A. Chemical Shifts
Internal Standard: Peak positions are measured relative
to an internal standard that is placed in the NMR tube with the sample.
Tetramethylsilane (TMS) (CH3)4Si
- the standard
used for organic solvents
units of d (delta) scale: 1d =
1 ppm
1 ppm = 1 part per million of the spectromet. operating
frequency (eg. 300 MHz)
The d scale is therefore independent of
the spectrometer frequency.