Consider the following compounds: $\text { (i) } \mathrm{C}_6 \mathrm{H}_5 \mathrm{COCl}$ The correct…

Consider the following compounds: $\text { (i) } \mathrm{C}_6 \mathrm{H}_5 \mathrm{COCl}$

The correct decreasing order of their reactivity towards hydrolysis is:

1. (i) $ > $ (ii) $ > $ (iii) $ > $ (iv)
2. (iv) $ > $ (ii) $ > $ (i) $ > $ (iii)
3. (ii) $ > $ (iv) $ > $ (i) $ > $ (iii)
4. (ii) $ > $ (iv) $ > $ (iii) $ > $ (iv)

Solution

Electron withdrawing group increases the positive charge and electron releasing group decreases the negative change. The degree of hydrolysis increases as the magnitude of positive charge on carbonyl group increases. Among these $\mathrm{NO}_2$ & $\mathrm{CHO}$ are electron withdrawing group from which $\mathrm{NO}_2$ has more $-\mathrm{I}$ effect than-CHO. On the other hand $\mathrm{CH}_3$ is a electron releasing group. Thus, the order of reactivity towards hydrolysis is Related Theory The mesomeric effect is negative $(-M)$ when the substituent is an electron-withdrawing group and the effect is positive $(+M)$ when the substituent is an electron donating group.

Asked in: NEET 2007

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