nucleophilic substitution reactions
molecular masses. Primary amines tend to have boiling points intermediate between those of the corresponding alcohol and alkane. Moreover, secondary and tertiary amines have lower boiling points than primary amines of comparable molecular mass. Tertiary amines form cations analogous to the ammonium ion NH 4+ , in which all four H atoms are replaced by alkyl groups. Such substances, calledquaternary ammonium salts, can be chiral if all four substituents are different. Amines with three different substituents are also chiral because the lone pair of electrons represents a fourth substituent. Alkylamines can be prepared by nucleophilic substitution reactions of alkyl halides with ammonia or other amines: Equation 24.12.