Chlorine nuclear quadrupole resonance study on 1,3-dichloroacetone: dimorphism and temperature dependence of the 35Cl-NQR

Abstract

Solid 1,3-dichloroacetone, CH 2ClCOCH 2Cl, is dimorphic. The 35Cl-NQR spectra and the X-ray powder patterns are given for both modifications. Phase I shows a single chlorine resonance, whereas phase II (considered to be metastable) gives a four line spectrum. The implications from the NQR spectra with respect to the crystal structures of the two modifications are discussed. The temperature dependence of the 35Cl-NQR frequencies is described by the relationships v I = 35.9989 − 16.02 · 10 −1 · T − 7.350 · 10 −6 · T 2 + 8.57 · T −1 ( v in MHz, T in K) (Phase I in the range 77 K ⩽ T ⩽ 318 K), and by v 1 II = 36.2968 + 8.19 · 10 −4 · T − 11.409 · 10 −6 · T 2 + 13.39 · T −1, v 2 II = 36.1459 + 5.93 · 10 −4 · T − 10.447 · 10 −6 · T 2 + 12.27 · T −1, v 3 II = 36.0691 + 1.55 · 10 −4 · T − 9.537 · 10 −6 · T 2 + 11.72 · T −1, v 4 II = 35.8244 + 4.42 · 10 −4 · T − 13.502 · 10 −6 · T 2 + 17.22 · T −1, (Phase II in the range 77 K ⩽ T ⩽ 308 K).