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Question

Chemistry Question on Aldehydes, Ketones and Carboxylic Acids

Which one of the following have lowest pKapK_a?

A

ClCH2CH2COOHClCH_2CH_2COOH

B

Cl2CHCH2COOHCl_2CHCH_2COOH

C

ClCH2COOHClCH_2COOH

D

Cl2CHCOOHCl_2CHCOOH

Answer

Cl2CHCOOHCl_2CHCOOH

Explanation

Solution

Chlorine has the highest - II effect at the a position. Since ClCH2COOHClCH_2COOH has only one αCl\alpha - Cl atom and Cl2CHCOOHCl_2CHCOOH has two αCl\alpha - Cl atoms; therefore, CHCl2COOHCHCl_2COOH is a strongest acid among all and has lowest pKapK_a value.