Chapter 16, Problem 16.12P

Interpretation Introduction

Interpretation:

Suppose that a proton’s chemical shift is $\text{2}\text{.4 ppm}$ in a $\text{300MHz}$ NMR spectrometer. The difference between the signal frequency of that proton and the signal frequency of a proton in TMS is to be calculated.

Concept introduction:

Chemical shift is a measure of the extent to which a signal’s frequency differs from that of a reference compound. The reference compound used for $\text{H}$ NMR spectroscopy is TMS. Formally, chemical shift, in units of parts per million (ppm), is defined by the mathematical expression

$\text{Chemical shift (ppm) = }\frac{{\text{ν}}_{\text{sample}}{\text{-ν}}_{\text{TMS}}}{{\text{ν}}_{\text{op}}}{\text{×10}}^{\text{6}}$.

Here, ${\text{ν}}_{\text{sample}}$ is the frequency of the signal of interest, ${\text{ν}}_{\text{TMS}}$ is the frequency of the signal from the protons in TMS, and ${\text{ν}}_{\text{op}}$ is the operating frequency of the NMR spectrometer, all of which are in units of hertz (Hz).