Sciencemadness Discussion Board
Not logged in [Login ]
Go To Bottom

Printable Version  
Author: Subject: toluene --> benzoic acid...
evil_lurker
National Hazard
****




Posts: 767
Registered: 12-3-2005
Location: United States of Elbonia
Member Is Offline

Mood: On the wagon again.

[*] posted on 13-8-2005 at 06:01
toluene --> benzoic acid...


I'm looking for a good cheap method of turning toluene into benzoic acid in kilogram size quantities.

KMnO4 is basically out of the question due to cost, although it might be used to create some MnO2.

Any suggestions?
View user's profile View All Posts By User
Sergei_Eisenstein
Hazard to Others
***




Posts: 290
Registered: 13-12-2004
Location: Waziristan
Member Is Offline

Mood: training

[*] posted on 13-8-2005 at 06:56


Another route might be the oxidation with Chromium salts, but it might be a problem with the cost as well. If I was asked to synthesize a few kilo of benzoic acid in a cost effective way, I'd try adding solid CO2 to phenylmagnesium bromide.
View user's profile View All Posts By User
budullewraagh
Hazard to Others
***




Posts: 168
Registered: 1-8-2004
Location: new york
Member Is Offline

Mood: Aliphatic

[*] posted on 13-8-2005 at 10:18


direct oxidation with KMnO4 or CrO3 or CrO4-2 salts wouldnt work, as there are no pi electrons connected to the methyl group of toluene. free radicals wouldnt work.

you could try using chlorine radicals to chlorinate the methyl group of toluene, then react with hydroxide to form benzyl alcohol, then oxidize to benzoic acid with chromic acid




Check out my political blog and click lots of ads:
http://www.independent-thinkers.blogspot.com
View user's profile View All Posts By User
Sergei_Eisenstein
Hazard to Others
***




Posts: 290
Registered: 13-12-2004
Location: Waziristan
Member Is Offline

Mood: training

[*] posted on 13-8-2005 at 11:37


Quote:
Originally posted by budullewraagh
direct oxidation with KMnO4 or CrO3 or CrO4-2 salts wouldnt work, as there are no pi electrons connected to the methyl group of toluene. free radicals wouldnt work.




As far as my chemistry knowledges reaches, potassium permanganate and chromic acid are strong enough to oxidize alkyl side chains of an arene. The only condition is that the benzylic carbon has at least one hydrogen, i.e. -CH3, -CH2R and -CHR2 can be oxidized but -CR3 cannot.

I'm pretty sure this works. For instance, p-nitrobenzoic acid is prepared by Na2Cr2O7-oxidation of p-nitrotoluene (nitration of benzoic acid gives the m-isomer), and terephthalic acid (PET precursor) is made in the lab by KMnO4-oxidation of p-xylene (aerobic oxidation in the industry).
View user's profile View All Posts By User
Eclectic
National Hazard
****




Posts: 899
Registered: 14-11-2004
Member Is Offline

Mood: Obsessive

[*] posted on 13-8-2005 at 13:30


There is a lab scale prep for phthalic anhydride from napthaline that involves passing air and naphthaline vapours through a V2O5 catalyst. The same setup would probably work for toluene...
View user's profile View All Posts By User
Sandmeyer
National Hazard
****




Posts: 784
Registered: 9-1-2005
Location: Internet
Member Is Offline

Mood: abbastanza bene

[*] posted on 13-8-2005 at 14:27


Quote:
Originally posted by budullewraagh
direct oxidation with KMnO4 or CrO3 or CrO4-2 salts wouldnt work, as there are no pi electrons connected to the methyl group of toluene. free radicals wouldnt work.


http://www.orgsyn.org/orgsyn/RxnTypes/section.asp?section=18...




View user's profile View All Posts By User
WizardX
Hazard to Self
**




Posts: 61
Registered: 11-8-2005
Location: wizardx.4shared.com
Member Is Offline

Mood: wizardx.suddenlaunch3.com

[*] posted on 13-8-2005 at 17:42


BENZIL http://www.orgsyn.org/orgsyn/prep.asp?prep=cv1p0087

Oxidative cleaverage of Benzil gives 2 moles of Benzoic acid.


CARBOXYLIC ACIDS FROM THE OXIDATION OF TERMINAL ALKENES BY PERMANGANATE
http://www.orgsyn.org/orgsyn/prep.asp?prep=cv7p0397

Styrene ==> Benzoic acid 96%
View user's profile Visit user's homepage View All Posts By User
budullewraagh
Hazard to Others
***




Posts: 168
Registered: 1-8-2004
Location: new york
Member Is Offline

Mood: Aliphatic

[*] posted on 20-8-2005 at 06:17


can somebody show me a mechanism for this oxidation? i can see this working if an alcohol were an intermediate, but it is a stretch to see the initial oxidation occur



Check out my political blog and click lots of ads:
http://www.independent-thinkers.blogspot.com
View user's profile View All Posts By User
evil_lurker
National Hazard
****




Posts: 767
Registered: 12-3-2005
Location: United States of Elbonia
Member Is Offline

Mood: On the wagon again.

