benzaldehyde is reacting with the cinnamon, could it????

If it is such that the formed benzaldehyde is reacting with the formed acetaldehyde, what can we put in place to stop or even minimise this from happening?


Hey mate,
been quite a while since I did this reaction, but I recall it quite well. You seem to be getting an awful lot of tar, might I ask how much steam you are putting through the reaction vessel? Was the cinnamonaldehyde pre-vacuum distilled prior to use or it it straight cinnamon bark oil?

As mentioned in PM, I made about a litre of refined, vacuum distilled benzadehyde in a few days, using not much more than a litre of cinnamonaldehyde, maybe 1.25 litres or so.
I didn't experience anywhere near the level of tar you've observed.
The benzaldhye WILL turn into tar if left stagnant in the pH 12 reaction vessel, this is why a large volume of steam is required, the steam removes the benzadehyde almost immediately as it is formed. However, no tar was produced in the condensate vessel where condensate, acetaldehyde, benzaldehyde and unreacted cinnamonaldehyde collected together.
I recall that for each 200 ml or so batch of cinnamonaldehyde, I put enough steam to condense into about a gallon of condensate (well, I used a 1L volumetric flask, filled about 4.5 times). Each 1 L volumetric flask was solvent extracted to recover the goods, but a large percentage of the aldehde was either sitting on the surface or would sink depending on the ratio of cinnamon to benzaldehyde. I recall that for each 1L flask of condensate fully filled, before solvent extracting, about an inch or two of free aldehyde would sit in the narrow neck, sometimes sinking if shaken.

The pooled solvent extracts where combined, DCM boiled off, then vacuum distilled to yield ~80% overall yield of benzaldehyde. Don't recall exactly, but it was around that mark - yields were very good.
Unreacted cinnamonaldehyde was recycled (this was the left over from the vacuum distillation).
To decide on the cinnamon aldehyde drip rate, match the drip rate with the rate of steam generation.
In other words, (for example) if it takes 4 hours to produce a gallon of condensate, then drip your 200 ml into the boiling hot pH 12 solution over 4 hours. The faster the rate of steam generation (and shorter reaction time) the better. I used a converted pressure cooker, which produced enough steam to limit each batch to a few hours. The reaction and steam distillation is finished when the condensate no longer smells of aldehyde, which isn't long after the last drop of cinnamonaldehyde is dripped into solution. Can't quick recall the mass flow rate I used, but I can tell you it was the maximum that would be allowed before the steam carried over bubbles and solution into the vigreux column, at times the bottom of the column would get wetted with bubbles, but would all separate before reaching the top (so as not to contaminate the condensate). The steam flow will be high enough to make the solution very turpid and noisy, it will cause the table top to vibrate as the bubbles knock the solution around quite a bit, just as if you inserted a straw and blew as hard as you could - that's the level of steam flow you need. :)
The only way I could get that level of flow without it shaking the equipment to pieces, was to take a glass tube about 10" long, heat the end to redness, and bend it into a fish hook shape (but taking care not to block the end). This causes the steam to flow UPWARDS, from the *bottom* of the solution. Fascilitating a nice flow, whereas simply putting a straight glass tube doesn't work too well.

Ck








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[*] posted on 24-2-2012 at 06:47


Cyclonight is clearly the most intelligent person on this site.



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[*] posted on 2-4-2012 at 06:36


I had performed so many unsuccessful trials with persulfate oxidation of toluenes that now that I've succeeded I feel obliged to share :)

The procedure is somewhat of an arithmetic average of two patents, US4146582 and US7273954.


