Sciencemadness Discussion Board

Chlorobenzene from Benzoic Acid?

krfkeith - 24-5-2013 at 01:30

So I've been looking for ways to get to chlorobenzene without first making benzene and then chlorinating it. Benzoic acid is fairly easy to come by, and not nearly as scary as benzene proper.

Now supposedly, benzoic acid can be chlorinated by an aqueous solution of sodium hypochlorite, so bleach. Obviously, since we're trying to make chlorobenzene, the ortho, meta, or para isomer shouldn't matter. Upon further research, I found that benzoic acid can apparently be reacted with calcium oxide to make benzene. So, would this reaction also work with chlorinated benzoic acid?

To review, what I'm trying to do is:

C6H5COOH + NaClO (aq) --> C6H5COOHCl + Na2O

C6H5COOHCl + CaO --> C6H5Cl + CaCO3 (?)

Am I totally off base here? On the right track?

Any help is greatly appreciated! Thanks!

[Edited on 24-5-2013 by krfkeith]

[Edited on 24-5-2013 by krfkeith]

ParadoxChem126 - 24-5-2013 at 08:10

Here is one way to make chlorobenzene from benzoic acid:

React the benzoic acid with methanol and an acid catalyst to make methyl benzoate. Then react the methyl benzoate with ammonia to make benzamide. Use bleach and sodium hydroxide to do a Hoffman degredation on the benzamide, forming aniline. React the aniline with nitrous acid (sodium nitrite + sulfuric acid) to form the benzenediazonium ion. Now react the benzenediazonium with copper chloride to make chlorobenzene.

Technically, benzoyl chloride works better than methyl benzoate, but the thionyl chloride needed to make it from benzoic acid is harder to find than methanol.

vmelkon - 24-5-2013 at 09:47

Quote: Originally posted by krfkeith  

C6H5COOH + NaClO (aq) --> C6H5COOHCl + Na2O

[Edited on 24-5-2013 by krfkeith]

[Edited on 24-5-2013 by krfkeith]


Your product doesn't make any sense
C6H5COOHCl
(The chlorine is binding to what atom?)

and also the equation isn't balanced and also you aren't going to get sodium oxide in a aqueuas solution, you get sodium hydroxide instead.

Boffis - 24-5-2013 at 12:51

A paper was posted on another thread about decarboxylation of various benzoic acids including p and m chlorobenzoic acids and they were found to be fairly resistant to decarboxylation. So while it may be possible it may require very aggressive condition such as calcining the Na salt but as discussed elsewhere on this forum the production of benzene via this route is not simple and the presence of an extra chlorine increases the risk of side reactions. Indeed in the paper attached two of the acids generated unidentified carbonyl (benzophenone derivative?) compounds.

So Paradoxchem's suggestion looks like a better route even if much more complex. It may be possible to simplify it using boric acid catalysed amide formation without going through the acid chloride or the ester. Incidently both analine salts and chlorobenzene crop up on ebay from time to time, have you had a look recently?

Attachment: Decarboxylation of benzoic acid derivatives & synthesis of Cheng-Hsai Wang.pdf (1.3MB)
This file has been downloaded 1195 times

bbartlog - 24-5-2013 at 13:07

The conditions in the above-referenced paper are pretty mild for this reaction... DSMO boils at 189C. So I wouldn't give up on the decarboxylation just because it didn't work there.
And paradoxchem's suggestion is ludicrous; 8 or 9 chemicals (not counting solvents you might need at various points) and five steps to get to a relatively simple compound? Proceeding via benzene would be better than that.

S.C. Wack - 24-5-2013 at 16:07

I've posted that aniline can be made by the Schmidt reaction or nitromethane and polyphosphoric acid. But if benzene is bad then NaN3 and CH3NO2 (and aniline) probably are too, and not particularly cost effective.

So good luck with that. Might want to follow beaten paths.

krfkeith - 24-5-2013 at 16:53

I think that I'm just going to go ahead and go through benzene. It isn't that bad after all, as long as you're not stupid.

ParadoxChem126 - 24-5-2013 at 17:03

Quote: Originally posted by bbartlog  

And paradoxchem's suggestion is ludicrous; 8 or 9 chemicals (not counting solvents you might need at various points) and five steps to get to a relatively simple compound? Proceeding via benzene would be better than that.

I was trying to give a way to make chlorobenzene without making benzene first, like the author wanted. Also, the author probably wanted to explore organic chemistry, and my method explored many reactions. Also, the chemicals needed in my method are relatively easy to obtain.

krfkeith - 24-5-2013 at 17:26

Paradoxchem, I appreciated your reply! Thansk!

I had another idea though, what about demethylation of chlorotoluene?

Random - 26-6-2013 at 14:10

Quote: Originally posted by S.C. Wack  
I've posted that aniline can be made by the Schmidt reaction or nitromethane and polyphosphoric acid. But if benzene is bad then NaN3 and CH3NO2 (and aniline) probably are too, and not particularly cost effective.

So good luck with that. Might want to follow beaten paths.


