CBSE 2014, Set 1

Question

(a) Account for the following:
(i) $Cl - CH_2COOH$ is a stronger acid than $CH_3COOH$.
(ii) Carboxylic acids do not give reactions of carbonyl group.

(b) Write the chemical equations to illustrate the following name reactions:
(i) Rosenmund reduction
(ii) Cannizzaro's reaction

(c) Out of $CH_3CH_2-CO - CH_2 - CH_3$ and $CH_3CH_2- CH_2- CO - CH_3$, which gives iodoform test?

Edvaya · Accepted Answer

The correct answer is Subjective. **SOLUTION** (a) (i) $Cl-CH_2COOH$ is a stronger acid than $CH_3COOH$ Substitution of electron withdrawing group on carboxylic acid affects the acidity of carboxylic acid. Chlorine is an electron withdrawing group and it increases the acidity of carboxylic acids by stabilising the conjugate base due to delocalisation of the negative charge by resonance effects. (ii) Lone pairs of electrons present in carboxylic acid are involved in resonance due to this the electrophilic character of carbon in carboxylic acid decreases. Thus, it does not show the reactions of carbonyl group. ![Resonance](https://www.edvaya.com/img/40.png) (b) (i) Rosenmund reduction ![Rosenmund Reduction](https://www.edvaya.com/img/41.png) (ii) Cannizzaro's reaction ![Cannizzaro's Reaction](https://www.edvaya.com/img/42.png) (c) Pentan-2-one ($CH_3-CH_2-CH_2-CO-CH_3$) gives iodoform test i.e., it gives yellow precipitate of $CHI_3$ with NaOI ![Reaction](https://www.edvaya.com/img/43.png)

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Chemistry > Organic Chemistry > Aldehydes Ketones And Carboxylic Acids

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