Investigation of CO2/Fluorine Interactions through the Intermolecular Effects on the 1H and 19F Shielding of CH3F and CHF3 at Various Temperatures and Pressures

The nuclear shielding for both the 1 H and 19 F nuclei of CH 3 F and CHF 3 was investigated as a function of pressure and temperature. The density region investigated extended from low, gaslike conditions to study pairwise intermolecular interactions to high, liquidlike densities to study multibody effects on nuclear shielding. The temperature range was from 30 to 150 °C. Neat samples of CH 3 F and CHF 3, along with CO 2 mixtures of these fluorocarbons, were investigated by 1 H and 19 F high-pressure NMR. Molecular dynamics simulations were undertaken to describe the pair-distribution functions for both the neat samples and mixtures to aid in the interpretation of the 1 H and 19 F nuclear shielding determined from high-pressure NMR. The NMR spectra of the neat fluoromethanes and their CO 2 mixtures suggest that there are no distinct or specific interactions between the fluoromethanes and CO 2 and that as the temperature increases the multibody effects play less of a role in nuclear shielding.