Nolasco Mariela M, Ribeiro-Claro Paulo J A
Departamento de Química-CICECO, Universidade de Aveiro, 3810-193 Aveiro, Portugal.
Chemphyschem. 2005 Mar;6(3):496-502. doi: 10.1002/cphc.200400423.
C-H...O hydrogen bonds in liquid 2-cyclohexen-1-one are studied to assess the vibrational spectroscopic behavior of the Csp2-H and Csp3-H donors. The presence of a pseudo-isosbestic point in the vC = O region supports the assignment of the two observed bands to two species in equilibrium, considered to be the free and 1:1 associated forms. The values of deltaH degrees =-18.5 +/- 0.6 kJmol(-1) and deltaS degrees = -76 +/- 2 J K(-1) mol(-1) for the dimerization through C-H...O hydrogen bonds were obtained from the dimerization constant at different temperatures. The concentration-dependent intensity of the vCH2 band profile is ascribed to the presence of a blue-shifted band from the hydrogen-bonded Csp3-H group. However, the most surprising result is the absence of concentration- or temperature-dependent intensities in the bands assigned to the stretching modes of the Csp2-H donors.
对液态2-环己烯-1-酮中的C-H...O氢键进行了研究，以评估Csp2-H和Csp3-H供体的振动光谱行为。在vC = O区域存在一个准等吸收点，这支持了将观察到的两个谱带归属于处于平衡状态的两种物质，认为是游离态和1:1缔合态。通过不同温度下的二聚常数，得出通过C-H...O氢键二聚的ΔH° = -18.5 ± 0.6 kJmol⁻¹和ΔS° = -76 ± 2 J K⁻¹ mol⁻¹。vCH2谱带轮廓的浓度依赖性强度归因于氢键连接的Csp3-H基团产生的蓝移谱带的存在。然而，最令人惊讶的结果是，归属于Csp2-H供体伸缩模式的谱带不存在浓度或温度依赖性强度。
