Sciencemadness Discussion Board

Benzoyl chloride from benzyl alcohol and chlorine

garage chemist - 11-9-2007 at 11:22

While looking for something else I came across the interesting notion in Ullmann that chlorinating benzyl alcohol gives benzoyl chloride (the chloride of benzoic acid, NOT benzyl chloride).
The reference given is GB310909:

The reaction that happens is:
C6H5CH2OH + 2Cl2 ---> C6H5COCl + 3HCl

I thought this might be worth sharing.

Benzoyl chloride is a highly useful substance due to its action as a chlorinating agent towards short-chain carboxylic acids like acetic acid: when glacial acetic acid is mixed with benzoyl chloride, acetyl chloride can be distilled out of the mixture since benzoyl chloride and acetic acid are in equilibrium with benzoic acid and acetyl chloride.

Acetyl chloride is the lowest boiling of those compounds and the equilibrium can therefore be shifted towards the product side by distilling it out.

Benzyl alcohol is available to anyone from e.g. ebay where it is offered frequently. It is also available from pharmacies since it is used a lot in lotions and cosmetic products. It is neither watched nor subject to any government control.

Benzyl alcohol is also useful as a precursor for benzaldehyde and for benzyl chloride (it esterifies readily with concentrated aqueous HCl as outlined in Rhodiums set of benzyl chloride preparations).

[Edited on 11-9-2007 by garage chemist]

trilobite - 11-9-2007 at 15:43

Basically the reaction is oxidation of benzyl alcohol to benzaldehyde and chlorination of benzaldehyde to benzoyl chloride in one pot. There is an example of the latter reaction in Org. Syn.:

I think I have somewhere the old Wöhler and Liebig reference from Org.Syn.

Sauron - 11-9-2007 at 15:53

IIRC benzyl alcohol and benzoyl chloride are quite similar in cost. You mentioned that benzyl alcohol is not regulated, is benzoyl chloride? (I have a consignment of benzoyl chloride, benzotrichloride, and some other goodies sitting at my suppliers' office awaiting delivery to me locally, from Acros. Along with some nitromethane and the long awaited vinyl acetate monomer.)

[Benzoyl chloride $30 a liter

Benzyl alcohol $52 a liter !!

These prices will narrow a bit on a mass basis.

It does not pay to chlorinate benzyl alcohol - unless you can't buy benzoyl chloride where you are.

Wöhler and Liebig, Ann. 3, 262 (1832).

[Edited on 12-9-2007 by Sauron]

trilobite - 11-9-2007 at 16:45

Thank you for your assistance with reading chem supplier catalogs, but the prices are meaningless for those in pursuit OTC reagents. I for one am very aware of the fact that this reaction in particular has lost it's commercial advantage decades ago if there ever was one.

I'm pretty confident that anyone willing to order chemicals they need are perfectly capable of reading the catalogs themselves and making up their mind about which choice suits their needs best. Now, please let us discuss chemistry instead, because that is what this board is all about.

[Edited on 9/12/2007 by trilobite]

not_important - 11-9-2007 at 17:33

Fleaker has a good point. Benzyl alcohol is OTC or nearly so, while the various halides as a minimum have hazmat shipping restrictions, such materials will often not be sold to individuals regardless of any governmental restrictions on sale and possession of the substances.

While the chlorine consumption is high, it doesn't look to be too bad a method when you need a 100 ml or so.

Sauron - 11-9-2007 at 20:04

Oh, sorry, I keep forgetting how many of us are slaves to the Great God OTC.

And how nice for you that you don't give a damn what something costs even when there are several cheaper methods available.

There ARE things that I can't buy off the shelf, and must go the long way round to prepare myself, and yes in that case, cost is of little consequence. Fortunately, for me, benzoyl chloride is not one of them.

Is benzoic acid a problem to purchase? Because TCT chlorinates that very nicely. Yes I know, hard to buy in EU as an individual, but not so hard to buy AFAIK in USA and no problem whatsoever to buy here. A LOT more convenient than setting up a Cl2 generator and a drying train.

trilobite - 12-9-2007 at 01:53

While some see OTC as slavery, others might see it as freedom and some might even find it a challenge. But I do not regard my point of view as the only correct one. I'm simply saying that discussing buying chemicals and their prices instead of chemistry itself would be awfully boring and belongs as a topic to reagents and apparatus acquisition forum, not here.

Benzoic acid is easy to find, of course, but cyanuric chloride (TCT) is indeed different. Typically substances that release HCl gas in contact with water or moisture are a bit hard to find outside chem supplier catalogs.

Sauron - 12-9-2007 at 03:08

Ever heard of VWR? They are a major distributor of apparatus and and reagents in USA and for that matter Canada I believe. They distrubute among others Acros which is part of Thermo Fisher and of course Fisher. Among many other lines. Unlike many suppliers they DO sell to individuals and not just companies or institutional purchasers. So, the situation is nowhere near as dire for north american buyers as all that. I am confident that, quite apart from the ripoff repack operations like sciencelab that I would never recommend, there are probably others besides VWR who will still deal with individuals. I am not in the US or Canada and haven't been for two decades but, it is simply untrue to say that individuals cannot purchase what they need.

