COMPARISON OF EMPIRICAL EQUATIONS FOR PREDICTING C-13 CHEMICAL-SHIFTS IN HYDROCARBONS, AMINES, CARBOXYLIC-ACIDS, AND AMINO-ACIDS

Published data for the C-13 chemical shifts of hydrocarbons were analyzed with multiple linear regression techniques to obtain predictive equations for these shifts. These equations were based on the sum of parameter terms, and parameter types proposed by various investigators were compared. Published C-13 chemical shift data for amines, carboxylic acids, and compounds containing both polar groups, at their various ionization states in water, were supplemented with newer data. Computational experiments were done to determine which types of carbon atoms were sufficiently similar to fit the same predictive equation for chemical shifts without significant loss of accuracy. Eight equations were found to be necessary. © 1979.