The effect of Lewis bases on the (13)c NMR of iodoalkynes.
In Lewis-basic solvents, alkynyl carbons bonded to iodine have chemical shifts approximately 12-15 ppm higher in frequency than the corresponding shifts in CDCl3. We offer computational evidence that this solvent effect comes directly from polarization of the iodoalkyne triple bond. Hartree-Fock and Density Functional Theory calculations reproduce the change in chemical shift for a gas-phase complex between the iodoalkyne and dimethyl sulfoxide as Lewis base. The amount of spin-orbit coupling from the adjacent iodine does not change appreciably in the complex, according to the calculations.
Rege
Pankaj D
PD
Department of Chemistry, State University of New York, Stony Brook, New York 11794-3400, USA.
Malkina
Olga L
OL
Goroff
Nancy S
NS