Chapter 12C, Problem 45P

Interpretation Introduction

Interpretation: The signals due to ${\text{H}}_{\text{a}}{\text{, H}}_{\text{b}}\text{,}$ and ${\text{H}}_{\text{c}}$ in the ${}^{\text{1}}\text{H}$ NMR spectrum of acrylonitrile $\left({\text{CH}}_{\text{2}}=\text{CHCN}\right)$ are to be labeled. A splitting diagram for the absorption due to the ${\text{H}}_{\text{a}}$ proton is to be drawn.

Concept introduction: The number of NMR signal in a compound is equal to the number of chemically non-equivalent protons present in that compound. In ${}^1\text{H}-\text{NMR}$ all chemically equivalent protons generates one signal or one peak, whereas non-equivalent proton generates different signals.

The distance between any two adjacent peaks is called coupling constant which is represented by $J$. The coupling constant gives vital information about the adjacent groups or protons.