Ab initio 19F NMR chemical shifts calculations for halogenated ethanes and propanes

Ab initio GIAO [1] F-19 NMR chemical shift calculations were carried out on halogenated ethanes and propanes (CF3-CXYZ, CF3CF2-CXYZ, CH3CF2-CXYZ: X, Y, Z; H, Cl or F), considering their all rotamers. As for CF3-CXYZ, the HF/6-31G(d)//HF/6-31G(d) level gave a better correlation between the observed and calculated values than the B3LYP/6-31G(d)//B3LYP/6-31G(d) level. The calculated F-19 NMR chemical shifts for CF3CF2-CXYZ and CH3CF2-CXYZ also showed fairly good linear relationships with the observed values. The HF/6-31G(d) level of theory is found to be cost-effective and sufficient to assign or predict F-19 NMR chemical shifts for small aliphatic halogenated compounds. (C) 1999 Elsevier Science S.A. All rights reserved.