反式肉桂酸电喷雾质谱负离子模式脱CO的路径  

Path of the CO loss in negative mode of trans cinnamic acid electrospray ionization mass spectrometry

作　　者：方芳[1] 方舟[1] 孙长海[2] FANG Fang;FANG Zhou;SUN Changhai(School of Clinical Medicine,Jiamusi University,Jiamusi 154003,China;College of Pharmacy,Jiamusi University,Jiamusi 154007,China)

机构地区：[1]佳木斯大学临床医学院,黑龙江佳木斯154003 [2]佳木斯大学药学院,黑龙江佳木斯154007

出　　处：《化学分析计量》2023年第7期87-91,共5页Chemical Analysis And Meterage

基　　金：黑龙江省卫生健康委科研项目(No.2020-326)。

摘　　要：为了从机理上揭示反式肉桂酸在电喷雾质谱负离子模式下脱除CO的路径与特征,运用密度泛函理论方法对反式肉桂酸质谱裂脱除CO过程进行了量子化学计算研究。采用的交换关联泛函/基组为RB3LYP/6-311G,对轻原子所加的弥散函数为S,重原子所加的弥散函数为S与P,所加的极化函数分别为p及d。量子化学计算得到两条反式肉桂酸脱除CO路径,脱除过程均含有4个过渡态与3个中间产物。其中可能性大的脱CO的路径:反式肉桂酸去质子分子先与苄基位碳形成四元内脂环,接着内脂环内发生两次质子迁移生成β-羟基肉桂醛负离子,最后醛基氢转移到邻位碳上,脱去CO生成苯乙酮负离子。可能性大的脱CO路径全程需要的最大能量为356 kJ/mol。由于在电喷雾质谱负离子模式下,反式肉桂酸脱羧所需的能量为172 kJ/mol,因此反式肉桂酸去质子分子的裂解以脱羧优先。反式肉桂酸二级质谱的特征以脱羧为主,即质荷比为103的脱羧碎片离子为一基峰,质荷比为119的脱CO碎片离子的丰度极低。In order to investigate the path and characteristics of CO loss from trans cinnamic acid in the negative mode of electrospray ionization mass spectrometry,a density functional theory was used to study the loss of CO fragmentation process from trans cinnamic acid by theoretical calculation.The exchange-correlation functional/basis set was RB3LYP/6-311G.The dispersion functions added to light atoms was S,and to heavy atoms were S and P.The polarization functions added to light and heavy atoms were p and d,respectively.Two CO elimination paths of trans cinnamic acid were obtained by quantum chemical calculation,which were composed of four transition states and three intermediates.The most likely way of the CO elimination was that the trans cinnamic acid deprotonated molecule first forms a four membered ring of lactone with the benzyl carbon,then the lactones'ring generated twice proton migration to produceβ-hydroxycinnamaldehyde anion,and finally the hydrogen of aldehyde group was transferred to the adjacent carbon to remove CO and the production fragment ion acetophenone anion was formed.The maximum energy required for the whole process of the most possible CO removal path was 356 kJ/mol.Because the energy required for decarboxylation of trans cinnamic acid was 172 kJ/mol in the anion mode electrospray ionization mass spectrometry,the decarboxylation of trans cinnamic acid was preferentially.The decarboxylation was the main characteristic of secondary mass spectrometry,that is,the decarboxylation fragment ion was a basic peak at m/z 103,and the loss CO fragment ion had a very low abundance at m/z 119.

关 键 词：反式肉桂酸 质谱裂解 脱CO 量子化学计算 

分 类 号：O657.6[理学—分析化学]