The carboxylic acid with the highest pK_{a} a | vedclass

Name: Exam Paper Generator | JEE NEET Paper Generator | Vedclass
Brand: Vedclass
Rating: 5 (35 reviews)

Question

(D) The acidity of substituted benzoic acids depends on the electronic effects of the substituents. Electron-withdrawing groups $(EWG)$ increase acidi

Vedclass · Accepted Answer

$III, IV$

Vedclass · Answer

(D) The acidity of substituted benzoic acids depends on the electronic effects of the substituents. Electron-withdrawing groups $(EWG)$ increase acidity (lower $pK_{a}$),while electron-donating groups $(EDG)$ decrease acidity (higher $pK_{a}$).$1$. $III$ ($p$-methylbenzoic acid): $-CH_3$ is an $EDG$ ($+I$ and hyperconjugation effect),which decreases acidity. Thus,it has the highest $pK_{a}$.$2$. $I$ ($p$-iodobenzoic acid): $-I$ is a weak $EWG$ ($-I$ effect),which slightly increases acidity.$3$. $II$ ($p$-cyanobenzoic acid): $-CN$ is a strong $EWG$ ($-I$ and $-M$ effects),which significantly increases acidity.$4$. $IV$ ($p$-nitrobenzoic acid): $-NO_2$ is a very strong $EWG$ ($-I$ and $-M$ effects),which increases acidity the most. Thus,it has the lowest $pK_{a}$.Therefore,the highest $pK_{a}$ is for $III$ and the lowest $pK_{a}$ is for $IV$. The correct option is $D$.

The carboxylic acid with the highest $pK_{a}$ and lowest $pK_{a}$ values among the following are respectively:

Similar Questions

What product is obtained when acetamide is heated with $P_2O_5$?

Which one of the following orders of acid strength is correct?

What is obtained when the silver salt of a fatty acid is refluxed with an alkyl halide?

Which among the following has the highest boiling point?

Which of the following does not give Claisen condensation reaction?

Vedclass Test Series

Exam Paper Generator

Online Exam Module