Chapter 14, Problem 44P

Interpretation Introduction

Interpretation:

The number of peaks into which the proton signal of the $\text{H}$ NMR spectrum of methyl fluoride would be split and number of peaks into which the fluorine signal in $\text{F}$ NMR spectrum of methyl fluoride would be split is to the determined. The $\text{δ}$ values of the peaks observed in the proton spectrum of methyl fluoride at 300 MHz is to be determined.

Concept introduction:

Splitting of a proton signal is also seen as a result of germinal coupling due to an atom like F which has a nuclear spin of $\text{±}\frac{\text{1}}{\text{2}}$.

The number of peaks into which an NMR signal is split is the same as in the case of vicinal coupling, equal to $\text{n+1}$, here n is the number of coupling atoms in geminal position.

Naturally occurring fluorine is monoisotopic, $\text{F}$, and has a nuclear spin of $\text{±}\frac{\text{1}}{\text{2}}$. As a result, fluorine atom can also split the signal of a proton in a geminal or vicinal position.

The chemical shift and signal frequency are related as

$\text{chemical shift = }\frac{\text{position of signal - position of TMS peak}}{\text{spectrometer frequency}}{\text{ × 10}}^{\text{6}}$