论文部分内容阅读
作为典型的β-二羰基化合物和α,β-烯酮类化合物,乙酰乙酸乙酯在溶液中以多结构存在.在本文中,我们利用飞秒中红外泵浦探测光谱技术,研究了该化合物在重水和环己烷溶液中不同互变异构体的出现在波长6μm(频率范围1600～1800 cm-1)区域的C=O和C=C伸缩振动的振动动力学;并结合稳态红外实验和量子化学计算,分析了这些吸收峰的线型特征.结果表明:在重水中,乙酰乙酸乙酯以酮式存在;而在环己烷中以烯醇式和两种酮式共存.分析稳态红外光谱可以看到,烯醇式结构刚性,其红外光谱线型主要表现为均匀增宽;而酮式的线型则兼具均匀增宽和非均匀增宽.而且,即使在同一种溶剂中,酮式和烯醇式的表观红外光谱线型也有不同.通过泵浦探测实验获得了C=O和C=C伸缩振动衰减动力学和各向异性动力学.重水中酮式的C=O的振动能量弛豫过程比其在环己烷中要快,这可归因于乙酰乙酸乙酯与溶剂发生的分子间氢键作用.此外,烯醇式的C=O伸缩振动和一些振动模式(如COH面内弯曲)之间存在费米共振,直接影响其快速衰减过程,这也是造成其振动衰减动力学不同于酮式的原因.各向异性动力学过程表明,乙酰乙酸乙酯在重水中的转动速度比其在环己烷中要慢一些,与它们不同的溶剂化情况有关.此外,各向异性动力学过程表现出量子拍频现象,在酮式中尤为明显,意味着相关振动模式存在相干激发.
As typical β-dicarbonyl compounds and α, β-enone compounds, ethyl acetoacetate exists as a multi-structure in solution.In this paper, we use femtosecond mid-infrared pump detection spectroscopy to study the compound The vibrational dynamics of C = O and C = C stretching vibration appeared in the region of 6μm wavelength (1600-1800 cm-1) in different heavy and cyclohexane solutions, and combined with steady-state infrared Experiments and quantum chemical calculations, the linear characteristics of these absorption peaks were analyzed.The results showed that ethyl acetoacetate was present as a ketone in heavy water and in enol and two ketones in cyclohexane. Steady-state infrared spectroscopy can be seen that the enol-type structure is rigid, the infrared spectrum of the main linear uniform widened; while the ketones linear both uniform and non-uniform broadening. And, even in the same In solvent, the apparent and infrared spectra of ketone and enol were also different linearly.The kinetics and anisotropy kinetics of C = O and C = C stretching vibration were obtained by the pump detection experiment. The vibration energy relaxation process of C = O is faster than that in cyclohexane, which can be attributed to B. Intermolecular hydrogen bonding between ethyl acetate and solvent.In addition, there is Fermi resonance between the enolase C = O stretching vibration and some vibrational modes (such as COH in-plane bending), which directly affects the rapid decay process, which Also contributed to its kinetics of vibration decay kinetics is different from the keto-type reason.The anisotropic kinetic process shows that ethyl acetoacetate in heavy water than its rotation in cyclohexane to be slower, and their different solvation In addition, the anisotropic kinetic process exhibits quantum beat frequency, which is particularly evident in ketones, implying coherent excitation of related vibrational modes.