Consider the following four compounds:
(I) $CH_{3} CH_{2} COOH$
(II) $ClCH_{2} COOH$
(III) $Cl_{2} CHCOOH$
(IV) $CH_{3} CHClCOOH$

How many of these compounds have a higher acidic strength than acetic acid ( $CH_{3} COOH$ )?
(Assume standard conditions)

Question

Consider the following four compounds:

(I) $CH_{3} CH_{2} COOH$

(II) $ClCH_{2} COOH$

(III) $Cl_{2} CHCOOH$

(IV) $CH_{3} CHClCOOH$

How many of these compounds have a higher acidic strength than acetic acid ( $CH_{3} COOH$ )?

(Assume standard conditions)

TestHub · Accepted Answer

The acidic strength of carboxylic acids depends on the stability of their conjugate base. Electron-withdrawing groups (-I effect) stabilize the carboxylate anion, increasing acidity, while electron-donating groups (+I effect) destabilize it, decreasing acidity.

Acetic acid ( $C H_{3} COO H$ ) has a methyl group, which exhibits a +I effect.

(I) $C H_{3} C H_{2} COO H$ (Propanoic acid): The ethyl group ( $C H_{3} C H_{2} -$ ) has a stronger +I effect than methyl, making it weaker than acetic acid.

(II) $ClC H_{2} COO H$ (Chloroacetic acid): Chlorine is an electron-withdrawing group (-I effect), increasing acidity. Stronger than acetic acid.

(III) $C l_{2} C H COO H$ (Dichloroacetic acid): Two chlorines provide a stronger -I effect, making it significantly more acidic than acetic acid.

(IV) $C H_{3} C H ClCOO H$ (2-Chloropropanoic acid): Chlorine at the $α$ -position exerts a strong -I effect, making it stronger than acetic acid.

Compounds (II), (III), and (IV) are more acidic than acetic acid. Thus, 3 compounds have higher acidic strength.

Chemistry - GOC Question with Solution | TestHub

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JEE Advanced 2028 (Class 11)