Simulation of 13C N.M.R. Spectra of Nitrogen-Containing Aromatic Compounds

Abstract

The 13C n.m.r. spectra of a series of nitrogen-containing aromatic compounds have been simulated by using parametric techniques. The observed chemical shifts were related to numerically encoded structural parameters, called descriptors. The electronic and geometric descriptors were calculated after optimization of the molecular structures by using the MNDO semiempirical method. Subsequently, the method of stepwise, multiple linear regression was used to calculate coefficients relating the descriptors to the observed chemical shifts. This study involves 32 compounds such as pyridine, pyrimidine, triazine, pyridazine, and their methyl derivatives. Plotting of experimental against calculated chemical shifts for 23 carbon centres in the prediction set of five compounds shows a standard deviation of 1.41 ppm and a correlation coefficient of 0.999.