缩氨基脲类和缩氨基硫脲类衍生物的质谱研究

THE STUDY OF MASS SPECTROMETRY ON SEMICARBAZONE AND THIOSEMICARBAZONE DERIVATIVES

用高、低分辨质谱,重氢标记和亚稳跃迁研究了取代缩氨基脲和缩氨基硫脲类衍生物的质谱碎裂行为.结果表明,分子离子的丰度、基峰离子的生成方式以及碎片离子的种类、丰度和数量主要取决于取代基R的诱导效应和共轭效应的综合影响.质谱的碎裂特征是:(1)当R为N(CH),OH时,分子的电子云分布均匀,共轭性好,基峰为分子离子峰.(2)当R为H,F时,缩氨基脲8-N位缺电子最甚,导致9-N和10-C之间键的断裂,生成的高稳定离子p-RCHCH=N=NH为基峰.但缩氨基硫脲类衍生物,因电子云分布均匀,基峰仍为分子离子峰.(3)当R为Br,NO时,由于诱导效应强烈,分子的电子云分布不均匀,12-O(或12-S)成为缺电子最甚的原子,8-N和9-N之间键断裂、重排而生成的离子[HNC(NH)-XH](X=O,S)为基峰.(4)11-NH基团重排到苯环3,5位上,生成离子(o-RCHNH)只有当R为H时,反应最易发生.R为强给电子基或强吸电子基,对反应都不利.

The MS fragmentation behaviors of semicarbazone and thiosemicarbazone(1)with different polar group R under electron impact were investigated in detail with the aid of exact mass measurements,metastable ion measurement of MS and their corresponding deuterium labelling compounds.The results showed the abundance of molecular ions,the way of forming base peak and the kinds,abundance as well as numbers of fragments are also mainly depend upon the induction and conjugation effect of group R.The cha-racterestics of MS fragmentation are as follows:(1)When R=N(CH),OH,the ion of base peak is the molecular ion itself.Since the electronic cloud in the molecule is distri buted evenly so that the molecule is well conjugated.(2)When R=H,F,the electronic density at site of 8-N in the semicarbazone is very low so it induces the cleavage of the bond between 9-N and 10-C to produce a high stable ion RCHOH=N=NH as a base peak.Subsequently,the hydrogen on the 7-C rearrange to 12-O to induce the cleavage of the bond between 8-N and 9-N producing a rearrangement ion(p-RCHC≡N)as a sub-base peak.However,the distribution of electronic cloud is still even and ion of base peak is molecular ion itself for the thiosemicarbazone when R=H,F.(3)If R=Br,NO,the distribution of electronic cloud in the molecule is uneven and electronic den-sity around 12-O is lowest in the molecule that makes the hydrogen on 7-C rearranging to 12-O to induce the cleavage of the bond between 8-N and 9-N producing a rearrange-ment ion[NHC(NH)=XH](X=O,S)as a base peak.(4)Rearranging group 11-NHto sites 3 and 5 of the benzene ring to produce the ion o-RCHNHoccurred more readily only when R=H.If R is either electronic donator or acceptor the reaction is unfavorable.