- Indirect spin-spin coupling occurs
between two or more groups of protons, if these protons are
(Check also page 87 and the
- non-equivalent and
- in sufficient proximity
(i.e., in s
systems they should be in general separated by three or fewer s-bonds).
- The multipilcity of the fine
structure in the NMR signal of a group of protons A
due to spin-spin coupling
(Check page 95 for detailed
- a single neighboring group X with nX equivalent protons
can be predicted by using the following formula:
- with multiple distinct
neighboring groups of protons M,
X, ... with
... equivalent protons can be predicted using the following formula:
|MA = (nM + 1) · (nX + 1) ...
- The intensities of the individual lines
of a multiplet caused by interactions with a neighboring group of
protons follow a pattern similar to the factors in a n-th
degree binominal equation.
(Check page 78. for detailed
- The coupling constant JAX is a measure of the
intensity of the indirect spin-spin coupling between the two protons A and X.
It is defined as:
||Distance between two adjacent
individual lines in the multiplet signal of the proton group A, caused by the coupling with the
group X, in Hertz.
The value of the coupling constant is independent of the working
frequency of the spectrometer.
A list of typical values for coupling constants can be at this site Spectroscopic
Tools at the Potsdam University. (You might also want to
review page 81 and the links
branching from there).
You have now officially earned a short break before you move on to page 109, where you will tackle a
couple of simple structural problems using 1H-NMR