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Author: Subject: toluene --> benzaldehyde
Mendeleev
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[*] posted on 13-11-2005 at 18:03


Hello forumites, i've been gone for a while but i'm in college now and taking a bunch of interesting chemistry classes and I remembered the good ole forum. Anyway back to benzaldehyde, I found pretty interesting and easy looking procedure for producing benzaldehyde, in Rhodium's archive.

You need benzyl alcohol, DMSO, and aqueous 48% HBr. Now benzyl alcohol isn't exactly toluene, but if you can get that from toluene or just get straight up benzyl alcohol(photo supply). I'm not at my computer so I can't pull up any references at the moment, but the procedure they gave used 550 mg benzyl alcohol in 5 mL DMSO and I think a 3:1 ratio of benzyl alcohol:HBr.

The procedure is pretty straight forward, throw all those reactants in a flask, heat to 100 C for 3 hours, extract with your solvent of choice probaby DCM or ether and distill. The procedure works with substituted benzaldehydes and gives very good yields. The yield they gave from plain benzyl alcohol was 95% or something like 533 mg benzaldehyde from 550 mg benzyl alcohol.

DMSO can be bought OTC, it penetrates skin and whatever you dissolve it will get absorbed into your blood stream so it has veterinary applications(horse liniment) and you could probably find it at petsmart or if not I know for a fact that they have it or used to have it at the tractor supply co. HBr from H2SO4 and pool brominating tablets.

I'll post more details and references next time I pull up the file.

[Edited on 14-11-2005 by Mendeleev]




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[*] posted on 14-11-2005 at 03:24


I just had an idea... why not use bromine instead of chlorine in a photo-cataylized halogenation of toluene?

Bromine is liquid at room temps... brominating toluene would be as simple as pouring it in a flask along with some toluene in the correct proportions, setting the flask out in the sun and turning on the magnetic stirrer.

If one wanted, they could then pump in chlorine gas in the dark, which should displace the bromine and form benzyl/benzal chloride.

The bromine could be caught in water and recycled for later use.
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Mendeleev
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[*] posted on 15-11-2005 at 10:05


That could probably work but you would probably need some sort of catalyst because the bromine radical isn't as reactive as the chlorine radical.



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[*] posted on 15-11-2005 at 10:18


An advantage of bromine is that benzotribromide cannot be formed. So you get nearly quantitative yields of benzal bromide when using a stochiometric amount of bromine (don't forget that half of the bromine is evolved as HBr!).
C6H5-CH3 + 2 Br2 -----> C6H5-CHBr2 + 2 HBr
No special initiators are needed, just slowly add the bromine to refluxing toluene irradiated with bright light.

The disadvantage of bromine is that formation of ringbrominated derivatives is promoted, because the reaction will take longer and cannot be made as hot as the reaction with chlorine (think about the boiling point of bromine).
So the produced benzaldehyde would have to be fractionated thoroughly in order to seperate bromobenzaldehyde.
It is also crucial that the toluene be distilled before use! Any iron contamination will totally screw up the reaction.

For industry, bromine is too expensive, so only methods using chlorine have been used.

But in the laboratory, bromine has the very important advantage of convenience.
All the reagents are liquid, and can be mixed in every desired proportions.
The ringbrominated byproducts can be seperated by fractional distillation, this step would be needed with chlorine too because of the formation of benzotrichloride.

In the lab, bromine is the better choice.

[Edited on 15-11-2005 by garage chemist]
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S.C. Wack
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[*] posted on 15-11-2005 at 12:06


There are of course a jillion ways to do things...they all have some disadvantage or other...even in the dark
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S.C. Wack
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[*] posted on 23-11-2005 at 19:55


I've finally gotten around to photocopying the 100 year old French Rec. trav. articles mentioned in the above JACS article, just because I can. In the unlikely event that anyone else wants to see them...

http://rapidshare.de/files/8073921/bz_br.pdf.html
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[*] posted on 23-11-2005 at 20:45


SC Wack, don't be discouraged, don't be frustrated. Your efforts are truly noted (and I am not just speaking for myself).
You don't have the 'bibliomaster' title for no reason'. :P
Although this may be in French, I'll always know, if I am ever to run into difficulties of making benzaldehyde from toluene (via bromination), the article you scanned will be one to check; presumably the same for many others here.
Although of course I'd first produce it from benzoylalcohol and K2Cr2O7 :)
Seriously, keep up the good work. Not everyone may appreciate/need it, but still, it doesn't mean it's a waste of time.
The sheer broadness of this forum is what I like about it. Any language, any noteworthy procedure is worth diamonds as long as it works, regardless the language or intention.

Furthermore, I am sure some people are willing to translate if that is required.

Many thanks, and regards.




