Explain the mechanism of nucleophilic addition reactions of aldehyde and ketone compounds.

(N/A) The mechanism of nucleophilic addition to the carbonyl group involves the following steps:
$(i)$ $A$ nucleophile $(Nu^-)$ attacks the electrophilic carbon atom of the polar carbonyl group from a direction approximately perpendicular to the plane of the $sp^2$ hybridized orbitals of the carbonyl carbon.
$(ii)$ Slow step-$1$: The hybridization of the carbon changes from $sp^2$ to $sp^3$ in this process,and a tetrahedral alkoxide intermediate is produced.
$(iii)$ Fast step-$2$: The alkoxide intermediate captures a proton from the reaction medium to form the final addition product.

Compound (Type)	Boiling Point $(K)$
$n$-Butane (Hydrocarbon)	$273$
Methoxyethane (Ether)	$281$
Propanal (Aldehyde)	$322$
Acetone (Ketone)	$329$
Propan-$1$-ol (Alcohol)	$370$

The boiling points of aldehydes and ketones are lower than those of alcohols of similar molecular masses due to the absence of intermolecular hydrogen bonding. They exhibit weak intermolecular association due to dipole-dipole interactions between the opposite ends of the $C=O$ dipoles.