GROUP CONTRIBUTION-ADDITIVITY AND QUANTUM-MECHANICAL MODELS FOR PREDICTING THE MOLAR REFRACTIONS, INDEXES OF REFRACTION, AND BOILING POINTSOF FLUOROCHEMICALS

Group contribution-additivity (GCA) and quantum mechanical (QM) models for estimating the molar refractions of fluorochemicals are proposed. The GCA model was developed using experimental refractive indices and densities, and the Lorentz-Lorenz electromagnetic correlation. The QM model was developed using the distortion polarizability (alpha>) term obtained from quantum mechanical calculations based on the PM3 Hamilt onian. The GCA model provides molar refractive contributions for 23 he terogeneous groups and atoms (e.g., R(F), R(H), C, N, O, F, Cl, Br, I, C=O, NH2, OH, CH=C, CH=CH, CH2=C, CH=CF2, CF=CF2) and yields an absol ute average error of less than 2% (n=100). The QM model, on the other hand, offers unlimited groups but requires knowledge of the alpha desc riptor. Methods for acquiring alpha are provided. Both models have bee n successfully applied to the predictions of refractive index (n(D)) a nd the normal boiling point (T-b) of fluorochemicals, with average err ors of less than 1% and 6%, respectively. The higher method error obse rved in the T-b model is attributed to errors introduced by T-b measur ements at pressures slightly below 760 mmHg. The T-b model, nonetheles s, provides accurate predictions of boiling point in the range between 30 and 230 degrees C.