Variation of nuclear magnetic shielding with intermolecular interactions and rovibrational motion. VII. 19F in CF2H2, CF2HCl, CFHCl2, CF2Cl2, and CFCl3

Abstract

Variable density and temperature studies of fluorine-19 nuclear magnetic resonance spectra in the title molecules reveal the effects of intermolecular interactions, quantitatively expressed as a second virial coefficient of nuclear shielding σ1(T) and the effects of rovibrational averaging, expressed in terms of the temperature dependence of shielding in the molecules in the zero-pressure limit σ0(T). The quantities are reported as quadratic functions of temperature and compared with those of other molecules. In the four series of molecules: (a) CH3F, CF2H2, CF3H, CF4; (b) CFC13, CF2C12, CF3Cl, CF4; (c) CF2Cl2, CF2HCl, CF2H2; and (d) CFCl3, CFHCl2, CFH2Cl, CFH3, ‖dσ0/dT‖ has been found to decrease with H substitution and increase with Cl substitution. Gas-to-liquid shifts are also reported.