Aniline out of nitromethane? Could you elaborate?

ParadoxChem126 - 6-7-2013 at 13:59

Quote: Originally posted by krfkeith  
I had another idea though, what about demethylation of chlorotoluene?


How do you plan to do that?

halogen - 6-7-2013 at 18:44

http://onlinelibrary.wiley.com/doi/10.1002/chin.200533074/ab...

chlorodecarboxylation, I remember thinking 'you can do that?'

bbartlog - 8-7-2013 at 06:20

This is a variant of the Kochi reaction which is itself considered a variation of the Hunsdiecker decarboxylation.

clearly_not_atara - 18-5-2022 at 08:37

I'm a little surprised that the simple method didn't get more attention, here. Chlorination of sodium benzoate by sodium hypochlorite in aqueous solution is about as easy as it gets. I can't imagine chlorinating benzene, which is not water-soluble, with chlorine, a gas, could possibly be easier, particularly since you then need Lewis acids. The negative charge on benzoate activates it towards chlorination. See e.g.:
https://www.nature.com/articles/131028d0

Wang's paper attached above by Boffis is a method specifically tuned to the electron-deficient carboxylic acids. Indeed, the various toluic acids gave no yield in this method, while 3-nitrophthalic acid gives a product. Meta-chlorobenzoic acid is not really that electron-deficient, so it is not surprising that the decarboxylation doesn't take. However, p-chlorobenzoic acid and o-chorobenzoic acid are successfully decarboxylated by heating in resorcinol:
https://www.journal.csj.jp/doi/pdf/10.1246/bcsj.33.1154

m-chlorobenzoic acid was successfully decarboxylated in high yield by the "standard" method of heating with CuCO3 in quinoline to 250 C, while 2,4-dichlorobenzoic acid required the use of the stronger catalyst Ag2CO3:
https://pubs.acs.org/doi/pdf/10.1021/ac60032a017

Furthermore, a YouTube video I don't feel like watching claims the decarboxylation of sodium chlorobenzoates by simple heating:
https://www.youtube.com/watch?v=2FgNxFey_2U

In fact, even OP's original goal of avoiding any benzene production can be satisfied with a selective decarboxylation in DMSO at 120 C with catalytic Ag2CO3 (granted expensive / low yield):
https://chemistry-europe.onlinelibrary.wiley.com/doi/pdf/10....

I fail to see how a method involving a Sandmeyer reaction (exothermic, foamy) could possibly be preferred. Since chlorobenzene is safer than chloroform, while having similar properties, I think these methods should not be ignored.

Jenks - 19-5-2022 at 07:12

That's a great suggestion. Dichlorination may be an issue so be careful about the amount of bleach added, limiting it to one molar equivalent of chlorine or slightly over. I like the decarboxylation using copper carbonate - I did not know that was a decarboxylation catalyst - but the solvents proposed in this thread (resorcinol, quinoline) are crazy. Maybe the decarboxylation would work neat, without solvent, carefully controlling the temperature and distilling off the chlorobenzene as it forms, as is done with sodium benzoate -> benzene.

Incidentally, I happened to make copper carbonate recently, as my wife who teaches high school was needing a demo. A pre-1983 penny was mostly dissolved in slightly diluted nitric acid and the copper nitrate was precipitated as the (approximate) copper carbonate using washing soda (sodium carbonate).

DraconicAcid - 19-5-2022 at 15:32

Quote: Originally posted by vmelkon  
Quote: Originally posted by krfkeith  

C6H5COOH + NaClO (aq) --> C6H5COOHCl + Na2O

[Edited on 24-5-2013 by krfkeith]

[Edited on 24-5-2013 by krfkeith]


Your product doesn't make any sense
C6H5COOHCl
(The chlorine is binding to what atom?)

and also the equation isn't balanced and also you aren't going to get sodium oxide in a aqueuas solution, you get sodium hydroxide instead.


Clearly, the OP means C6H5CO2H + OCl- --> ClC6H4CO2- + H2O

SWIM - 19-5-2022 at 19:18

Quote: Originally posted by Jenks  
That's a great suggestion. Dichlorination may be an issue so be careful about the amount of bleach added, limiting it to one molar equivalent of chlorine or slightly over. I like the decarboxylation using copper carbonate - I did not know that was a decarboxylation catalyst - but the solvents proposed in this thread (resorcinol, quinoline) are crazy. Maybe the decarboxylation would work neat, without solvent, carefully controlling the temperature and distilling off the chlorobenzene as it forms, as is done with sodium benzoate -> benzene.


Benzoate to benzene is generally done by dry distilling with soda-lime.
I get the feeling that doing this might be pretty hard on that chloro group. Especially since its a very high temperature reaction.

Might be

clearly_not_atara - 23-5-2022 at 11:38

There is no hydrolysis of the aryl chloride; however, the carbanion intermediate C6H4Cl- can lose chloride to form a benzyne under simple salt pyrolysis:
pubs.acs.org/doi/full/10.1021/jp071241x

So lower-temperature catalytic methods are better.