The Microwave Spectra, Structure, Dipole Moment, and Chlorine Nuclear Quadrupole Coupling Constants of Methylene Chloride

Abstract

The microwave spectra of CH2Cl235, CH2Cl35Cl37, CH2Cl237, CDHCl235, CDHCl35Cl37, CD2Cl235, and CD2Cl35Cl37 have been examined and effective moments of inertia have been determined for these seven isotopic species. From these data the effective bond distances and angles were determined as C–Cl distance=1.7724±0.0005A, Cl–C–Cl angle=111°47′±1′, C–H distance=1.068±0.005A (average of all species), or 1.082A (extrapolated to infinite hydrogen mass), and H–C–H angle=112°0′±20′ (average of all species) or 112°58′ (extrapolated to infinite hydrogen mass). The best value for the dipole moment of methylene chloride was found from the Stark splitting to be 1.62±0.02×10−18 esu. The chlorine nuclear quadrupole coupling constants were also determined and their relationship to the structure is discussed.

Influence of Vibrations on Molecular Structure Determinations. I. General Formulation of Vibration—Rotation Interactions

“…(9). Since a 1 is between -2 arid -4 for almost all diatomic molecules~2 3 the aru1armonic term predominates; however,…”

Halogen Nuclear Quadrupole Coupling Constants in Non-axially symmetric Molecules; Ab initio Calculations, which Include Correlation, Compared with Experiment

“…In order to determine the 'effective atomic quadrupole coupling constants' for each halogen, we scale the values used by the slope of the correlation line. This gives the values, CI -84.63 (33), Br +314.48 (80), I -724.74(310) mb, where the errors are based on the SE of the regression slope. The % changes for the nuclei are thus CI +3.6, Br -5.0 and I -5.9% respectively.…”

“…Dichloromethane is a typical case [33]; the calculated rotation constants (A, B, C) in MHz are shown in Table 3. These are typical levels of agreement between the equilibrium geometriy rotation constants (for the most common isotopes) and the substitution structure in MW spectroscopy.…”

Theoretical Investigation on the Nuclear Quadrupole Interaction of CH3Cl, CH2Cl2 and CHCl3

“…This influ ence of the surrounding molecules, here called the solid state effect, leads to a decrease of the E FG at the chlorine nucleus. This solid state effect is explained qualitatively by the change of the C l-C distance on going from the gas phase [16][17][18] to the solid state, and furthermore by intermolecular C l-H bonds in the crystal [12,19],…”