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[*] posted on 17-2-2006 at 11:31


Aromatic Aldehydes Via Catalytic Oxidation
R.A. Sheldon, N. de Heij, Andeno B.V.
Summary: The various methods for the oxidation of substituted toluenes to the corresponding benzaldehydes, e.g. autoxidation, catalytic oxygen transfer, electro(catalytic) oxidation and oxidative bromination, are reviewed and evaluated. The cobalt catalyzed autoxidation of para-cresol, in methanolic sodium hydroxide solution at 60°C, is discussed in detail. Under optimal conditions para-hydroxybenzaldehyde is obtained in ca. 90% selectivity at 95% para-cresol conversion.

From: W. Ando and Y. Moro-oka (Eds),
The Role of Oxygen in Chemistry and Biochemistry, Proceedings of an International Symposium on Activation of Dioxygen and Homogeneous Catalytic Oxidations, Tsukuba, Japan, 12-16 July 1987 Studies in Organic Chemistry, Volume 33, pp. 243-256, 1988

Attachment: oxidn.Ar-CH3.to.Ar-CHO_Studies.in.Org.Chem.33,243-56(1988).djvu (88kB)
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[*] posted on 21-2-2006 at 17:08


While browsing for a journal request for Sandmeyer I found this:

Unusual reactivity of peroxo vanadium complex for catalytic oxidation of aralkenes to benzaldehydes selectively (>99%) in conjunction with aqueous H2O2 as an oxidant is described here for the first time.

Don't know if it's been up before.

[Edited on 22-2-2006 by Phel]

Attachment: Peroxo_vanadium_cat_for_sel_ox_of_aralkenes_to_BzCHO.pdf (162kB)
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[*] posted on 1-3-2006 at 21:28
styrene -> benzaldehyde


You could always start with styrene and use ozonolysis or just treatment with acidic KMnO4.
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[*] posted on 8-3-2006 at 20:18


Toluene Trouble


After reading CycloKnights success using the patent 808095/UF method, swim was all fired up with enthusiasm. Swim developed a setup on a slightly less than 1/4 scale of the original patent. The power supply was homemade & delivered ~60 amps. A washing machine motor was used via pulleys to drive a stirer.

Charging the solution worked well & the color turned from a whitish yellow to a very dark red.

On adding the toluene (excess was used) it took 24 + hrs for the solution to loose color. The product was extracted & turned out to be mostly benzoic acid.

Later swim made more oxidant & tried again copying CycloKnights volumein a beaker. There was no benz smell at least for 1/2 an hr & then it was only faint. After 2 hrs swim gave up.

After procurring a small quantity of benzyl alcohol (20 ml), on addition to 200ml of oxidant the smell of benz was almost immediate. So obviously the oxidant is ok.

All inputs used were tech grade including the toluene which according to the supplier was 98.6% pure. Could it be that the toluene in oz is contaminated, perhaps the other 1.4% is thiotolenes or thiophenes & inhibiting the oxidation process.

Swim would be grateful for any help.
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[*] posted on 9-3-2006 at 04:41


You really need to give more details on the reaction parameters such as electrode material, current density, temperature, faradays passed and etc.

PhCOOH being a two oxygen reaction versus the aldehyde
being only one it seems that somehow you overoxidized the substrate.

Also always a very wise thing to do when doing a new (to you) reaction is using a small scaled say 250ml beaker with everything proportional to the 72 liter tank you will eventually use. Saves a lot of headaches and wastes
few chemicals when something goes wrong. Remember
Murphy's First Law?
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[*] posted on 13-3-2006 at 22:12


You are certainly right there bio2. Murphy is always lurking around the corner.

Swim followed the patent (808095) in most areas, an outer anode & an inner cathode plus a central stirer. The temp used was 50 C +/- 3. The oxidant was charged with 6000/4.3 amp hrs i.e. 62 amps for 22 1/2 hrs. Anode & cathode were copperised lead sheet which is used for flashing in building construction, with the cathode being full of holes drilled out with a hole saw as against using rods, for more stability when stiring. current density at the anode was ~2.5 amps per sq. decimeter.

The original patent says the reaction was complete after 2 to 3 hrs. Regards CycloKnight, one he did took about an hour.

Its as though the oxidant is able to convert the benz to benzoic acid easier than from toluene to benz.
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[*] posted on 21-3-2006 at 17:50


I don't know if this was discussed in this thread or not, but
What about turning aniline to benzaldehyde?

http://www.orgsyn.org/orgsyn/prep.asp?prep=cv5p0139

The anline can be synthesized, formaldehyde can be bought, along with hydroxylamine




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[*] posted on 9-4-2006 at 20:51


More alkane oxidations, mostly Mn, just for hahas.

Without electricity-
http://v3.espacenet.com/origdoc?DB=EPODOC&IDX=GB1206268&...

With (illustrated for anisaldehyde, but a bit different, so)-
http://v3.espacenet.com/origdoc?DB=EPODOC&IDX=US3985809&...
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[*] posted on 15-4-2006 at 07:34


Nice syntheses on orgsyn.org.

