C-13 NMR CHEMICAL-SHIFT SUBSTITUENT EFFECTS - EMPIRICAL SUBSTITUENT EFFECTS IN BETA-ALCOXYVINYL HALOMETHYLKETONES

This work presents the evaluation by empirically derived equations for the substituent effect (alpha, beta, gamma, delta) on the C-13 NMR ch emical shifts for C-1, C-2, C-3 and C-4 in beta-alcoxyvinylhalomethylk etones 1a-h to 3a-h [R3C(O)-C(R2)=C(R1)- OR, where R1 = H, alkyl or ph enyl, R2 = H, alkyl or hetero-alkyl, and R3 = di- or trihalomethyl], t aking as reference the compound 1a. From the calculated values for the alpha, beta, gamma, delta effects for each substituent it was possibl e to estimate the chemical shift of each carbon of the compounds 1-3. The C-13 chemical shifts of the C-1, C-2, C-3, C-4 of these compounds, can be estimated with good to rasoable precision: 93% of the calculat ed chemical shifts are found to be within +/-2.0ppm, and 100% are foun d to be within +/-3.0ppm.