[*] posted on 20-8-2005 at 08:25


Actually any oxidation for benzaldehyde would work, its just a matter of pushing it hard enough so that the end product is the acid.
View user's profile View All Posts By User
Eclectic
National Hazard
****




Posts: 899
Registered: 14-11-2004
Member Is Offline

Mood: Obsessive

[*] posted on 20-8-2005 at 08:59


There are some liquid phase toluene oxidations to benzoic acid that just involve bubbling air through toluene in the presence of a transition metal catalyst.
just throw in some copper, manganese,cobalt, and iron acetate. Any or all of the above. I don't think it's too picky. A patent search should turn up details...
View user's profile View All Posts By User
sparkgap
International Hazard
*****




Posts: 1234
Registered: 16-1-2005
Location: not where you think
Member Is Offline

Mood: chaotropic

[*] posted on 20-8-2005 at 11:18


Anyone recall what catalyst(s) are used in air-oxidizing alkylbenzenes to their corresponding acids? May take a while, but most certainly useful in evil_lurker's scenario.

sparky (~_~)




"What's UTFSE? I keep hearing about it, but I can't be arsed to search for the answer..."
View user's profile View All Posts By User
budullewraagh
Hazard to Others
***




Posts: 168
Registered: 1-8-2004
Location: new york
Member Is Offline

Mood: Aliphatic

[*] posted on 21-8-2005 at 05:52


permanganate or chromic acid work well for the oxidation of aldehydes to carboxylic acids. you could try that.

also you could use thionyl chloride to form the acyl halide, then just convert to the acid




Check out my political blog and click lots of ads:
http://www.independent-thinkers.blogspot.com
View user's profile View All Posts By User
evil_lurker
National Hazard
****




Posts: 767
Registered: 12-3-2005
Location: United States of Elbonia
Member Is Offline

Mood: On the wagon again.

[*] posted on 21-8-2005 at 10:02


I tried the KMnO4 oxidation of toluene last night and let me tell ya, toluene is some tough stuff to oxidize!!!

Even after 5 hours of reflux, I still had a toluene layer floating on top of the reaction vessel. I did manage to get a little yield though.

But all things considered, the time and effort in using that synth it is just not worthwhile especially when you can purchase it off the net for less than $10 a pound.

As far as the catalystic air oxidation, I recall seeing something that called for I believe cobalt acetate at 10 atmospheres. Yields were crappy though at 14% total product conversion, but it was meant for producing benzaldehyde. If you could just get it out in the open, hook up a good reflux condensor on it and bubble the crap outta some air thru it for 24 hours, it might actually be worth it.

Anyways, I just stumbled onto something interesting.

http://pubs.acs.org/cgi-bin/abstract.cgi/iecred/2001/40/i26/...

Talks about electrochemically oxidizing toluene using cobalt acetate. Benzyl Acetate would be a useful byproduct, if

If I'm thinking correctly it could be decarboxylated (correct term)? to benzene?





[Edited on 21-8-2005 by evil_lurker]
View user's profile View All Posts By User
mick
Hazard to Others
***




Posts: 338
Registered: 3-10-2003
Member Is Offline

Mood: No Mood

[*] posted on 21-8-2005 at 11:19


Oxidising toluene to benzoic acid would involve
alcohol and aldehyde intermediates which could react with each other so the yields could be low because of dimeric compounds such as ketones, something like benzophenone.
If you can convert to a CN group. H2O2 and NH3 should give you the amide which should give the acid with water

mick
View user's profile View All Posts By User
unionised
International Hazard
*****




Posts: 5123
Registered: 1-11-2003
Location: UK
Member Is Offline

Mood: No Mood

[*] posted on 22-8-2005 at 10:36


Benzopheneone? where did the other carbon go?

Among the compounds that you might get from coupling 2 benzaldehydes together is benzoin. That's easily oxidised to benzil and that in turn (as has been pointed out) gives benzoic acid on oxidation anyway. Losses by coupling this way will be small because many of the products will get cleaved and oxidised to the right product in the end.

If you can turn the methyl group into a CN then you only have to hydrolyse it to get the acid. I wouldn't waste H2O2 or NH3 on it.
View user's profile View All Posts By User

  Go To Top