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32
Subjective

Carboxylic acids contain carbonyl group but do not show the nucleophilic addition reaction like aldehydes or ketones. Why?

Explanation

Carboxylic acid contain carbonyl group but do not show nucleophilic addition reaction like aldehyde and ketone. Due to resonance as shown below the partial positive charge on carbonyl carbon atom is reduced.

33
Subjective

Identify the compounds A, B and C in the following reaction.

$\mathrm{CH}_3-\mathrm{Br} \xrightarrow{\text { Mg/ether }}[A] \xrightarrow[\text { (i) Water }]{\text { (i) } \mathrm{CO}_2}[B] \xrightarrow[\Delta]{\mathrm{CH}_3 \mathrm{OH} / \mathrm{H}^{+}}[C]$

Explanation

Complete chemical conversion can be done as

34
Subjective

Why are carboxylic acids more acidic than alcohols or phenols although all of them have hydrogen atom attached to a oxygen atom ( $-0-\mathrm{H}$ )?

Explanation

Carboxylic acids are more acidic than alcohol or phenol, although all of them have $\mathrm{O}-\mathrm{H}$ bond. This can be explained on the basis of stability of conjugate base obtained after removal of $\mathrm{H}^{+}$from acid or phenol.

Hence, dissociation of $\mathrm{O}-\mathrm{H}$ bond in case of carboxylic acid become easier than that of phenol. Hence, carboxylic acid are stronger acid than phenol.

35
Subjective

Complete the following reaction sequence.

Explanation

The complete chemical transformation can be shown as

36
Subjective

Ethyl benzene is generally prepared by acetylation of benzene followed by reduction and not by direct alkylation. Think of a possible reason.

Explanation

Preparation of ethyl benzene from acylation of benzene and reduction can be shown as

The direct alkylation can not be performed because there is polysubstitution product is formed. Due to disadvantage of polysubstitution that Friedel-Craft's alkylation reaction is not used for preparation of alkylbenzenes. Instead of Friedel-Craft's acylation is used.