71

Summary of the sections "chemical shift" and "integration"

1. If protons have similar chemical environments, then typically their NMR signals also have similar chemical shifts. It is therefore possible to assign certain characteristic chemical shift ranges to the protons of the various functional groups in organic compounds. (A table with the most common groups can be found here).
2. The chemical shift can be expressed
   1. as the frequency difference Dn between the signal of a standard (usually tetramethylsilane - TMS) and the respective signal of the sample;
   2. as a frequency independent value on the d-scale according to the following formula:
      

      d = (Dn · 106)/ n0  ppm

      where n₀ is the base frequency of the sepectrometer used.
   On the page that covers this topic we also listed the t scale for sake of completeness. However, today it is of little else but historical interest.
3. The intensity of a signal is determined as the area under the curve of an NMR spectrum (Done usually automatically, using a cumulative integral across the full spectral width) (see page 53).
4. The intensity of a signal is proportional to the number of equivalent protons that give rise to it. Therefore the ratio between the intensities of a set of signals is roughly equal to the number of equivalent protons that contribute to each of the signals. (see page 53).