Haloacetylated compounds: Solvent effects on the O-17 NMR chemical shifts of 1,1,1-trichloro-4-methoxy-3-alken-2-ones

A multi-linear-regression analysis using the Kamlet-Abboud-Taft (KAT) solva tochromic parameters in order to elucidate and quantify the solvent effects on the O-17 chemical shifts of (E)-1,1,1-trichloro-4-methoxy-3-penten-2-on e (1) and (E)-1,1,1-trichloro-4-methoxy-3-methyl-3-buten-2-one (2) are repo rted. The chemical shifts of carbonyl group of the two molecules show simil ar dependencies (in ppm) on the solvent polarity-polarizability (-17 pi*, - 15 pi*) and the solvent hydrogen-bond-donor (HBD) acidities (-7 alpha, -6 a lpha). The influence of the solvent hydrogen-bond-acceptor (HBA) basicities is significant for compound 1 (3 beta) and small for compound 2 (0.7 beta) . The chemical shifts of the methoxy group of the two molecules shows the sam e dependence: tin ppm) on the solvent polarity-polarizability (9 pi*) and t he influence of the solvent hydrogen-bond-donor (HBD) acidities. Note that the solvent hydrogen-bond-acceptor (HBA) basicities were negligible. The da ta obtained from MO calculations suggest that the solvent effects on compou nds 1,2 reflect their conformational structure.