Chapter 18, Problem 18.15P

Interpretation Introduction

Interpretation:

Following compounds proponamide and N,N-dimethylformamide stractural formula have to be accounded with the help of given ${}^{\text{1}}\text{H NMR}$ details.

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 $\left(\text{N+1}\right)$ 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.

Chemical shift: The NMR spectrum of any compound is taken with reference to a standard compound called reference compound.  Generally, tetramethylsilane (TMS) is taken as the reference compound. The methyl protons of TMS are equivalent and produces only one sharp peak at the rightmost end of the scale.

The distance between the TMS signal and the signals produced by the compound is called the chemical shift.  Chemical shift basically measures the shift in the signal position of the compound with respect to the reference signal.

Chemical shift in delta scale is given as,

$\text{chemical shift,}\delta \left(\text{ppm}\right)=\frac{\text{distance from the TMS signal}\left(\text{Hz}\right)}{\text{operating frequency of the spectrometer (MHz)}}$