Chapter 16, Problem 16.72P

Interpretation Introduction

Interpretation:

Compounds X and Y both produce mass spectra in which the ${\text{M}}^{\text{+}}$ peak appears at $\text{m/z = 122}$. In the spectrum of compound X, the relative intensity of the $\text{M+1}$ peak is $\text{83}\text{.2\%}$, and that of the ${\text{M}}^{\text{+}}$ peak is $\text{6}\text{.7\%}$. In the mass spectrum of compound Y, the analogous intensity values are $\text{16}\text{.9\%}$ and $\text{1}\text{.6\%}$. The compound that contains more carbon atoms is to be determined.

Concept introduction:

The number of carbon atoms is calculated by

$\text{Number of C atoms }\approx \frac{\text{Intensity of M+1}}{{\text{Intensity of M}}^{\text{+}}}\times \frac{100\%}{1.1\%}$.

The equation above uses the peak intensities of $\text{M+1}$ and ${\text{M}}^{\text{+}}$ and the relative abundance of $\text{C}\text{/}\text{C}$ to calculate the number of carbon atoms.