Sciencemadness Discussion Board

Formation of a Vinyl Sulfonate (why use trimethylamine)

ChermNerd22 - 24-3-2012 at 14:54

Hi all, newbie here. I recently started a new job where I am the only synthetic chemist so I need somewhere to bounce ideas off 'real' chemists ;) ... hope you can help.

I wish to add 2-chloroethanesulfonyl chloride to an alcohol then eliminate the chloride on the ethyl chain to form the vinyl sulfonate group.

From Lit:

R-OH + ClSO2CH2CH2Cl -> R-SO2CH=CH2

i) NMe3, DCM
ii) Na2CO3, H2O

My question is, why use trimethylamine (TMA), I have never used TMA (and don't particularly want to as it's a gas). As this a simple SN2 substitution does the TMA just act as a non-nucleophilic base, and if so, could I just substitute it for triethylamine-NEt3 (or am I missing something?)

Thanks in advance.

Is this where I should post such questions?

I guess there's no ChemDraw type plug-in for this forum?

Nicodem - 25-3-2012 at 02:40

Quote: Originally posted by ChermNerd22  
My question is, why use trimethylamine (TMA), I have never used TMA (and don't particularly want to as it's a gas). As this a simple SN2 substitution does the TMA just act as a non-nucleophilic base, and if so, could I just substitute it for triethylamine-NEt3 (or am I missing something?)

Obviously nobody can answer you because you forgot to include the reference. How can we know why trimethylamine was used if we cannot read the article?
Quote:
Is this where I should post such questions?

The topic is organic chemistry, but the discourse you use is not scientific, because you provided no references. Thus you should open this thread in the Beginnings section. But since I take it you'll fix that slip as soon as possible, I'll leave the thread here. You can also read the forum's guidelines for posting if you wish.
Quote:
I guess there's no ChemDraw type plug-in for this forum?

No. It would be quite pointless to have a plug-in based viewer when we already have a the attach file function. You just attach the scheme as a GIF and it will be display in the post.

ChermNerd22 - 25-3-2012 at 12:53

The reference is: JACS, Vol. 104, No. 25, 1982, pg 7108-7122

Nicodem - 26-3-2012 at 09:13

Quote: Originally posted by ChermNerd22  
My question is, why use trimethylamine (TMA), I have never used TMA (and don't particularly want to as it's a gas). As this a simple SN2 substitution does the TMA just act as a non-nucleophilic base, and if so, could I just substitute it for triethylamine-NEt3 (or am I missing something?)

I don't have the time to read the whole article, but already at its second page the authors describe the role of trimethylamine which is not only an HCl scavenger and the reaction is not "a simple SN2 substitution" at all. Trimethylamine is used to form the betylate intermediate which undergoes a reversible E1cB to give the vinylsulfonates. I wouldn't know if triethylamine could be equally efficient. It is less nucleophilic so it might have troubles forming the intermediate rapidly enough to compete with possible side reactions. Perhaps there is an explanation in the article further on in the discussion. Have you read it carefully? Also, why don't you just try it out with triethylamine? Otherwise, you might invest some time into adapting the method by using a combination of trimethylamine hydrochloride and diisopropylethylamine or some other inert base to form the trimethylamine in situ. Or just buy a small cylinder of trimethylamine with a needle valve and dissolve it in CH2Cl2 to be used in an addition funnel. I'm sure it would work just as well as liquid trimethylamine.