Apparatus:

500 ml three-necked flask
addition funnel
mechanical stirrer made of a car window raiser's motor (take a note of this fact, such a motor makes the most perfect mech stirrer that a hobby chemist can only dream of)
water bath


Reagents:

30 mls (244 mmole) p-xylene
100 mls DMSO
cupric acetate monohydrate 4.5 mmole in 10-15 mls water
ferrous sulfate heptahydrate (gardening grade) 1.5 mmole

Temp. raised to 70 C and with intensive mechanical stirring 128 g (561 mmole, 2,3 eq.) of ammonium peroxodisulfate (NH4)2S2O8 in 180 mls water was dripped in during 2 hrs, keeping the inner temperature at 70 C (the rxn is exothermic, the bath's temp. needed to bee kept at 60-63 C). Stirring continued for another hour after the addition was finished.

The RM was chilled well, saturated w/salt and xtracted with 4*50 mls EtOAc. Extracts washed with 10 mls 5% NaOH, then brine, diluted w/50 mls IPA, combined with 150 mls saturated aq. Na2S2O5 anв 10 g Na2S2O5 powder. With intensive mech stirring the temp. was raised to 45 C during 30 mins. The lower aq. layer was discarded and upper floating layer of precipitated adduct was filtered (filtration was nice and easy), washed on filter with 3*25 mls IPA dried and weighed (51 g).

The adduct was dissolved in 200 mls hot water, quenched with a slight xcess aq. NaOH and pH was carefully brought to weakly alkaline with dilute HCl (this is to aid the extraction, which is otherwise a mess). The mixture was cooled, saturated with NaCl and xtracted with 3*50 mls DCM. Extracts washed w/brine, dried, solvent removed on waterbath.

The yield was good 19.5 mls (67%) of para-tolualdehyde, which was almost colorless (!) and distilled in vacuo almost wholly to leave but slight driplets with sulfidic smell.

All of the further manipulations with this aldehyde were also quite successful ;)



Greetings from HyperLab,

Antoncho

[Edited on 2-4-2012 by Antoncho]

[Edited on 2-4-2012 by Antoncho]

[Edited on 2-4-2012 by Antoncho]

[Edited on 2-4-2012 by Antoncho]
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[*] posted on 20-4-2012 at 06:21


Ok I have been cooking some benzaldehyde stuff recently. First I just mixed 300 grams of toluene, 700 grams of 65% H2SO4 and 90 grams of MnO2 and stirred and heated it for a while and then distilled the stuff to the point the H2SO4-MnO2 - gunk turned pale brown. In the receiver flask there formed two layers. At the beginning only the upper layer distilled, but when I kept going, the lower layer began to form. I havent yet been able to determine what the lower layer actually is, but it doesnt burn and it boils at 100C and its oily and clear liquid, which will dissolve water. I have gained about 500ml of this stuff.

Both layers smell a bit of almond as an evidence of benzaldehyde existence. The upper layer obviously consists of toluene, possibly some water, and benzaldehyde(??). I concentrated it via distillation and yellow oily liquid was left in the pot, which has strong almond smell. Only some 10mls of it is being around.

Now the second procedure: put 1:1 molar ratio of sulfuric acid and manganese dioxide in pan, add a bit of water and boil the shit until white fumes appear, let it cool and then add 1:1 amount of toluene and enough sulfuric acid to dissolve all the solids remained from the 1:1mol mixture. I left this stuff react for 24 hours and a yellow layer separated over the mno2-h2so4-gunk. Then added lots of water for steam distillation and distilled up the stuff. First came off the upper layer with homogenous solution, but then the "heavy stuff" began to drip again, when the upper layer was completely distilled. Obviously this stuff that accumulates to the bottom of the receiver flask is some sort of sulframic or other stuff which forms with water, h2so4 and mno2 existence.

Ok, now I've got pots around with almond and toluene smelling shit which I want to separate the remainings of benzaldehyde off. I understand that this can be accomplished with sodium bisulfite which I will get next week. The process for me is unknown so far, but what I have read it simply requires putting excess bisulfite to form adduct with the benzaldehyde, then filter this solid shit off, washed with concentrated bisulphite water solution and then reformed with 10% sodium bicarbonate solution. Am I correct with this one?

