Give reasons for the following:
(i) o-nitrophenol is more acidic than o-methoxyphenol.
(ii) Butan-1-ol has a higher boiling point than diethyl ether.
(iii) (CH3)3C–O–CH3 on reaction with HI gives (CH3)3CI– and CH3–OH as the main products and not (CH3)3C–OH and CH3–I.
Give reasons for the following:
(i) o-nitrophenol is more acidic than o-methoxyphenol.
(ii) Butan-1-ol has a higher boiling point than diethyl ether.
(iii) (CH3)3C–O–CH3 on reaction with HI gives (CH3)3CI– and CH3–OH as the main products and not (CH3)3C–OH and CH3–I.
(i) The nitro group (–NO2) is an electron-withdrawing group. It decreases the density in the O–H bond. Thus, the proton can be easily lost. With the presence of an electron-withdrawing group, the phenoxide ion is more stabilised. Due to the high stability of the phenoxide ion, the acidic nature increases. On the other hand, the methoxy group is an electron-releasing group. It increases the density in the O–H bond. Thus, the proton cannot be given out easily. Thus, the phenoxide ion is less stabilised. Due to this, o-nitrophenol is more acidic than omethoxyphenol.
(ii) Butan-1-ol has a higher boiling point because it contains a hydroxyl group which is capable of hydrogen bonding. Molecules of diethyl ether are incapable of forming hydrogen bonds with each other.
(iii) (CH3)3–C–O–CH3 is an ether with two different alkyl groups, of which (CH3)3−C− , tertiary alkyl group, on reaction with hydrogen halide (HI) forms a tertiary halide. This occurs as the reaction is an SN1 reaction. The reaction involves the formation of a stable carbocation. If the ether has a primary alkyl group, then the reaction follows the SN2 mechanism.
(i) The nitro group (–NO2) is an electron-withdrawing group. It decreases the density in the O–H bond. Thus, the proton can be easily lost. With the presence of an electron-withdrawing group, the phenoxide ion is more stabilised. Due to the high stability of the phenoxide ion, the acidic nature increases. On the other hand, the methoxy group is an electron-releasing group. It increases the density in the O–H bond. Thus, the proton cannot be given out easily. Thus, the phenoxide ion is less stabilised. Due to this, o-nitrophenol is more acidic than omethoxyphenol.
(ii) Butan-1-ol has a higher boiling point because it contains a hydroxyl group which is capable of hydrogen bonding. Molecules of diethyl ether are incapable of forming hydrogen bonds with each other.
(iii) (CH3)3–C–O–CH3 is an ether with two different alkyl groups, of which (CH3)3−C− , tertiary alkyl group, on reaction with hydrogen halide (HI) forms a tertiary halide. This occurs as the reaction is an SN1 reaction. The reaction involves the formation of a stable carbocation. If the ether has a primary alkyl group, then the reaction follows the SN2 mechanism.
