The
degree of saturation (also known as the
index of hydrogen deficiency (IHD) or
rings plus double bonds) formula is used in
organic chemistry to help draw chemical structures. The formula lets the user determine how many rings, double bonds, and triple bonds are present in the compound to be drawn. It does not give the exact number of rings or double or triple bonds, but rather the sum of the number of rings and double bonds plus twice the number of triple bonds. The final structure is verified with use of
NMR,
mass spectrometry and
IR spectroscopy, as well as qualitative inspection.