Shoolery's rule

Shoolery's rule, which is named after James Nelson Shoolery, is a good approximation of the chemical shift δ of methylene groups in proton nuclear magnetic resonance. We can calculate shift of the CH₂ protons in a A–CH₂–B structure using the formula

${\displaystyle \delta =0.23\,\mathrm {ppm} +S_{\mathrm {A} }+S_{\mathrm {B} }}$

where 0.23 ppm is the chemical shift of methane and the empirical adjustments S 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

${\displaystyle \delta =b_{0}+\sum _{i}z_{i}}$,

with two substituents on methylene resulting in two parameters ${\displaystyle S_{A}}$ and ${\displaystyle S_{B}}$.^[1]