Chapter 14, Problem 72IP

Interpretation Introduction

Interpretation: The isotope pattern in mass spectrum for the given compound with molecular formula ${\text{C}}_{\text{90}}{\text{H}}_{\text{1}}{}_{\text{80}}{\text{Br}}_{\text{2}}$ should be determined.

Concept Introduction:

Mass spectroscopy: It is a form of spectroscopic technique which is used for the elucidation of the molecular formula and molecular weight of the compound, depending upon the mass of the molecule.

Molecular formula: It represents the types of atoms with their total number present in a given molecule.

Molecular ion peak ${\text{(M)}}^{\text{+}·}$: 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 ${\text{(M+1)}}^{\text{+}·}$ peak: It denotes the peak that arises next to molecular ion peak in the mass spectrum. The peak arises due to the presence of the isotope of carbon since carbon has one isotope $\left({}^{\text{13}}\text{C}\right).$

The ${\text{(M+1)}}^{\text{+}·}$ peak in mass spectroscopy is used to explain the number of carbon atoms present in a molecule depending on the abundance of ${\text{(M+1)}}^{\text{+}·}$ peak.

The ${\text{(M+2)}}^{\text{+}·}$ peak: It denotes the peak that arises next to molecular ion peak in the mass spectrum with respect to the presence of major isotopes in the molecule especially it is used to find the presence of chlorine and bromine since they has two isotopes.

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

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

Isotopes: The elements with same atomic number but with different mass number are said to be isotopes of each other.

To determine: The isotope pattern for the given compound in mass spectrum.