Alpha-substituent effects on 13C NMR chemical shifts in some carbonyl compounds

The principal component analyses of α-substituent effects on 13C NMR chemical shifts for 36 carbonyl compounds are presented. The data matrix, 36x17, consisted of 15 independent and 2 class variables. α-Mono substituted acetones (12 samples), acetophenones (8 samples), cyclohexanone (8 samples) and camphors (8 samples) are discriminated in four groups due to the differences in LUMO energies and carbonyl carbon chemical shifts. Furthermore, these compounds exhibit strong separation in neutral compounds, nitrogen derivatives (NMe2 and NEt2) and sulfur compounds (SMe and SEt), while halogenated compounds exhibit different behavior. (author)