Ab initio chemical shifts calculations for halogenated ethanes and propanes

Ab initio GIAO [1] 19 F NMR chemical shift calculations were carried out on halogenated ethanes and propanes (CF 3 –CXYZ, CF 3 CF 2 –CXYZ, CH 3 CF 2 –CXYZ: X, Y, Z; H, Cl or F), considering their all rotamers. As for CF 3 –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 19 F NMR chemical shifts for CF 3 CF 2 –CXYZ and CH 3 CF 2 –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 19 F NMR chemical shifts for small aliphatic halogenated compounds.