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
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:
| Substituent | S / ppm |
| –CH3 | 0.47 |
| –COOR | 1.55 |
| –COR | 1.70 |
| –C6H5 | 1.83 |
| –SR | 1.64 |
| –I | 1.82 |
| –Br | 2.33 |
| –OR | 2.36 |
| –Cl | 2.53 |
| –OH | 2.56 |
| –OCOR | 3.13 |
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.