I'm not definitely sure what the yields are or what the hell is actually going in the distillery but I'm gonna find it out soon. Luckily the H2SO4, MnO2 and toluene are quite cheap and OTC for me so a little lower yield of benzaldehyde is not that big problem.
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[*] posted on 23-4-2012 at 18:23
AC electrolysis


Just found this - I don't think it's been already mentioned (though I may be wrong)

ELECTEOLYSIS WITH ALTEBNATING CURBENT.

Electrolytic oxidation may be moderated by superimposing alternating current upon direct current . 0. Eeitlinger1 has shown that alternating current diminishes the overvoltage at the anode during electrolysis, and it is thus possible to prepare oxidation products which are not easily obtained by direct current only. Ethyl and propyl alcohols give aldehydes, whereas when oxidised with continuous current only, the principal product is the corresponding acid.

Prom toluene suspended in dilute sulphuric acid (density 1*22) it is possible to obtain benzaldehyde and benzoic acid if A.C. be superimposed upon D.C., whereas with D.C. only, the toluene is completely oxidised to carbon dioxide and water. Similarly p-benzaldehyde sulphonic acid is obtained from toluene sulphonic acid.

By the same method sulphuric acid may be made to yield a considerable quantity of ozone, whilst ammonia may be oxidised to nitrous acid (40 per cent, yield) without the formation of nitric acid.

These investigations indicate that we have here a valuable means of controlling oxidation processes.

1
Zeitsch. EleMrochem., 1014, 20, 261.

taken from THE MANUFACTURE OF CHEMICAL S BY ELECTROLYSIS (sciencemadness library)
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[*] posted on 25-4-2012 at 18:44


Quote: Originally posted by learningChem  
Just found this - I don't think it's been already mentioned (though I may be wrong)

ELECTROLYSIS WITH ALTERNATING CURRENT.

Electrolytic oxidation may be moderated by superimposing alternating current upon direct current . 0. Eeitlinger1 has shown that alternating current diminishes the overvoltage at the anode during electrolysis, and it is thus possible to prepare oxidation products which are not easily obtained by direct current only. Ethyl and propyl alcohols give aldehydes, whereas when oxidised with continuous current only, the principal product is the corresponding acid.

From toluene suspended in dilute sulphuric acid (density 1*22) it is possible to obtain benzaldehyde and benzoic acid if A.C. be superimposed upon D.C., whereas with D.C. only, the toluene is completely oxidised to carbon dioxide and water. Similarly p-benzaldehyde sulphonic acid is obtained from toluene sulphonic acid.

1
Zeitsch. EleMrochem., 1014, 20, 261.

taken from THE MANUFACTURE OF CHEMICAL S BY ELECTROLYSIS (sciencemadness library)

That's pretty interesting. The reference doesn't give any details on how to go about superimposing the AC over the DC though. Things such as voltage and current density, frequency etc are probably important here. I'm definitely going to look into this further. Has anyone else ever heard of this, or tried it?




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[*] posted on 25-4-2012 at 19:44


when disstilling benzaldehyde at atmospheric presure, approximately how much of it will be lost a it turns to benzoic acid?



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[*] posted on 11-5-2012 at 18:31


Were I to attempt to make benzaldehyde, I would do this:

Toluene ------> benzyl bromide

This is a free radical halogenation obviously, keep an excess of toluene to minimise formation of di and trisubstituted toluene, you can always recover this and re-use it. No, you don't need a UV light source (though it would help), just keep it refluxing with a bright light source if possible until the red colour from the bromine disappears.

benzyl bromide -----> benzaldehyde

Treat the benzyl bromide with stoichometric (slight excess would be better) amounts of DMSO (dimethyl sulphoxide) and a stoichometric amount of weak base (slight excess would be better) of your choice (sodium carbonate should work just fine) in a high boiling point solvent at reflux (using toluene would make this a one pot synthesis). This reaction will release dimethyl sulphide as a by product, so make sure you do this outside and wash your glass with bleach. This is a Kornblum oxidation, for those of you who are interested. Yields are reported to be around 70% so this 2 step method should be a viable method of benzaldehyde production.

