CH bonds with a Positive Dipole Gradient Can Form Blue-Shifting Hydrogen Bonds: The Complex of Halothane with Methyl Fluoride
✍ Scribed by Bart Michielsen; Wouter A. Herrebout; Benjamin J. van der Veken
- Publisher
- John Wiley and Sons
- Year
- 2008
- Tongue
- English
- Weight
- 359 KB
- Volume
- 9
- Category
- Article
- ISSN
- 1439-4235
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✦ Synopsis
Abstract
The complex of halothane (CF~3~CBrClH) with ([D~3~])methyl fluoride is investigated theoretically by means of ab initio calculations at the MP2/6‐311++G(d,p) level and experimentally by infrared spectroscopy of solutions in liquid krypton. The complexation energy is calculated to be −12.5 kJ mol^−1^. The dipole moment of halothane monomer as a function of the CH stretching coordinate is calculated with different methodologies and the value of (∂μ/∂Q~1~)~0~ is found to be positive. In the spectra, formation of a 1:1 complex is observed. The standard complexation enthalpy is measured to be −8.4(2) kJ mol^−1^. The CH stretching vibration of halothane shows a blueshift of +15.4 cm^−1^ on complexation, and its infrared intensity ratio ε~complex~/ε~monomer~ is found to be 1.39(7). The frequency shift is analyzed by a Morokuma analysis, and the infrared intensities are rationalized by using a model which includes the mechanical and electrical anharmonicity of the CH stretching vibration.