Morpholine sulfur trifluoride: Vibrational spectra, conformational properties and crystal structure

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• 作者：Andrea Flores Antognini^a ; Norma L. Robles^a ; ^{lisrobles@fbqf.unt.edu.ar} ; Edgardo H. Cutin^a ; ^{cutin@fbqf.unt.edu.ar} ; Eduard Bernhardt^b ; Markus Hirschberg^b ; Xiaoqing Zeng^b ; Helge Willner^b ; Heinz Oberhammer^c
• 关键词：Morph-SF3 ; Matrix IR spectra ; Low temperature Raman spectra ; X-ray crystallography ; Quantum chemical calculations
• 刊名：Journal of Fluorine Chemistry
• 出版年：2012
• 出版时间：December, 2012
• 年：2012
• 卷：144
• 期：Complete
• 页码：59-64
• 全文大小：471 K

文摘

Analysis of the vibrational spectra and quantum chemical calculations for morpholine sulfur trifluoride, SF₃N(CH₂CH₂)₂O, demonstrate that the morpholine ring possesses chair conformation and occupies an equatorial position of the trigonal bipyramidal SF₃ group. The compound exists in the gas phase as a mixture of two conformers. The conformer with the SF₃ group in equatorial orientation relative to the six-membered morpholine ring is slightly more stable than the axial conformer and the equilibrium is surprisingly temperature independent. MP2 and B3LYP calculations with cc-pVTZ basis sets predict free energy differences ¦¤G¡ã = G¡ã_ax ? G¡ã_eq of +0.18 and +0.40 kcal/mol, respectively. At temperatures below 12 ¡ãC the title compound crystallizes and the structure of the equatorial conformer, which is the only form present in the crystal, was determined by X-ray diffraction. At 131(1) K a phase transition occurs and the low and high temperature forms were studied at 100 and 150 K, respectively.