Please let me know how this goes if anyone decides to try it, free radical halogenations with bromine aren't actually as user unfriendly as with chlorine, so don't let that put you off.

[Edited on 12-5-2012 by SteveJones]
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[*] posted on 29-5-2012 at 10:23


I decided to break out the ol' manganous-ammonium alum the other day, and oxidized some toluene, just for the hell of it. The stuff had been sitting in a sealed ptfe bucket for probably two years, maybe more. I had completely regenerated the oxidizer before I stored it, and it looked exactly the same two years later as the day I stored it.
I'm still not sure why more people don't use this method, since its so easy. From about 1 gallon of 60% acid, saturated with the deep purple alum, (just a small bit of undesolved solids) and around 700ml of toluene (I like to use a big excess, for various reasons) around 325ml of distilled aldehyde was obtained in around 3 hours.
Those who can't make this work, simply aren't doing it right. It's that simple.
When it comes to chemistry, if I can make it work, them damn near anyone should be able to make it work.

http://www.sciencemadness.org/talk/viewthread.php?tid=6882





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[*] posted on 26-6-2012 at 03:02


i am hoping you can tell me, is manganese sulphate (monohydrate) used in the benzyldehyde electro reaction? or is it the tetra/pentahydrate?
and if it is the tetrahydrate, how do i convert the monohydrate to that? can i just add water? i dont realy understand the meaning of a hydrate. it seems to mean 100 differnet things depending on context. if someone could explain it i would be grateful.

also can you link me to the method of purifying benzldehyde using ammonia persulphate? i realy dont understand the process.

thankyou alot
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[*] posted on 29-6-2012 at 20:41


Quote:
i am hoping you can tell me, is manganese sulphate (monohydrate) used in the benzyldehyde electro reaction? or is it the tetra/pentahydrate?
and if it is the tetrahydrate, how do i convert the monohydrate to that? can i just add water? i dont realy understand the meaning of a hydrate. it seems to mean 100 differnet things depending on context. if someone could explain it i would be grateful.

also can you link me to the method of purifying benzldehyde using ammonia persulphate? i realy dont understand the process.

thankyou alot

Most of the MnSO4 you would get through the usual channels will be the monohydrate.

Ammonium persulfate isn't used in this process. It would oxidize benzaldehyde, so Im pretty sure it wouldnt be used in any purification process either.

http://en.wikipedia.org/wiki/Manganese%28II%29_sulfate




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[*] posted on 3-7-2012 at 05:51


@ hilski you didnt answer my question at all! my question is what was used in the reaction, not what you can and cant get. and your right. my mistake, i think i meant sodium bisulphite, the chemical that has been mentioned a few times in the purification of benzyldehyde or was it a differnet chemical?
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[*] posted on 9-7-2012 at 09:48


Quote:
@ hilski you didnt answer my question at all! my question is what was used in the reaction, not what you can and cant get

Really?
Quote:
Most of the MnSO4 you would get through the usual channels will be the monohydrate.

If I'd used anything different, I would have said so.

And yes, bisulfite can be used for purification via the addition product, hydrolysis with Na2CO3 solution, followed by steam distillation etc. etc.

Washing the toluene/aldehyde with water and Na2CO3 solution before vac distillation is enough. It's not really necessary to go through the extra purification steps in my opinion.




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[*] posted on 13-7-2012 at 22:48


sorry if this has already been mentioned, but i am not going through 20 pages of posts.

can you oxidise toluene with TCCA in water, instead of using all this valuable H2SO4.

proposed equations:

(CNO-Cl)3 + 3H2O ===> (CNO-H)3 + 3HOCl

2HOCl + C6H5CH3 ===> 2HCl + C6H5CHO + H2O

sorry for no references, i cant find the pdf, but i believe it is called something like "TCCA- a safe and efficient oxidant"

it showed many examples of oxidations in presence of water with TCCA




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[*] posted on 14-7-2012 at 10:56


You might find it in here: http://www.sciencemadness.org/talk/viewthread.php?tid=9336
and here:
http://www.sciencemadness.org/talk/viewthread.php?tid=1751



[Edited on 14-7-2012 by madcedar]
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[*] posted on 15-7-2012 at 12:38


Quote:
can you oxidise toluene with TCCA in water, instead of using all this valuable H2SO4.

