Additive chemical shift parameters for methylene protons. Shoolery's constants reinvestigated

Abstract Methylene proton chemical shifts have been studied using multiple linear regression analysis, and additive chemical shift parameters have been determined. Using a data set of 1007 chemical shifts, involving 48 different substituents, a standard error of estimate of 0.15 ppm was found for protons spread between 2.0 and 5.9 ppm. Provision was made in the data matrix for substituent effects for directly attached groups (α) and for groups attached via one intervening saturated carbon (β‐substituents). The influence of groups more remotely located was assumed to be negligible. Although the parameters were optimized for deshielded methylene proton shifts, they also serve satisfactorily for the estimation of shifts in more shielded methylene cases.