Microwave Spectrum of Ethyl Chloride

The microwave spectrum of ethyl chloride has been investigated and accurate values for the rotational constants B and C for several isotopic species have been obtained. For C2H5Cl35, B=5493.8 Mc, C=4962.3 Mc, and for C2H5Cl37, B=5379.1 Mc and C=4867.1 Mc. Two deuterated species have been studied. For trans CH2DCH2Cl35, B=5098.8 Mc and C=4637.5 Mc. The rotational constants for gauche CH2DCH2Cl35 are B=5297.6 Mc and C=4784.9 Mc. The following model reproduces these constants to within 4 Mc: d C–C=1.5495 A, d C–H=1.101 A, d C–D=1.090 A, ≰ HCH=110° 00′, ≰ CCCl=110° 30′, d C–Cl=1.7785 A. From the structural data obtained for the deuterated ethyl chlorides it has been possible to establish the staggered configuration as the equilibrium configuration. The quadrupole analysis shows that eqQ along the C–Cl bond axis is —70.07 Mc for Cl35 and —55.03 Mc, for Cl37, indicating an ionicity of 25%. The torsional frequency has been estimated to be 236 cm—1 and the barrier height is 3.4 kcal/mole.

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