C_（60）与某些有机小分子的气相离子－分子反应

Ｃ_（６０）与某些有机小分子的气相离子－分子反应中国科学院长春应化所刘淑莹教授等发现气相Ｃ６。在化学电离质谱中分别与３种氯代甲烷和４种氯代乙烷的分子离子及其碎片离子发生气相离子－分子反应，观察到Ｃ。０的几十种气相加合离子（其中大多数为含氯原子的）。通?..     

镍离子与直链烷烃分子气相反应的飞行时间质谱

金属离子与有机分予的气相反应是近年来气相化学研究的热声、并已成为金属有机化学的一个重要领域［‘－‘］．目前，离子回旋共振＊；二次离子质谱门和离子束技术问等方法已被广泛应用于金属离子与有机分子的气相反应研究，并已取得许多优秀的结果．在本文中，我们使用一种非常简单的方法，即激光解离固体金属产生的金属离子与流动的有机分子气体反应的方法，并使用简单的飞行时间质谱仪来研究金属离子与直链烷烃分子的气相反应．1实验所有的实验都是在配有飞行时间质谱仪的真空腔内进行．一个长4m－m，内径2。l的石英玻璃管道平行放置于电…     

甲醇缩合生成二甲醚的质谱和量子化学研究

利用质谱分析结果结合量子化学abinitio方法,研究甲醇缩合脱水的反应过程.研究表明,在气相中,甲醇分子主要以二聚体和多聚体的形式存在,据此提出甲醇脱水反应的原始反应物是甲醇二聚体,而不是单个甲醇分子.研究了气相甲醇二聚体、过渡态的能量和结构、甲醇脱水生成二甲醚反应的可能反应途径和反应势垒,对甲醇缩合脱水生成二甲醚的反应性及其影响因素作了讨论.     

四氢咪唑取代亚甲基β—二酮质谱碎裂机理的理论研究

理论计算非常适用于气相离子化学研究[1，2]，它与质谱实验相结合可以识别许多非常规的和以往所不知道的自由基离子，也可以提供反应能和机理方面的信息，有助于探讨可能的异构化过程和不同异构体结构的相对稳定性．离子／中性复合物（离子和中性碎片通过静电引力结合在一起）[3]作为有机离子质谱单分子碎裂的重要中间体已被越来越多的理论和实验结果所证实[3，4]．串联质谱低能碰撞诱导解离和同位素标记技术的实验结果表明[5]：四氢咪唑取代亚甲基β-二酮分子结构中氮原子上氢表现出不同活性，其气相单分子碎裂经历了离子／中性复合物的中…     

气相中铜催化的脱羧碘化反应

提供了一种通过电喷雾电离质谱在气相中对一类有机铜配体复合物的合成方法.通过碰撞诱导解离和分子-离子反应,在离子阱质量分析器中完成了气相中铜催化的脱羧碘化反应.羧酸（RCOOH）作为反应物最终通过碰撞诱导解离技术和分子-离子反应转化为碘代烃（RI）.在整个反应过程中,观察到了铜的价态变化,由此也对羧酸的脱羧碘化反应的反应机理进行了解释.同时,不同的羧酸和双氮配体也适用于该反应体系.该方法检测了一类有机铜复合物的气相反应活性,并对液相中铜催化的脱羧碘化反应的反应机理研究提供了重要信息.     

应用MALDI-FTICRMS技术研究气相中含钨系列离子簇

以Keggin型磷钨酸为原料, 2,5-二羟基苯乙酮(DHAP)和2,4,6-三羟基苯乙酮(THAP)为基质, 使用基质辅助激光解吸/电离-傅里叶变换离子回旋共振质谱(MALDI-FTICRMS)技术研究气相中金属相关簇的稳定性及气相离子-分子反应. 在气相中获得不同系列的-1价含钨离子簇, 准确确定各系列离子簇的组成及Magic Numbers物种, 并发现基质与钨相互作用生成有机-无机杂化离子簇系列. 结果表明, MALDI-FTICRMS技术适用于研究气相中团簇离子的稳定性及气相离子-分子反应.     

气相离子对SN2反应LiY+CH3Cl→CH3Y+LiCl(Y=F～I) 的密度泛函理论研究

在双分子亲核取代反应中,常见的亲核试剂是各种阴离子或中性分子.当亲核试剂是中性的离子化合物时,就有可能发生离子对SN2反应.尽管关于这种离子对SN2反应已有一些实验结果[1,2],但相应的理论研究报道仅限于少量的对称取代反应[3].本文采用密度泛函理论,在B3LYP/6-311+G(d,p)水平上对离子对SN2反应LiY+CH3Cl→CH3Y+LiCl(Y=F,Cl,Br,I)进行了计算研究,并与相应的阴离子SN2反应Y-+CH3Cl→CH3Y+Cl-(Y=F,Cl,Br,I)进行了比较,得到了一些有价值的结论,这些结论能帮助我们更深入地了解离子对SN2反应所遵循的规律.     

