Chapter 16, Problem 16.40P

Interpretation Introduction

Interpretation:

At room temperature, $N,N\text{-dimethylformamide}$, $\text{HCON}{\left({\text{CH}}_{\text{3}}\right)}_{\text{2}}$ has three ${}^{\text{1}}\text{H}$ NMR signals, appearing at $2.9,3.0,$ and $\text{8}\text{.0 ppm}$. How, as the temperature is increased, the two signals at $2.9$ and $\text{3}\text{.0 ppm}$ merge into one signal is to be explained.

Concept introduction:

The protons in different chemical environments interchange rapidly; then they give rise to the same NMR signal that reflects the average of those environments. To cause the NMR lines to be broadened, the NMR time scale of the interchange must be slow enough or fast enough. NMR time scale is the time scale where the broadening occurs.