Chapter 2, Problem 52P

Interpretation Introduction

Interpretation:

The structure for all the compounds with the molecular formula ${\text{C}}_{\text{4}}{\text{H}}_{\text{6}}\text{O}$ that would not exhibit infrared absorption in $3200-3500{\text{ cm}}^{-1}$ and $1620-1780{\text{ cm}}^{-1}$ regions is to be written.

Concept introduction:

Infrared spectroscopy is a simple, instrumental technique, which helps to determine the presence of various functional groups.

It depends on the interactions of atoms or molecules with the electromagnetic radiation.

The molecules that have dipole moment are IR active and the molecules that do not have dipole moment are IR inactive.

The carbon–carbon double bond $\left(\text{C}=\text{C}\right)$ gives IR absorption peak at $1620-1680{\text{ cm}}^{-1}$.

The carbon–carbon triple bond $\left(\text{C}\equiv \text{C}\right)$ gives IR absorption peak at $2100-2260{\text{ cm}}^{-1}$.

The alcohol or phenol $\left(\text{O}-\text{H}\right)$ gives IR absorption peak at $3200-3550{\text{ cm}}^{-1}$.

The ether $\left(\text{C}-\text{O}\right)$ gives IR absorption peak at $1020-1275{\text{ cm}}^{-1}$.

Degree of unsaturation is the calculation that determines the total number of rings and pi-bonds.

It is used in organic chemistry to draw chemical structures.

Mathematically, the degree of unsaturation is expressed as

$\text{DoU}=\left(\frac{2\text{C}+2+\text{N}-\text{H}-\text{X}}{2}\right)$

Here, $\text{C}$ is the number of carbon atoms, $\text{N}$ is the number of nitrogen atoms, $\text{H}$ is the number of hydrogen atoms, and $\text{X}$ is the number of halogen atoms.