Chapter 15, Problem 62IP

Interpretation Introduction

Interpretation:

The isomer from the given molecular formula that produce strong signal at $\text{M-15}$ in mass spectrum should be determined and the reason should be explained.

Concept Introduction:

Mass spectroscopy: It is a form of spectroscopic technique which is used for the elucidation of the molecules, depending upon the mass of the molecule.

$\text{M+1}$ peak: It denotes the peak that arises next to molecular ion peak in the mass spectrum. The $\text{M+1}$ peak in mass spectroscopy is used to explain the number of carbon atoms present in the molecule. The peak arises due to the presence of the isotope of carbon $\left({}^{\text{13}}\text{C}\right).$

Molecular ion peak: It is defined as the heaviest peak in the IR spectrum of the molecule which represents the largest molecular ion in the given molecule with greater m/z value.

Base peak: It is the tallest peak in the spectrum.

The Hydrogen Deficiency Index (HDI): It is used to measure the number of degrees of unsaturation (double and triple bonds) present in a given molecule. It is determined by using the formula

$\begin{array}{l}\text{HDI}\text{=}\frac{\text{1}}{\text{2}}\text{[(2}\times \text{No}\text{. of Carbon atoms)+2+(No}\text{. of Nitrogen atoms)}\\ \text{-(No}\text{. of Hydrogen atoms)-(No}\text{. of halogens)]}\end{array}$

Resonance: The delocalization of pi electrons or lone pair of electrons present in p orbital within the molecule. The molecule is said to be more stable if it is resonance stabilized.

Resonance stabilization: Due to the delocalization of electrons within the molecule the overall energy becomes lower and makes that molecule more stable.

Constitutional Isomers: Two compounds are said to be constitutional isomers if they have same molecular formula but different in their connectivity.

To determine: The isomer that shows strong signal at value $\text{M-15}$.