Deuterium Isotope Effects on Nuclear Shielding. Directional Effects and Nonadditivity in Acyl Derivatives

Article abstract of DOI:10.1021/ja00264a011

Deuterium isotope effects on the 19F and 13C nuclear shieldings have been investigated in acyl derivatives.A nonadditivity of the ³ΔF(D) of acetyl fluoride has been experimentally established and related primarily to nonuniform rotamer distributions of the mono- and dideuteriated isotopomers.The ³ΔF(D)'s show furthermore a distinct orientational dependence.The isotope effects for the configurations where the nuclei in question are in a trans position are positive and those in which they are gauche are negative.The ²ΔCO(D)'s are negative and additive in all the investigated cases.The observed isotope effects are discussed in general in terms of substituent and vibrational effects.