# CONFORMATION BARRIERS TO INTERNAL ROTATION IN CYCLOPROPANECARBONYL FLUORIDE

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 Title: CONFORMATION BARRIERS TO INTERNAL ROTATION IN CYCLOPROPANECARBONYL FLUORIDE Creators: Durig, J. R.; Bist, H. D.; Little, T. S. Issue Date: 1982 Publisher: Ohio State University Abstract: The infrared and Raman spectra have been recorded for the gaseous and solid states of cyclopropanecarbonyl fluoride, $c-C_{3}H_{6}CFO$. The asymmetric torsion for the conformer which has the carbonyl group cis to the cyclopropane ring has been observed at $88.5 cm^{-1}$ in the far infrared spectrum of the gas with five accompanying hot bands and the corresponding torsion of the trans conformer was observed at $90.9 cm^{-1}$ with two additional hot bands occurring at $90.6 and 90.2 cm^{-1}$, From these data the potential function for internal rotation of the asymmetric top has been determined and the following potential constants have been evaluated: $V_{1}= -618 \pm 6, V_{2}= -1970 \pm 27, V_{a}=399 \pm 6$ and $V_{4}= -48 \pm 10 cm^{-1}$. It has been determined that the cis conformer is the predominant form at ambient temperature and the enthalpy difference between the cis and the trans conformers is $220 cm^{-1}$ (629 cal/mol) for the vapor. The calculated trans-cis barrier is $1948 cm^{-1}$ (5.57 kcal/mol) and the cis-trans barrier is $2168 cm^{-1}$ (6.20kcal/mol). From a temperature study of the Raman spectrum of the liquid an energy difference of $92 \pm 20 cm^{-1}$ (263cal/mol) has been determined which compares as well as expected with the value for the vapor. These results are compared to similar quantities in some related molecules. URI: http://hdl.handle.net/1811/28958 Other Identifiers: 1982-WF'-4