Chapter 15.10, Problem 19P

Interpretation Introduction

Interpretation:

${}^{\text{1}}\text{H NMR}$ spectra of 1-chloropropane and 1-iodopropane has to be identified.

Concept introduction:

The Single ${}^{\text{1}}\text{H NMR}$ signal is split into multiple peaks called the multiplicity of the signal.  Splitting of signals is done according to the $\left(N+\text{1}\right)$) rule.  N is the number of adjacent non equivalent protons.  According to the $\left(N+\text{1}\right)$ rule, for a proton-coupled with N adjacent non equivalent protons, the signal split into $\left(N+\text{1}\right)$ peak.  The splitting is mutual.

For example, in propane

$\left(\text{C}\underset{\text{a}}{{\text{H}}_{\text{3}}}-\text{C}\underset{\text{b}}{{\text{H}}_{\text{2}}}-\text{C}\underset{\text{a}}{{\text{H}}_{\text{3}}}\right)$

The signal produced by ‘a’ protons split into 3 peaks due to the adjacent ‘b’ protons called as a triplet calculated as,

$\begin{array}{c}\left(N_{\text{b}}+1\right)=\left(2+1\right)\\ =3\end{array}$

Here $N_{\text{b}}$ is the number of ‘b’ protons.

The signal produced by ‘b’ protons is split into 4 peaks due to the adjacent nonequivalent ‘a’ protons called as a quartet calculated as,

$\begin{array}{c}\left(N_{\text{a}}+1\right)=\left(3+1\right)\\ =4\end{array}$

Here $N_{\text{a}}$ is the number of ‘a’ protons.

Splitting occurs only due to nonequivalent protons that are the protons present in the different chemical environment.