Microwave spectra have been assigned for the ground state and three excited torsional states of species of cyclopropanecarboxaldehyde with the oxygen atom cis and trans to the cyclopropane ring. Dipole moments obtained by analysis of the Stark effect of the rotational transitions are as follows: cis species: μa = 2.02 ± 0.01 D, μb = 1.86 ± 0.01 D, μc = 0, μ = 2.74 ± 0.01 D; trans species: μa = 3.22 ± 0.01 D, μb = 0, μc = 0.49 ± 0.01 D, μ = 3.26 ± 0.01 D. From relative intensity measurements estimates of the torsional excitation energies of the two species and the cis–trans energy difference were obtained. By analysis of these energy values the first three coefficients in a Fourier series expansion of the torsional potential were deduced to be V1 = − 0.23 ± 0.12 kcal/mole, V2 = 4.39 ± 0.40 kcal/mole, and V3 = 0.28 ± 0.10 kcal/mole.

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Articles you may be interested inThe theoretical prediction of infrared spectra of trans-and cis-hydroxycarbene calculated using full dimensional ab initio potential energy and dipole moment surfaces Microwave spectra have been assigned for the ground state and several excited torsional states of species of cyclopropa~ecarboxylic ac!d fluoride with the oxygen atom cis and trans to the cyclopropane ring. Dipole moments obtamed by analysIs of the Stark effect are as follows: trans species: J.la=3.43±0.03 D, J.lb=0.44± 0.05 D, J.lc=O, J.I=3.46±0.03 Dj cis species: l'a=2.85±0.03 D, J.lb=1.63±0.03 D, J.lc=O, 1'=3.28±0.03 D. By analysis of estimates of the torsional excitation energies of the two species and the cis-trans energv difference, values of the first three coefficients of a Fourier expansion of the torsional potential have bee~ obtained as follows: V 1=-1520±320 cal/mole, V2=5150±700 cal/mole, V,,=990±260 cal/mole. • Observed frequencies are ±O.05 MHz. b In megahertz .