Durig James R, Zhu Xiaodong, Guirgis Gamil A
Department of Chemistry, University of Missouri-Kansas City, Kansas City, MO 64110-2499, USA.
Spectrochim Acta A Mol Biomol Spectrosc. 2004 Mar;60(4):829-41. doi: 10.1016/S1386-1425(03)00308-1.
The infrared spectra (3500-50 cm-1) of gas and solid and the Raman spectrum (3500-50 cm-1) of liquid 2-fluorobutane, CH3CHFCH2CH3, have been recorded. Variable temperature studies over the range -105 to -150 degrees C of the infrared spectra (3500-400 cm-1) of the sample dissolved in liquid krypton have also been recorded. By utilizing the relative intensities of six conformer pairs each for both Me-trans/F-trans and Me-trans/H-trans, the Me-trans conformer is found to be the lowest energy form with an enthalpy difference to the F-trans conformer of 102 +/- 10 cm-1 ( 1.21+/- 0.12 kJmol-1) whereas the H-trans conformer is the highest energy form with an enthalpy difference of 208 +/- 21 cm-1 ( 2.49 +/- 0.25 kJmol-1) higher than the Me-trans form. At ambient temperature, it is estimated that there is 50 +/- 2% of the Me-trans form, 31 +/- 1% of the F-trans form, and 19 +/- 1% of the H-trans conformer present. Equilibrium geometries and total energies of the three conformers have been determined by ab initio calculations with full electron correlation by the perturbation method to second order using a number of basis sets. A complete vibrational assignment is proposed for the Me-trans conformer and many of the fundamentals have been identified for the other two forms based on the force constants, relative infrared and Raman intensities, and depolarization ratios obtained from MP2/6-31Gd ab initio calculations. The spectroscopic and theoretical results are compared to the corresponding properties for some similar molecules.
已记录了气态和固态 2-氟丁烷（CH3CHFCH2CH3）的红外光谱（3500 - 50 cm-1）以及液态 2-氟丁烷的拉曼光谱（3500 - 50 cm-1）。还记录了溶解在液态氪中的样品在 -105 至 -150 摄氏度范围内的红外光谱（3500 - 400 cm-1）的变温研究。通过利用 Me-反式/F-反式和 Me-反式/H-反式各自的六对构象异构体的相对强度，发现 Me-反式构象异构体是能量最低的形式，与 F-反式构象异构体的焓差为 102±10 cm-1（1.21±0.12 kJmol-1），而 H-反式构象异构体是能量最高的形式，比 Me-反式形式的焓差高 208±21 cm-1（2.49±0.25 kJmol-1）。在环境温度下，估计存在 50±2%的 Me-反式形式、31±1%的 F-反式形式和 19±1%的 H-反式构象异构体。使用多种基组，通过二阶微扰法进行全电子相关的从头算计算，确定了三种构象异构体的平衡几何结构和总能量。基于从 MP2/6 - 31Gd 从头算计算获得的力常数、相对红外和拉曼强度以及去极化率，为 Me-反式构象异构体提出了完整的振动归属，并为其他两种形式确定了许多基频。将光谱和理论结果与一些类似分子的相应性质进行了比较。
