Shoolery's rule, which is named after James Nelson Shoolery, is a good approximation of the chemical shift ô of methylene groups in proton nuclear magnetic resonance. We can calculate shift of the CH<sub>2</sub> protons in a AâÂÂCH<sub>2</sub>âÂÂB structure using the formula
where 0.23 ppm is the chemical shift of methane and the empirical adjustments are based on the identities of the A and B groups:
Shoolery's rule is a particular instance of a general class of rules of the form
with two substituents on methylene resulting in two parameters and .