# How to compare the rate of decarboxylation?

For the following acids compare the rate of decarboxylation on heating

I $$\ce{Ph-CO-CH2COOH}$$

II $$\ce{Ph-CO-COOH}$$

III $$\ce{CH3-CH2-COOH}$$

IV $$\ce{HOOC-CH2-COOH}$$

I tried this question by forming carbanions and comparing their stability. But I am stuck at comparing I and IV.

– Tony
Apr 6, 2020 at 19:17
• @Tony Yeah, (4) Apr 6, 2020 at 20:01
• Yes the ans is 4 but please tell me how did you compare between I and IV ? Apr 6, 2020 at 20:04
• In the mechanism for intramolecular decarboxylation,if you recall,the EWG bature of the carbonyl is responsible for withdrawing electrons from the -COOH part. It won't be able to do that very efficiently in IV due to cross conjugation presented by the OH ,which will decrease it's withdrawing nature Apr 6, 2020 at 23:20
• For comparing the rate of decarboxylation just compare the stability of the carbanion formed. It's an easy jee concept.
– user91688
Apr 7, 2020 at 4:11