1H, 13C and 19F nuclear magnetic shielding and spin–spin coupling in gaseous trifluoromethane

Trifluoromethane (CHF3) has been studied using 1H, 13C and 19F NMR spectra in the gas phase at 300 K. For the first time all the spin–spin couplings and 13C shielding of CHF3 were measured as functions of density. After extrapolation to the zero-density limit the appropriate shielding (1H, 13C and 19F) and spin–spin coupling parameters of an isolated CHF3 molecule were obtained. 19F NMR measurements were extended on the 12CDF3 and 13CHF3 molecules present in samples at the natural abundance of deuterium and carbon-13 isotopes, they permitted the determination of isotope effects in 19F shielding of studied molecules. As shown the new NMR parameters are determined with better accuracy than older measurements and therefore they are more suitable for comparison with the results of ab initio calculations. q 2005 Elsevier B.V. All rights reserved