Dipole moments of seven refrigerants

Abstract

This paper reports that Dielectric constant measurements have been performed on seven refrigerants in the gaseous state over the range 305-415 K in order to determine their dipole moments. Four of the refrigerants have temperature-independent moments: R123, [mu] -= 1.358 [plus minus] 0.019 D; R141b, [mu] = 2.014 [plus minus] 0.018 D; R22, [mu] = 1.458 [plus minus] 0.003 D; and R32, [mu] = 1.978 [plus minus] 0.007 D. Two refrigerants have conformer-dependent moments, making their time-averaged moments temperature dependent: R114, with a moment ranging from 0.668 [plus minus] 0.001 D at 308 K to 0.699 [plus minus] 0.001 D at 410 K; and E134, where the moment ranges from 1.739 [plus minus] 0.002 D at 309 K to 1.840 [plus minus] 0.001 D at 410 K. One refrigerant, R123a, has a moment that in principle could be temperature-dependent but in fact is temperature-independent; its value is [mu] = 1.302 [plus minus] 0.007 D. Accurate determination of a molecule's temperature-dependent dipole moment requires an independent determination of its electronic polarizability; this determination has been made from index of refraction measurements. Where possible, the present results are compared with earlier determinations of dipole moments.