The microwave spectrum of acrolein has been studied in the 19–37 kmc region. A series of R-type transitions was identified for the ground and three excited torsional states of the s-trans isomer and these spectra were successfully fitted in the rigid rotor approximation. Using the ground state moments and additional electron diffraction data a reasonable though not unique structure has been obtained. The torsional frequency was found to be 200±50 cm—1 from relative intensity measurements, and a lower limit of about 2300 cal was estimated for the barrier hindering trans-cis conversion. The dipole moment for the ground state was found to be 3.11±0.04 d, oriented about 14° from the carbonyl group. The results obtained and the absence of a strong s-cis spectrum establish the s-trans isomer as the predominant form.

The microwave spectrum of ethyl bromide has been investigated and accurate values for the rotational constants Band C and the asymmetry parameter b have been obtained. For C2H.Br 79 B=3804.5 Mc, C=3522.5 Mc, b= -0.00487949 and for C2H.Br 81 B=3781.5 Mc, C=3503.0 Me, and b= -0.00522977. The following model reproduces these constants to within 2 Mc: C-C 1.5495 A, C-H 1.110 A, C-Br 1.9400 A 1:C-C-H 110°00', 1:C-C-Br 110°30'. Analysis of the quadrupole hyperfine structure indicates that eqQ along the C-Br bond axis is 537.5 Mc for C2H,Br 79 and 450.9 Mc for C2H.Br 81 • Two transitionshave not been able to be fitted by first-order or second-order nondegenerate quadrupole theory. The torsional frequency is estimated to be 202 cm-1 and the barrier height is 2.80 kcal/mole.

The microwave spectrum of ethyl chloride has been investigated and accurate values for the rotational constants Band C for several isotopic species have been obtained. For C 2 H.Cp·, B=5493.8 Mc, C=4962.3 Mc, and for C2H sC137, 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 CH 2 DCH 2 Cl35 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', <}::CCCI= 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 Cl3S and -55.03 Mc, for CP7, 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.

No abstract

No abstract