Question

Tetramethylsilane (TMS) is the accepted internal standard for calibrating chemical shift ppm values for 1H, 13C, and 29Si NMR spectroscopy in organic solvents.

In 1H-NMR, the TMS peak is assigned 0 ppm. This is upfield of most proton peaks observed for organic compounds. Briefly explain why the protons in TMS appear at this upfield location in a 1H-NMR spectrum.

Considering the range of hertz values possible for a spectrometer, why is the ppm scale used? To what does the ppm scale refer?

Answer 1