I think benzahdehyde can be prepared by many ways.

phenylcarbinol (benzyl alcohol)
--->
bezaldehyde

chlorination of toluene to benzalchloride
C6H5CHCl2
--->
bezaldehyde

or maybe chloromethanol is prepared by methanol and HCl ;)
and the chloromethanol is threathed with Clorox bleach and NaOH solution to bezaldehyde.

[Edited on 15-4-2006 by Madandcrazy]
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[*] posted on 20-4-2006 at 22:14


Could it be that the toluene in oz is contaminated.

Have had many reports of a residue in evaperation dishes in labgrade and service station sources.




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[*] posted on 25-4-2006 at 04:04


Quote:
Originally posted by Madandcrazy
Nice syntheses on orgsyn.org.

I think benzahdehyde can be prepared by many ways.

phenylcarbinol (benzyl alcohol)
--->
bezaldehyde

chlorination of toluene to benzalchloride
C6H5CHCl2
--->
bezaldehyde

or maybe chloromethanol is prepared by methanol and HCl ;)
and the chloromethanol is threathed with Clorox bleach and NaOH solution to bezaldehyde.

[Edited on 15-4-2006 by Madandcrazy]


How hard to prepare CH3Cl ? And I looked at chloromethane msds... It's EVIL ! Look :

Stability
Stable. May react violently or explosively with interhalogens, magnesium, zinc, potassium, sodium or their alloys. Incompatible with natural rubber and neoprene composites, but does not attack PVA. Highly flammable. May decompose upon exposure to moist air or water. (So ... HCl must be dried)

Toxicology
Toxic by inhalation - gas is readily absorbed, but very slowly removed from the body. Irritant. Mutagen. Possible carcinogen. Human mutagenic data. May cause systemic effects. Possible teratogen. Gas can be absorbed through the skin.
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[*] posted on 2-5-2006 at 00:40


Quote:
Originally posted by groaner
You are certainly right there bio2. Murphy is always lurking around the corner.

Swim followed the patent (808095) in most areas, an outer anode & an inner cathode plus a central stirer. The temp used was 50 C +/- 3. The oxidant was charged with 6000/4.3 amp hrs i.e. 62 amps for 22 1/2 hrs. Anode & cathode were copperised lead sheet which is used for flashing in building construction, with the cathode being full of holes drilled out with a hole saw as against using rods, for more stability when stiring. current density at the anode was ~2.5 amps per sq. decimeter.

The original patent says the reaction was complete after 2 to 3 hrs. Regards CycloKnight, one he did took about an hour.

Its as though the oxidant is able to convert the benz to benzoic acid easier than from toluene to benz.


It might be worth having a closer look at the exact acid concentration you are using. If there is much deviation from the stated values, then it could easily have a dramatic effect on the aldehyde yield, with benzoic acid being the main side-product. I ended up producing large quantities of benzoic acid before I realised that I simply needed to adjust the acid concentration for much better results.




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[*] posted on 6-6-2006 at 01:54
Any other Route


May be an Stupid Question?
Can I make it using Benzene & some aldehyde or ....May be any other route leaving Toluene.

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[*] posted on 6-6-2006 at 11:47
Cinnamon oil to benzaldehyde update.


Hi peeps, been off the forum a good while but its good to be back :).

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.
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[*] posted on 3-7-2006 at 22:43


Why are you guys making so much dust around benzaldehyde ? The general rule in chemistry synthesis is to BUY everything you can. You will loose a lot of money, time and patience in order to prepare stupid benzaldehyde. In Croatia it is very cheap: 30$ per litre, p.a. purity.

Best regards,
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[*] posted on 3-7-2006 at 22:57


Depending on where your at its not as simple as being able to call up a chemical company and have them send it to your doorstep.

In the USA and several other countries it is considered a controlled substance because of its potential use as a drug precursor... phenylpropylamine, amphetamine, methamphetamine, and ephedrine can all be synthesized with benzaldehyde as one of the precursors.

Attempting to purchase it in the USA will result in law enforcement kicking your door down and searching your premises, and if they don't like what they find you can be arrested and sent to jail for a very long time.
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[*] posted on 4-7-2006 at 01:00


That proves that Croatians have more sense than Americans! Besides, benzaldehyde, which is the principal constituent of artificial almond essence, has a perfectly legitimate use as almond food flavoring, being often used in the sugar "icing" on cakes.
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[*] posted on 22-7-2006 at 22:41


John, is benzaldehyde still legal in NZ? For long? In Queensland and WA its now on the same schedule together with such notables as lysergic acid and P2P. That is 15 years maximum for illegal possession of more than 0.1g! Presumably amateur experimentation is included. The list also includes such obviously drug related chemicals as chromic acid, alkali metals, and magnesium. Here were only allowed to dig ore, and you to tend sheep;)

[Edited on 23-7-2006 by len]

[Edited on 23-7-2006 by len]
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