2—羟基—4—邻苯二甲酰亚胺基丁酸的氢迁移反应

在甲烷为反应气的化学电离质谱条件下，质子化的２－羟基－４－邻苯二甲酰亚胺基丁酸的单分子质谱碎裂产生了ｍ／ｚ１４８的碎片离子，表明其碎裂过程发生了氢迁移反应，ＡＭ在分子轨道的理论计算结果为可能的质子化位置提供了理论依据；建立在氘代同位素标记和碰撞诱导解离实验的基础上，我们提出此离子的形成可能同时存在单氢迁移和双氢迁移，一些质谱图中的物征碎片中离子为可能的ＭｃＬａｆｆｅｒｔｙ重排和离子／中性（碎片）复     

过渡金属离子与乙腈团簇的反应

用激光溅射-分子束技术,研究了几种过渡金属离子与乙腈团簇分子的气相化 学反应,根据反射式飞行时间质谱检测的结果,不同的过渡金属离子可与乙腈分子 形成不同尺寸的团簇离子产物,其中Ti~+,V~+,Cr~+与乙腈反应的活泼性强于 Cu~+,Fe~+与乙腈反应的活泼性。分析过渡金属离子Ti~+,V~+,Cr~+与乙腈反应 所生成团簇离子的强度分布,发现它们都在n = 2和n = 3之间形成明显的强度间隙 。     

氯苯类污染物在高层大气环境中形成的可能性

简要地总结了大气离子与自由基反应的研究进展和以氯苯为目标产物的气相离子-分子反应的质谱研究。根据大气层状结构图、高层大气的特点以及相关的研究结果,提出了氯苯类污染物的形成不排除是大气化学反应尤其是离子反应产物的观点。对进一步研究大气中氯苯类污染物的生成机制和控制具有重要意义。     

Study on the reactions of pyridine with fluorine-containing compounds in the gas-phase by electron impact/Fourier transfer ion cyclotron resonance mass spectrometry

The gas-phase ion-molecule reactions of pyridine and fluorine-containing compounds have been studied by the electron impact/Fourier transfer ion cyclotron resonance mass spectrometry (EI/FTICRMS). Comparing the reaction of the standard sample perfluorotributylamine (PFTBA), in the case of 3-oxa-5-iodo-octafluoropentylsulfonyl azide (ICF₂CF₂OCF₂CF₂SO₂N₃), a series of addition-elimination products and loss 28 from the expected adducts were obtained. Possible reaction mechanism was discussed, which was consistent with the results obtained in the condensed phase. These results demonstrated that EI/FTICRMS is a complementary technique for study of the organic reactions.     

Study on the reactions of pyridine with fluorine-containing compounds in the gas phase by electron impact/Fourier transfer ion cyclotron resonance mass spectrometry

The gas-phase ion-molecule reactions of pyridine and fluorine-containing compounds have been studied by the electron impact/Fourier transfer ion cyclotron resonance mass spectrometry (EI/FTICRMS). Comparing the reaction of the standard sample perfluorotributylamine (PFTBA), in the case of 3-oxa-5-iodo-octafluoropentylsulfonyl azide (ICF₂CF₂OCF₂CF₂SO₂N₃), a series of addition-elimination products and loss 28 from the expected adducts were obtained. A possible reaction mechanism was discussed, which was consistent with the results obtained in the condensed phase. These results demonstrated that EI/FTICRMS is a complementary technique for study of the organic reactions.     

Gas phase SN2 reactions of halide ions with trifluoromethyl halides: front- and back-side attack vs. complex formation

Density functional theory computations and pulsed-ionization high-pressure mass spectrometry experiments have been used to explore the potential energy surfaces for gas-phase S(N)2 reactions between halide ions and trifluoromethyl halides, X(-) + CF(3)Y --> Y(-) + CF(3)X. Structures of neutrals, ion-molecule complexes, and transition states show the possibility of two mechanisms: back- and front-side attack. From pulsed-ionization high-pressure mass spectrometry, enthalpy and entropy changes for the equilibrium clustering reactions for the formation of Cl(-)(BrCF(3)) (-16.5 +/- 0.2 kcal mol(-1) and -24.5 +/- 1 cal mol(-1) K(-1)), Cl(-)(ICF(3)) (-23.6 +/- 0.2 kcal mol(-1)), and Br(-)(BrCF(3)) (-13.9 +/- 0.2 kcal mol(-1) and -22.2 +/- 1 cal mol(-1) K(-1)) have been determined. These are in good to excellent agreement with computations at the B3LYP/6-311+G(3df)//B3LYP/6-311+G(d) level of theory. It is shown that complex formation takes place by a front-side attack complex, while the lowest energy S(N)2 reaction proceeds through a back-side attack transition state. This latter mechanism involves a potential energy profile which closely resembles a condensed phase S(N)2 reaction energy profile. It is also shown that the Cl(-) + CF(3)Br --> Br(-) + CF(3)Cl S(N)2 reaction can be interpreted using Marcus theory, in which case the reaction is described as being initiated by electron transfer. A potential energy surface at the B3LYP/6-311+G(d) level of theory confirms that the F(-) + CF(3)Br --> Br(-) + CF(4) S(N)2 reaction proceeds through a Walden inversion transition state.     

