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Microwave spectroscopic studies of chloryl fluoride and acetaldehyde-D1 Parent, Charles Robert

Abstract

The microwave spectra of three isotopic species of chloryl fluoride, ³⁵Cl¹⁶O₂F, ³⁷Cl¹⁶O₂F, and ³⁵Cl¹⁶O¹⁸OF, have been measured and the transitions fit to Watson's nonrigid rotor reduced Hamiltonian. The resulting rotational constants have allowed the calculation of a molecular structure that features an anomalously long Cl-F bond and unusually short Cl-O bonds. The nuclear quadrupole coupling constants and electric dipole moment have also been determined and both suggest the withdrawal of considerable electron density from the CIO₂ moiety along the Cl-F bond. The molecular structure and ionic character of the Cl-F bond are consistent with a modification of the multicentered molecular orbital bonding theory proposed by Lipscomb and expanded by Spratley and Pimentel. Chloryl fluoride may profitably be viewed as a molecule created by the formation of a bond between a fluorine atom and a stable paramagnetic chlorine dioxide molecule. Qualitatively the anomalously long Cl-F bond results from overlap of a fluorine 2p atomic orbital with a lobe of the highest singly occupied antibonding molecular orbital of CIO₂. The significant contraction of the CI-O bond in CIO₂F, compared to the bond in CIO₂, suggests that there is considerable electron withdrawal from this CIO₂ antibonding orbital. Similar bonding pictures are used to correlate the anomalous structures of NO₂F, NOF, NSF, O₂F₂, and S₂F₂. The rotational constants and barrier to internal rotation of the CH₃CDO isotopic species of acetaldehyde have been determined. The barrier is in good agreement with barrier heights of other isotopic species previously measured, and the rotational constants are consistent with the recent zero-point average structure reported by Iijima and Tsuchiya. [See Thesis for Diagram]

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