Question

Primary amines have higher boiling points than tertiary amines. State whether this statement is true or false.

Answer 1

Hint- Here, we will proceed by defining amines and we will also mention some important features of amines. Then, we will discuss about primary and tertiary amines. Finally, we will be discussing the reason behind primary amines having higher boiling point as compared to tertiary amines.

Complete answer:
Amines are referred as any member of a family of nitrogen-containing organic compounds that is derived, either in principle or in practice, from ammonia (${\text{N}}{{\text{H}}_3}$).
Some basic features of amines are:

$1.$ Due to the lone pair of electrons, amines are basic compounds. The basicity of the compound can be influenced by neighbouring atoms, steric bulk, and the solubility of the corresponding cation to be formed.
$2.$ Amine compounds can hydrogen bond, which affords them solubility in water and elevated boiling points.
$3.$ The general structure of an amine is a nitrogen atom with a lone pair of electrons and three substituents. However, the nitrogen may bind to four substituents, leaving a positive charge on the nitrogen atom. These charged species can serve as intermediates for important reactions.

Amines are categorized into three different types which are primary amines, secondary amines and tertiary amines.
Primary amines- In primary amines, only one of the hydrogen atoms in the ammonia molecule has been replaced. That means that the formula of the primary amine will be ${\text{RN}}{{\text{H}}_2}$ where R is an alkyl group.
Tertiary amines- In a tertiary amine, all of the hydrogens in an ammonia molecule have been replaced by hydrocarbon groups.
Primary amines have higher Hydrogen bonding than tertiary amines due to the steric hindrance of the bulky alkyl group, Amines have a greater tendency to form hydrogen bonding due to the presence of hydrogen and N atoms. The intermolecular bonding increases and will require more energy to break the bonds.
Mostly in primary amines two hydrogens are present that form a stronger hydrogen bond as compared to tertiary amines hence it has a higher boiling point.
Therefore, the given statement i.e., primary amines have higher boiling point than tertiary amines is true.

Note- In a secondary amine, two of the hydrogens in an ammonia molecule have been replaced by hydrocarbon groups. Amines have lower boiling points as compared to those of alcohols and carboxylic acid of comparable molar masses because hydrogen bonding in amines is not as strong as alcohol molecules.