Chapter 16, Problem 16.16QAP

Interpretation Introduction

(a)

Interpretation:

The vibrations that can be assigned to strong absorption bands and the possible causes of the weak absorptions is to be stated.

Concept introduction:

In quantum mechanics, the atoms and the molecules are able to withstand only certain defined amount of energies. The absorption bands are the ranges of the frequencies or the wavelengths in the spectrum which are a feature of the transitions from the initial to the final state.

Interpretation Introduction

(b)

Interpretation Whether $\text{HCN}$ is linear or non-linear molecule and the vibrations that can be assigned to the three absorption bands are to be stated.

Concept introduction:

The IR absorption spectroscopy makes use of a mid infrared light that detects the particular types of chemical bonds in a given sample for the purpose of the identification of organic and organomettalic compounds. In the IR absorption spectra, there are two regions: Functional group region and the fingerprint region.

Interpretation Introduction

(c)

Interpretation:

The number of fundamental vibration modes for ${\text{BF}}_{\text{3}}$ and the fundamental vibration modes that are IR active is to be stated.

Concept introduction:

It is necessary to alter the dipole moment of the molecule for a compound to be IR active. Some bonds are able to absorb infrared light more than other molecules whereas some bonds don’t absorb the IR radiations at all.

Interpretation Introduction

(d)

Interpretation:

The number of fundamental vibrational modes for methane, benzene, toluene, ethylene and carbon tetrachloride is to be stated.

Concept introduction:

The molecular vibrations take place when atoms of a molecule are executing periodic motion while the molecules either have constant translational motion or rotational motion. The fundamental vibration is excited when the molecule absorbs one quantum of energy in the ground state.