Using tandem mass spectrometry to predict chemical transformations of 2-pyrimidinyloxy-N-arylbenzyl amine derivatives in solution

Tandem mass spectrometry is used to predict the chemical transformations of 2-pyrimidinyloxy-N-arylbenzyl amine derivatives. Compound 1, N-2-2-4,6- dimethoxypyrimidin-2-yloxy benzylamino phenyl benzamide was selected as a model to present our idea. The CID reactions of protonated 1 include an intramolecular S(N)2 reaction and a cyclodehydration reaction. Under in-source CID conditions, deprotonated 1 undergoes a Smiles rearrangement reaction and then dissociates to the ion at m/z 349. Theoretical computations were invoked to shed light on the reaction mechanisms of 1 by the semiempirical PM3 method. These studies of gas-phase reactions show the reactivity of some potential reaction centers in this molecule, which inspired us to explore the solution phase analogous reactions of 1. Further experiments show that 1 has two analogous reactions in acidic solution: the acid-catalyzed cyclodehydration reaction and the acid-catalyzed Smiles rearrangement reaction. Moreover, 1 undergoes the base-catalyzed Smiles rearrangement under basic conditions. The present study demonstrates that mass spectrometry can play an important role in predicting the chemical solution phase transformations of 2-pyrimidinyloxy-N-arylbenzyl amine derivatives.     

Studies of rearrangement reactions of protonated and lithium cationized 2-pyrimidinyloxy-N-arylbenzylamine derivatives by MALDI-FT-ICR mass spectrometry

The rearrangement reactions of protonated and lithium-cationized 2-pyrimidinyloxy-N-arylbenzylamine derivatives were studied by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and infrared multiphoton dissociation mass spectrometry (IRMPD). Our results show that three kinds of rearrangement reactions occur in IRMPD processes. First, nearly all protonated 2-pyrimidinyloxy-N-arylbenzylamine derivatives undergo Pathway A to form the K ion series. It is proposed that this rearrangement (migration of a substituted benzyl group) proceeds by way of a gas-phase intramolecular S(N)2 reaction. Second, a gas phase intramolecular S(N)Ar type rearrangement mechanism is proposed to explain the formation of the F ion series from protonated and lithium-cationized 5 (or 6). This skeletal rearrangement reaction competes with the S(N)2 reaction of the Pathway A, which produces the K ion series, in IRMPD of protonated 5 and 6. Third, the formation pathway of the W ion series is explained by a gas phase Cope type rearrangement mechanism.     

Clustering of pentacene and functionalized pentacene ions in a matrix-assisted laser desorption/ionization orthogonal TOF mass spectrometer

A high-performance orthogonal time-of flight (TOF) mass spectrometer, in combination with the matrix assisted laser desorption/ionization (MALDI) source operating at elevated pressure (∼1 torr in N₂), was used to perform MALDI-TOF analyses of pentacene and some of its derivatives with and without an added matrix. These molecules are among the most interesting semiconductor materials for organic thin film transistor applications (OTFT). The observation of ion-molecule reactions between “cold” analyte ions and neutral analyte molecules in the gas phase has provided some insight into the mechanism of pentacene cluster formation and its functionalized derivatives. Furthermore, some of the matrices employed to assist the desorption/ionization process of these compounds were observed to influence the outcome via ion-molecule reactions of analyte ions and matrix molecules in the gas phase. The stability and reactivity of the compounds and their clusters in the MALDI plume during gas-phase expansion were evaluated; possible structures of the resulting clusters are discussed. The MALDI-TOF technique was also helpful in distinguishing between two isomeric forms of bis-[(triisopropylsilyl)-ethynyl]-pentacene.     

Troposelective substitutions in microsolvated systems.

