Chapter 16, Problem 16.54CP

Interpretation Introduction

Interpretation:

Reason for the difference in the given boiling points of amines (hexyl amine and triethylamine) should be explained.

Concept introduction:

Amines are the derivatives of ammonia $\left(N{H}_3\right)$ with one or more of the hydrogens replaced with a substituent such as an alkyl group.

Depending on the number of carbon side chain of the nitrogen, different types of amines can form.

The boiling points of aliphatic amines are higher than those of alkanes or halo alkanes of similar relative molecular mass due to intermolecular hydrogen bonding.

The $\text{N-H}$ bond is more polar than the $\text{C-H}$ bond but less polar than $\text{O-H}$ bond.

Hydrogen bonding in amine is weaker than that of alcohols or carboxylic acids. Boiling points of amines are lower than those corresponding alcohols or carboxylic acids.

Increasing order of boiling point of some organic compounds with similar molecular weight can be represented as follows,

$\text{Alkane}\text{<}\text{Ether}\text{<}\text{Alkyl}\text{halide}\text{<}\text{Amine}\text{<}\text{Ketone}\text{,}\text{aldehyde}\text{<}\text{Alcohol}\text{<}\text{Carboxylic}\text{acid}$

Hydrogen bond is an attractive force established between hydrogen atom attached to a highly electronegative element and another highly electronegative element of the same or different molecule.

Intermolecular hydrogen bonding:

When hydrogen bonding takes place between various molecules of the same or different compounds, it is called intermolecular hydrogen bonding.

Molecules which have this type of hydrogen bonding possess abnormally high melting and boiling points.

Intramolecular hydrogen bonding:

When hydrogen bonding occurs within the same molecule is termed as intramolecular hydrogen bonding.