Chapter 13, Problem 13.28P

Interpretation Introduction

Interpretation:

Using the given parameters from a partial molecule, the correct NMR spectrum has to be sketched.

Concept Introduction:

The ${}^{1}HNMR$ spectrum of a compound provides some vital information that is required to predict the structure of the compound.  The chemical shift values can predict the groups that are present in the molecule.  The splitting of signals by the $\left(N+1\right)$ rule predicts the number of hydrogens or protons attached to the adjacent carbon in a carbon chain of a compound.  With this information, the structure of the compound can be predicted.

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 nonequivalent protons.  According to the $\left(N+\text{1}\right)$ rule, for a proton-coupled with N adjacent nonequivalent protons, the signal split into $\left(N+\text{1}\right)$ peak.  The splitting is mutual.  Splitting occurs only due to nonequivalent protons that are the protons present in the different chemical environment.

The distance between any two adjacent peaks is called coupling constant in hertz represented as $J$.  The value of coupling constant for two protons coupling with each other is same.  Thus the coupling constant gives vital information about the adjacent groups or protons because protons on adjacent carbons have a similar coupling constant.