It is apparent that some people balk at hazmat fees, but for a decent sized order rather than nickles and dimes, these are not prohibitive. So those people are in fact making a dollars and cents argument just as much as I did - are they not?

There may be people who simply refuse to leave a paper trail and some of those people may even be legitimate. Others are doubless not so legitimate. The latter I have no sympathy for and make no allowances for. The former, well, really ought to do something about those delusions of persecution.

I have nothing again garage chemist's observation of this prep of benzoyl chloride. We both share a respect for this reagent. And in a jurisdiction where benzoyl chloride can't be purchased, any means to make it is a good means. Still, some might be better than others.

It does seem to me that benzaldehyde for many of us is more useful and more desirable than benzoyl chloride, so using benzaldehyde or something from which benzaldehyde can be readily prepared like benzyl alcohol to make benzoyl chloride instead, is an odd allocation of resources.

But it is always nice to have a multiplicity of choices and options.

trilobite - 12-9-2007 at 07:37

The first step in the chlorination of benzyl alcohol is formation of benzyl hypochlorite, Ph-CH2-OCl. Primary and secondary alkyl hypochlorites are unstable and prone to decomposition, with elimination of HCl and formation of the carbonyl compound. I remember reading an article on alkyl hypochlorites where they said that such hypochlorites tended to decompose with loud noises. I believe that benzyl hypochlorite should be most unstable, and to prevent it from accumulating in the reaction mixture one should make sure that the reaction is performed at a temperature high enough. Also some benzyl chloride could form under the conditions of the patent, by reaction between benzyl alcohol and hydrogen chloride, but I don't know what should become of it.

Sauron: For your information I do not live on the american continent. Again your post is off topic and offers no contribution.

garage chemist - 12-9-2007 at 09:04

This was not meant to be an economically sound preparation of benzoyl chloride, but rather a different and unusual preparation of an acyl chloride using easily accessible reagents.
It is meant for those who cant buy benzoyl chloride, not because of jurisdiction but because of lack of sources.

Also, it is meant to show that acyl chlorides do not always have to come from phosphorus chlorides or thionyl chloride as some people seem to believe.

Sauron - 12-9-2007 at 09:22

@trilobite, I am sure I do not give a toss where you reside. You put your trust in patents, do you? Then you are riding for a fall, for sure. You'd bo better to waltz on quicksand.

@gc, Accepted, and perfectly straightforward. No problem.

Nicodem - 12-9-2007 at 09:26

GC, benzoyl chloride can be prepared from benzaldehyde by oxidation with trichloroisocyanuric acid. See patent FR2633616. You can substitute the CCl4 used as solvent with CH2Cl2. Note also that all reagents and solvent must be as dry as possible.
Benzaldehyde can be obtained by oxidizing benzyl alcohol with numerous oxidants including trichloroisocyanuric acid (TCCA). However, this does not necessarily mean you can combine both steps in a one pot procedure since the oxidation of BnOH with TCCA forms an equivalent of HCl which would atack both BnOH (forming BnCl and H2O) and TCCA (forming Cl2 and cyanuric acid). This could make for a complete mess of different products, but you can still try and see what you get...

Sauron - 12-9-2007 at 09:47

Now there's a procedure using two OTC reagents (TCCA being swimming pool chlorinator) and which is adaptable to two different and useful products. Beats the hell out of a chlorine generator.

But patents still make me skittish unless there's peer reviewed lit to support.

Cinnamoyl chloride from cinnamaldehyde

Bromide - 12-9-2007 at 13:59

Thanks for that reference, GC. That seems a useful and straightforward method for amateurs (such as myself) to make benzoyl chloride.

Locally, while TCCA is indeed abundantly available at the nearest Wal-Mart, benzaldehyde on the other hand is not so readily obtained by hobbyists because of legal restrictions. For that reason, and because cinnamaldehyde from cinnamon oil is cheap and plentiful from natural food stores here, I may attempt a similar procedure as in the article, but substituting cinnamaldehyde for benzaldehyde, with the goal of producing cinnamoyl chloride.

If the experiment succeeds, I'm not really sure what I'd do with the product... Perhaps use it in a second experiment to determine whether cinnamoyl chloride can chlorinate GAA or anhydrous sodium acetate to produce acetyl chloride. (No doubt the more experienced contributors here probably know whether this is possible or not; but it seems an interesting enough experiment/exercise for relative beginners like myself.)

garage chemist - 12-9-2007 at 14:32

That cannot possibly work... think about the double bond!
I thought it was clear that this reaction was a special case and can't be used for other aldehydes or alcohols?

Better use your cinnamaldehyde to make benzaldehyde via Organikum's method with sodium carbonate- look it up, it is described here.

And get some benzyl alcohol.

Bromide - 12-9-2007 at 15:25

Originally posted by garage chemist
That cannot possibly work... think about the double bond!
I thought it was clear that this reaction was a special case and can't be used for other aldehydes or alcohols?

You're right, of course, and I'm an idiot... For one thing, I screwed up the attribution in my previous reply. While your method (in the first post) is certainly useful, the reference I had in mind is actually the French patent (FR2633616) provided by Nicodem.

Moreover, FR2633616 actually indicates that the method described therein also applies to acetaldehyde--which would make my proposal of producing cinnamoyl chloride to chlorinate acetic acid rather redundant, it seems.