MICROWAVE SPECTRUM AND MOLECULAR STRUCTURE OF CYCLOPROPYL CYANIDE
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Date
1974
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University
Abstract
Carbon-carbon bond distances in the cyclopropane ring have been predicted co vary significantly with the electronic nature of substituent $groups.^{1,2}$ Substitution structures give $R_{12} = R_{23} = 1.514$ {\AA} in cyclopropyl $chloride^{3}$, and $R_{12} = 1.464$ and $R_{23} = 1.553$ in 1 1-$difluorocyclopropane.^{4}$ The structure of cyclopropyl cyanide is of interest to determine: (1) whether $R_{23}$ is shorter than 1.514 {\AA}, and (2) whether $R_{12}$ and $R_{23}$ are unequal. The spectra of cyclopropyl $cyanide^{6}$, and the 2-substituted $C^{13}$ isotope have been $reported.^{5}$ The spectrum of the 1-substituted $C^{13}$ isotope has been observed in natural abundance by modulated microwave- and radio frequency-microwave double resonance methods and conventional Stark modulated spectroscopy. Rotational constants for the three species in the rigid rotor approximation are, in MHz: $C^{12}: A = 15 785.821 \pm 0.04, B = 3465.072 \pm 0.006, C = 3286.199 \pm 0.007; C_{1}^{13}: A = 15 614.90 \pm 0.1, B = 3454.776 \pm 0.008, C = 3284.329 \pm 0.006; C_{2}^{13}: A = 15 496.471 \pm 0.04, B = 3421.868 \pm 0.006, C = 3236.838 \pm 0.005$. These results give $R_{12} = 1.529 \pm 0.01$ {\AA} and $R_{23} = 1.500 \pm 0.004$ {\AA}. The direction of change in bond length is in accord with Hoffman’s predictions. The structural parameters are being refined to correct for centrifugal $distortion.^{1}$R. Hoffman, Tetrahedron Letters 33, 2907 (1970). $^{2}$R. E. Penn and J. E. Boggs, J. C. S. Chem. Comm. 11, 666 (1972). $^{3}$R. H. Schwendeman, G. D. Jacobs, and T. H. Krigas, J. Chem. Phys. 40, 1022 (1964). $^{4}$A. T. Perretta and V. W. Laurie, presented at the Symposium on Molecular Structure and Spectroscopy, The Ohio State University, June, 1973. $^{5}$R. Pearson, JR., and V. W. Laurie, ibid. $^{6}$J. P. Friend and B. P. Dailey, J. Chem. Phys. 29, 577 (1958)
Description
Author Institution: Department of Chemistry, Princeton University