时间分辨光谱与DFT结合研究二苯甲酮类化合物的光化学反应

发布时间：2018-04-12 08:09

本文选题：时间分辨光谱 + DFT　；参考：《西北大学》2017年硕士论文

【摘要】：间位取代的二苯甲酮类化合物能发生一些“间位效应”的光化学反应,包括光氧化还原反应、甲基脱质子反应、光取代反应。近些年来,单间位取代二苯甲酮衍生物得到了深入研究。时间分辨光谱技术和密度泛函理论计算相结合的手段是研究的主要方法。单间位取代基团为吸电子基团或者拉电子基团的光化学反应机理已经被研究清楚。然而当间位引入两个取代基团而且一个为吸电子基团一个为供电子基团的情况下,这类二苯甲酮衍生物的光化学反应如何并不清楚?本文选取了 3-氟-3'-羟甲基二苯甲酮(化合物1)和3-氟-3'-甲基二苯甲酮(化合物2)这两个化合物来研究所提出的问题。化合物1和化合物2在间位都引入了两个基团,氟原子为强吸电子基团,羟甲基和甲基都是供电子基团。本文采用时间分辨光谱技术和密度泛函理论相结合的手段对化合物1与化合物2的光物理及光化学过程进行了深入研究。论文的主要内容包括:(1)探索了化合物1的光物理及光化学过程。在乙腈溶液中,化合物1发生了二苯甲酮类化合物的典型光物理过程。在异丙醇溶液中,化合物1发生夺氢反应。在酸性水溶液中,化合物1发生了光氧化还原反应。明晰了化合物1的光氧化还原反应机理,提纯了光解产物并得到了产物的核磁共振谱图。并且发现酸性越强,光氧化还原反应效率越高。通过DFT计算发现,光取代反应过渡态的能垒更高,也就是说相比于光取代反应化合物1更容易发生光氧化还原反应。(2)研究了化合物2的光物理及光化学过程。在乙腈溶液中,化合物2发生了二苯甲酮类化合物的典型光物理过程。在异丙醇溶液中,化合物1发生夺氢反应;在酸性水溶液中,化合物2发生了侧链甲基脱质子反应。明晰了侧链甲基脱质子的反应机理,提纯了光解产物并得到了产物的核磁共振谱图。通过DFT计算发现,光取代应过渡态的能垒更高,意味着甲基脱质子反应比光取代应更容易发生。(3)合成了 3-羟甲基-3'-甲氧基二苯甲酮并采用1H-NMR进行表征。配制3-羟甲基-3'-甲氧基二苯甲酮、3-甲基-3'-甲氧基二苯甲酮的pH0乙腈-水溶液(体积比1:1),进行了纳秒时间分辨拉曼光谱实验,然而并没有发现有“间位效应”的光化学反应发生。
[Abstract]:The m-substituted benzophenone compounds can undergo some photochemical reactions, including photoredox reaction, methyl deprotonation reaction and photosubstitution reaction.In recent years, monosteric substituted benzophenone derivatives have been deeply studied.The method of combining time-resolved spectroscopy with density functional theory is the main research method.The mechanism of photochemical reaction in which the single substituent group is an electron-absorbing group or an electron-pulling group has been studied.However, when two substituents are introduced and one is an electron acceptor, the photochemical reaction of these benzophenone derivatives is not clear.In this paper, we select 3 fluoro-3-methylol benzophenone (compound 1) and 3-fluoro-3-butadiene-methyl benzophenone (compound 2) to study the problems raised.Compound 1 and compound 2 have introduced two groups, fluorine atom is a strong electron-absorbing group, hydroxymethyl group and methyl group are donor groups.In this paper, the photophysical and photochemical processes of compound 1 and compound 2 are studied by means of time-resolved spectroscopy and density functional theory.The main contents of this paper are as follows: (1) the photophysical and photochemical processes of compound 1 are explored.In acetonitrile solution, compound 1 has a typical photophysical process of benzophenone compounds.Compound 1 reacts with hydrogen in isopropanol solution.The photoredox reaction of compound 1 occurred in acidic aqueous solution.The photoredox reaction mechanism of compound 1 was clarified, the photolysis product was purified and the NMR spectra of the product were obtained.It was found that the higher the acidity, the higher the efficiency of photoredox reaction.It is found by DFT calculation that the energy barrier of the transition state of photosubstitution reaction is higher than that of photosubstituted reaction compound 1. The photo-physical and photochemical processes of compound 2 are studied.In acetonitrile solution, compound 2 has a typical photophysical process of benzophenone compounds.In isopropanol solution compound 1 reacts with hydrogen and compound 2 with side chain methyl deprotonation in acidic aqueous solution.The reaction mechanism of side chain methyl deprotonation was clarified, the photolysis products were purified and the NMR spectra of the products were obtained.By DFT calculation, it was found that the energy barrier of the transition state of photosubstitution was higher, which means that the proton removal reaction of methyl was easier than that of photosubstitution. The 3-hydroxymethyl-3-methoxy benzophenone was synthesized and characterized by 1H-NMR.The pH0 acetonitrile-aqueous solution (volume ratio 1: 1) of 3-methyl-3-methoxybenzophenone was prepared. The nanosecond time-resolved Raman spectroscopy was carried out. However, no "inter site effect" photochemical reaction was found.
【学位授予单位】：西北大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O644.19;O625.42

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