Give reasons for the following:

(a) Aldehydes and ketones have lower boiling points than corresponding alcohols.

(b) Chloroacetic acid is stronger than acetic acid.

(c) Formaldehyde does not take part in aldol condensation.

(a) Aldehydes and ketones have lower boiling points than corresponding alcohols as molecules in alcohols are held together by hydrogen bonding, which have to be broken to vaporise while such bonding is absent in aldehydes and ketones. Hence alcohols of corresponding aldehydes and ketones require higher temperatures to boil.

(b) Acidic character is determined by the ease with which H⁺ ions are lost(donated).

Chlorine is highly electronegative and exhibits –I effect(draws electron density towards itself) leaving a delta positive charge on oxygens in chloroacetic acid. As oxygen is also electronegative in nature, positive charge on it is not stable, so to compensate for the positive charge it loses H⁺ readily, making it more acidic than acetic acid.

(c) For an aldehyde to undergo aldol condensation α-hydrogen is required, which is absent in formaldehyde, hence does not undergo aldol condensation.