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Topic: Lactic acid + SOCl2 to give C6H8O4  (Read 3020 times)

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Offline Altered State

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Lactic acid + SOCl2 to give C6H8O4
« on: May 05, 2013, 01:16:05 PM »
The treatment of lactic acid with SOCl2 gives a C6H8O4 product.

I need to draw the structure and the mechanism that gives the product.

I know that any carb. acid with SOCl2 undergoes An + E reaction and gives the acid chloride. I tried, but I cannot figure out a way of drawing a mechanism in which the product is one of that formula.
I guess 2 of the starting molecules would combine in any step, but I cannot see how.
Any thoughts?

Offline opsomath

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Re: Lactic acid + SOCl2 to give C6H8O4
« Reply #1 on: May 06, 2013, 10:11:32 AM »
Quote
I guess 2 of the starting molecules would combine in any step, but I cannot see how.

Quote
I know that any carb. acid with SOCl2 undergoes An + E reaction and gives the acid chloride.

So say you make the acid chloride. What reaction can happen then?

Offline Babcock_Hall

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Re: Lactic acid + SOCl2 to give C6H8O4
« Reply #2 on: May 06, 2013, 11:07:22 AM »
@OP, In general into what other classes of compounds can acid chlorides be converted?

Offline Altered State

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Re: Lactic acid + SOCl2 to give C6H8O4
« Reply #3 on: May 07, 2013, 02:02:11 PM »
I think I got it:

Lactic acid reacts with SOCl to give the corresponding acid chloride.
Then 2 moleculoes of that cholride acid can reac, each of then with it's OH group acting as nucleophile  and undergoing firstly a nucleophilc additon intermolecular, and then, the other OH group can reat with the other carbonyl undergoing another An, givig as result a cyclic double ester, "double lactone".

Offline opsomath

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Re: Lactic acid + SOCl2 to give C6H8O4
« Reply #4 on: May 07, 2013, 02:38:58 PM »
Yep. That's a pretty good description.

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