Empirical Correlation between the Molecular Electric Field Gradients and the Average Molecular Polarizabilities of some Halogen Compounds

Abstract

A NUCLEAR quadrupole resonance signal¹ is split into two components by electrostatic fields² with up to maximum field strengths of 50 kV/cm. The separation between the two components is a linear function² of the polarizability of the molecular species under investigation. The aim of this communication is to demonstrate the general validity of this particular relationship² which is in fact independent of any restricting experimental conditions, for example application of an electrostatic field (Stark effect²). Although there are relatively few compounds for which both the nuclear quadrupole resonance and molecular polarizability data are available, the general validity of the correlation between the molecular polarizability and nuclear quadrupole resonance parameters, such as the molecular electric field gradients q_zz, can be demonstrated conclusively in the series of the homologous compounds CH₃C1, CH₂Cl₂ and CHCl₃. The relevant experimental data^3–7 are shown in Table 1 and illustrated in Fig. 1.