No.

But TCCA can be used for producing benzylchloride from toluene.
https://www.sciencemadness.org/whisper/viewthread.php?tid=14...




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[*] posted on 28-9-2012 at 18:51
Gas Mask


Quote: Originally posted by Hilski  
Quote:
can you oxidise toluene with TCCA in water, instead of using all this valuable H2SO4.

No.

But TCCA can be used for producing benzylchloride from toluene.
https://www.sciencemadness.org/whisper/viewthread.php?tid=14...


I have done the TCCA with toluene and it is a serious vapor
problem and quite annoying. I am now trying the electrolytic
method even with my 300 cfm vent hood it poses a problem.:cool:
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[*] posted on 26-11-2012 at 15:54


Is it possible to oxidize benzyl alcohol vapor with silver catalyst into benzaldehyde?
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[*] posted on 10-12-2012 at 01:34


Quote: Originally posted by chucknorris  
Is it possible to oxidize benzyl alcohol vapor with silver catalyst into benzaldehyde?


I would recommend using dilute nitric acid [1] instead. It is much easier then working with vapour...

===
[1] Joshi, S., & Kataria, K. (2005). Kinetics of Oxidation of Benzyl Alcohol with Dilute Nitric Acid. Industrial & engineering …, 325–333.
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[*] posted on 10-1-2013 at 12:04


As previosuly mentioned, toluene can be converted into benzaldehyde using MnO2. See for instance

http://www.google.com/patents/US613460

Reaction of toluene and MnO2 in ~60% sulphuric acid --> benzaldehyde.

Question : where does the O come from - what happens to the MnO2?
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[*] posted on 11-1-2013 at 20:26


2MnO2 + 4H+ + PhCH3 -> PhCHO + 2Mn+2 + 3H2O

2MnO2 + 2H2SO4 + PhCH3 --> PhCHO + 2MnSO4 + 3H2O
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[*] posted on 24-1-2013 at 19:18


Quote: Originally posted by MeSynth  
100 mls., of aqueous phase, containing ferric sulphate (pFe=2), hydrogen peroxide (concentration 0.135 molar), and containing 1 gram. equivalent per liter of the acid stated in Table 4 below, were vigerously stirred with 100 mls. of toluene at 85C for 3 hours. Table 4 gives yield of benzaldehyde.

Nitric acid 74.5% yield
Hydrochloric acid 58.5% yield (what the?)
Sulfuric acid 55% yield

----------------------------------------Taken from US3531519

My main question is how much ferric sulphate is used? I do not comprehend (pFe=2) ?

If someone could help me figure out pFe=2 I would be greatful.


There is a pFe calculation in this file.


Attachment: 2008 test2key.pdf (53kB)
This file has been downloaded 1602 times
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[*] posted on 8-3-2013 at 23:40


I finnally got 1kg of manganese sulphate and can use it to oxidize toluene to benzaldehyde (electrolysis of MnSO4, H2SO4, (NH4)2SO4 )

What I'd like to know, if anyone can help me is a mechanism for the reaction, because I can't really imagine the methyl group to react so readily, being quite unreactive... The problem is that I don't have pure toluene and will have to get it from a paint thinner (40% toluene, 10% alkanes-C6-C11, the rest is acetone). The alkanes are almost impossible to remove from toluene and I've been wondering if they're gonna be oxidized as well? I really doubt that since they're very unreactive generally but if toluene is oxidized by the reagent perhaps so could be the alkanes?
I know the question is a bit silly but I'd like to be sure everything goes smoothly :)

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