The mechanism and the stereochemistry of the intracomplex "solvolysis" of the proton-bound complexes I(X)() between CH(3)(18)OH and (R)-(+)-1-aryl-ethanol (1(R)()(X)(); aryl = phenyl (X = H); pentafluorophenyl (X = F)) have been investigated in the gas phase in the 25-100 degrees C temperature range. The results point to intracomplex "solvolysis" as proceeding through the intermediacy of the relevant benzyl cation III(X)() (a pure S(N)1 mechanism). "Solvolysis" of I(H)() leads to complete racemization at T > 50 degrees C, whereas at T < 50 degrees C the reaction displays a preferential retention of configuration. Predominant retention of configuration is also observed in the intracomplex "solvolysis" of I(F)(). This picture is rationalized in terms of different intracomplex interactions between the benzylic ion III(X)() and the nucleophile/leaving group pair, which govern the timing of their reorientation within the electrostatic complex. The obtained gas-phase picture is discussed in the light of related gas-phase and solution data. It is concluded that the solvolytic reactions are mostly governed by the lifetime and the dynamics of the species involved and, if occurring in solution, by the nature of the solvent cage. Their rigid subdivision into the S(N)1 and S(N)2 mechanistic categories appears inadequate, and the use of their stereochemistry as a mechanistic probe can be highly misleading.     

Ion-molecule reaction mechanism of SiCN+/SiNC+ + HX (X = H, CH3, F, OH, NH2)

In contrast to the abundant data on the neutral-neutral reactions, little is known about the ion-molecule reactions involving silicon ions. A detailed mechanistic study at the B3LYP/6-311G(d,p) and CCSD(T)/6-311+G(2df,p) (single-point) computational levels was reported for the reactions of SiCN+/SiNC+ with a series of -bonded molecules HX (X = H, CH3, F, NH2). Together with the recently studied SiCN+/SiNC+ + H2O reactions, all of these reactions have nucleophilic substitution as their major pathway. Insertion is a much slower reaction. By contrast, the known atomic Si+ and C2N+ ion-molecule reactions go by insertion. Generally, the initial gas-phase condensation between SiCN+/SiNC+ and HX (except the nonionic H2) effectively forms the adduct HX...SiCN+/HX...SiNC+. The stability of the adduct increases with the electron-donating ability of X. Even at low temperatures, reactions with the electron donors NH3, H2O, and HF proceed rapidly to generate the fragments SiX+ + HCN (dominant) and SiX+ + HNC (minor). This suggests that such reactions may be useful in the synthesis of novel Si-X bonded species. However, the reactions of SiCN+ with completely saturated CH4 and H2 produce fragments only at high temperatures, and SiNC+ may even be unreactive. The calculated results may be helpful for understanding the chemistry of SiCN-based microelectric and photoelectric processes in addition to astrophysical processes in which the [Si,C,N]+ ion is involved. The results can also provide useful mechanistic information for the analogous ion-molecule reactions of the monovalent silicon-bearing ions.     

Gas-phase bimolecular reactions between (.)CH(2)-(CH(2))(n)-C(+)=O distonic ions and pyridine: a combined experimental and theoretical study

The gas-phase reactivities of the well-known (.)CH(2)CH(2)C(+)=O and (.)CH(2)CH(2)CH(2)C(+)=O distonic ions towards neutral pyridine were studied both experimentally (six sector hybrid mass spectrometer) and theoretically (density functional theory and M?ller-Plesset ab initio calculations). Competitively to the charge exchange and protonation processes, both radical cations react with pyridine by an initial bonding between the positive charge site of the ion and the lone electron pair of the neutral molecule. At variance with previously reported studies in which such a nucleophilic interaction was proposed to play only a transient catalytic role, the initial C-N bond is likely to remain in the observed ion-molecule reaction products. The structures of the ion-molecule reactions products were probed by collisional activation at high kinetic energy and the reaction pathways were tentatively proposed on the basis of labeling experiments and ab initio molecular orbital calculations.     

Investigation of the Gas-Phase Structure of Electrosprayed Proteins Using Ion-Molecule Reactions

Proton transfer reactions of ammonia, dimemylamine, diethylamine, and trimethylarnine with multiply protonated proteins generated by electrospray ionization (ESI) were examined to probe the relationship between solution and gas-phase protein structure and the relationship with ion-molecule reactivity. The ion-molecule reactions were carried out in an atmospheric pressure capillary inlet/reactor based upon an ESI interface to a quadrupole mass spectrometer. Two types of systems were explored: (1) proteins possessing cysteine-cysteine disulfide bonds and the analogous disulfide-reduced proteins, and (2) proteins sprayed from solution compositions where the protein has different conformations. While the cysteine-cysteine disulfide-bound proteins were more reactive than equally charged disulfide-reduced proteins under these conditions, no significant reactivity differences were noted for ions arising from different solution conformations. The effect of inlet/reactor temperature on charge distributions with and without amine reagent was also explored, demonstrating that thermal denaturation of proteins can occur in heated capillary inlets. The results are discussed in the context of recent results indicating the persistence of at least some higher order protein structure in the gas phase.