RE: ORGLIST: Use of phosphorus pentachloride in acid chloride synthesis

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From: will jones (willjones46$##$hotmail.com)
Date: Tue Oct 25 2005 - 10:24:52 EDT


If you are carrying out an esterification, then use coupling agents such as
DCC. the reaction is best carried out in dcm if you can, although I use dcc
in loads of solvents. the product, dcu is easily separated as it is
insoluble in most solvents. You can carry out the coupling reaction with the
carboxylic acid and alcohol in situ.

This is much easier than using PCl5.

Will


>From: cardman <cardman400$##$yahoo.com>
>To: everybody$##$orglist.net
>Subject: ORGLIST: Use of phosphorus pentachloride in acid chloride
>synthesis
>Date: Mon, 24 Oct 2005 18:04:39 -0700 (PDT)
>
>Does anyone have any tips on the use of PCl5 ? I tried
>using a 1:1 molar ratio of pentachloride and
>4-azidobenzoic acid in refluxing benzene and got a
>yield of only 50% of the acid chloride. Of course I
>thought about using a large excess of chloride to
>drive the rxn forward, but then how do I separate off
>the xs? I want to carry out an esterification, so I
>can't just use the reaction mixture as it is (or can
>I?).
>
>Actually, the same thing happened with oxalyl
>chloride: I recrystallized the residue, and a
>significant portion of the unreacted acid crystallized
>out first.
>
>I can't use thionyl chloride because my company has to
>first apply for a permit. Apparently thionyl chloride
>is on the DEA's list of restricted chemicals.
>
>
>
>
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