Decarboxylation of beta-keto esters?

Question

hi,
so, i know that carboxylic acids don't usually undergo decarboxylation.
now, when beta-keto ester is heated, CO2 is lost. can anyone tell me why this occurs? and what's its importance in organic synthesis... other than being a method for producing methyl ketones.
thank you

Answer 1

You can see a nice example where this reaction is used (together with other ones) to produce a cyclic ketone from a linear dicarboxy ester at http://chemistry2.csudh.edu/rpendarvis/carb-enolate.html#synth

There are plenty of things you can do with beta-ketoesters (like forming carbanions and then elongating the molecule with appropriate alkyl-halogens).

I think decarboxylation occurs because there is a cyclic transition state which favours it:

.... .. .. ...H
... .... .... ..\
.. ... O ... .. O
.. .. .|| ... ... .|
.. R-C.. ... .. C=O
.. ... ..\ ...... ../
... .... ..CH2

The H hops onto the carbonylic O, and an enol is formed while CO2 is expelled. The enol tautomerizes then in to the ketone. If you add Br2 from the beginning of the reaction the enol will react and you'll get a bromoketone, proving the mechanism.

Answer 2

plz dont ask questions just for the sake of asking it......
That's what decarboxilation means...............
loss of a molecule of CO2.
when any substance is heated it wants to come to its more thermodynamically stable form hence changes occurs..........
fine................I hope u understand