ROLE OF POLAR FACTORS IN COLLISION COMPLEX MODELS FOR SOLVENT AND CONCENTRATION DEPENDENCE OF NUCLEAR MAGNETIC RESONANCE PARAMETERS

A detailed experimental study of the nmr parameters of α-chloroacrylonitrile (α-CAN) has been carried out in seven solvents over the entire concentration range. The results have been interpreted on the basis of a collision complex model using least-squares methods to determine the association constants and nmr parameters for each postulated species. Parameter values appear reasonable and account for the observed parallel behavior of shifts and couplings in α-CAN. It has been shown that the influence of dielectric constant on the nmr parameters can be related to the influence of the solvent dipolar cohesive energy in the equilibrium constant of the collision complex model. The effect of reaction electric fields on chemical shifts has been introduced as a virial-type expression involving a Stockmayer intermolecular potential. This procedure accounts for previously observed nonlinearity in the dependence of the shift on an Onsager-type reaction field.