THEORETICAL STUDIES ON THE REACTION MECHANISM OF AMMONIA WITH FORMALDEHY DE

The reaction mechanism of ammonia with formaldehyde was investigated by usingthe intrinsic reaction coordinate(IRC)method on the ab initio RHF/STO-3G basis set.our results indicate that the reaction proceeds in two stages:the first step yieldsthe molecular complex and the second one is the rearrangement from molecular complex tothe reaction proauct.     

AB INITIO STUDIES ON THE REACTION MECHANISH OF CYCLOADDITION OF KETENE AND FORMALDEHYDE

The cycloaddition reaction of ketene and formaldehyde,lesding to 2-oxetanone,has been studied theoretically by means of RHF/3-21G.This reactionis believed to be nonsynchronous but concerted,taking place through a twistedfour membered ring transition state.Two types of frontier orbitalinteractions are involved in this reaction.The activation barrier iscalculated to be 123.1KJ/mol (MP2/3-21G result).     

STUDIES ON THE REACTION OF ORGANOTELLURONIUM SALTS

The structural studies of the telluronium saltrformation betweendibutyl telluride and secondary (?)-bromo compounds and the use of the obtai-ned salts for the olefination of carbonyl compounds were reported.     

STUDIES ON THE REACTION OF d-ACETAMIDCCINNAMAMIDE WITH TRIS(DIETHYLAMINO)PHOSPHINE

d-Acetamidocinnamamide do not react with P(OMe)_3, with P(NEt_2)_3 they give rise to 2-methyl-4-hydroxy-5-d-[bis(diethylamino)phosphoryl] benzyl imidazole.The pathway is studied for the formation of Ⅰ. The two intermediates(Ⅱ) are isolated.The structures of Ⅰ and Ⅱ are confirmed by IR, ~1H NMR, ~(31)P NMR, Ms.     

THEORETICAL STUDIES ON THE SUBSTITUTION EFFECT OF FLUORINE ON ETHANE

<正> The substitution effect of fluorine on ethane has been investigated by means of studying the properties of the charge distribution at the bond critical points with the theory of atoms in molecule.It is found that the major substitution effects of fluorine atom are positive a inductive and polarity effect.At the same time,fluorine atom partially provides π electrons to other chemical bonds by means of hy-perconjugation in molecules with two fluorine atoms and one or two carbon atoms in the same plane,and these effects are reflected in the quantity of bond ellipticity,Laplacian and the charge density of charge distribution at the bond critical points.The substitution of hydrogen by fluorine in ethane strengthens all the bonds in substituted ethanes.Other effects originating from the substitution of hydrogen by fluorine have also been discussed.     

THEORETICAL STUDIES ON THE INTRINSIC REACTION COORDINATE OF THE REACTION HCO＋HNO_2→HCHO＋NO_2

ＴＨＥＯＲＥＴＩＣＡＬＳＴＵＤＩＥＳＯＮＴＨＥＩＮＴＲＩＮＳＩＣＲＥＡＣＴＩＯＮＣＯＯＲＤＩＮＡＴＥＯＦＴＨＥＲＥＡＣＴＩＯＮＨＣＯ＋ＨＮＯ_２→ＨＣＨＯ＋ＮＯ_２￥ＸｉａｎＹｏｎｇＰＡＮＧ；ＹａｎＷＡＮＧ；ＹｏｎｇＰｉｎｇＹＡＮＧ；ＷｅｎＬｉｎＦＥＮ...     

THEORETICAL STUDIES ON THE UNIMOLECULAR DISSOCIATION OF METHYLFORMATE CATION

The unimolecular dissociation of methylformate free radical cation(CH_3OCHO~+) was studied by ab initio theoretical calculations, Molecular orbital and state correlation diagrams have been examined in the ground and lower excited states. The dissociation mechanism has been explained along the reaction paths. For two possible dissociation pathways in the ground and lower excited states, the activation barriers and reaction heats have been calculated by MCSCF method respectively.     

MHEORETICAL STUDIES ON THE REACTION MECHANISMS OF CYCLOADDITION REACTIONS BETWEEN KETENE OR SUBSTITUTED KETENES AND CYCLOPENTADIENE

The cycloaddition reactions between ketene or substituted ketenes andcyelopentadiene have been studied theoretically by means of the semiempirical AMImethod.Three different substituted ketenes have been selected and tentransition states,corresponding to different approach geometries have beenlocated and characterized,The regioselectivity and stereoselectivity of thereactions are correctly predicted by the calculations and the reaction mechanismsare analyzed in terms of electronic and steric effects of the substitutents onthe reacting ketene and cyc-lopentadiene.     

STUDIES ON THE INTERACTION OF EPOXY POLYMERS WITH HOMOPOLYUREAS

INTRODUCTION Epoxy resins are reactive polymers which when cured with a variety of chemicals lead to a host of useful thermosets. Since the epoxide is a strained ring, it readily undergoes addition and homopolymerization. The homopolymerization is a process catalysed by acids, bases, Lewis acids, t-amines as well as by inorganic salts.     

THEORETICAL STUDY ON PHOTODECARBONYLATION REACTION OF ACROLEIN

Photodecarbonylation reaction of acrolein at 193nm was investigated by abinitio molecular orbital method.Our result supports photodecarbonylation mechanismsproposed by Fujimoto,and predicts that the reaction should occur in ~3ππ potentialenergy surface prior to the ~1ππ potential energy surface.     

STUDIES ON CYCLOADDITION REACTIONS OF VINYLPHOSPHONATES WITH NITRONES

Cycloaddition reactions of vinylphosphonates with nitrones were studied. A series of 4-phosphonyl-3-aryl-N-arylisoxazolidines were synthesized by the reaction of vinylphosphonates with nitrones. The structure of 3a was confirmed by X-ray single-crystal diffraction.     

STUDIES ON THE STEREOMECHANISM OF THE REACTION OF SULPHIDES WITH CHLORAMINE-T

Abstract

In the reactions of sulphides (RQS) with chlaramine-T (TsNClNa) sulphilimines (RQSNTs) and sulphoxides (RQSO) are known to be produced from a chlorosulphonium-sulphon-amidate ion-pair intermediate (RQSC1⁺, TsNH^?) in fast competitive S_N reactions of different steric controll. The stereomechanism was investigated in reactions of sulphides (RQ?S) with asymmetric carbon atom adjacent to sulphur, leading to diastereomeric sulphilimines (RQ?S?NTs) and sulphoxides (RQ?S?O). The proportions and the configurations of the diastereomers of both products were determined. The efficiency of the asymmetric induction was found to depend on the bulkiness of the substituents of sulphides. The major diastereomeric components of the produced sulphilimines and sulphoxides proved to have opposite configurations about sulphur. On this basis, the hydrolysis of chlorosulphonium ion yielding sulphoxide is assumed to proceed through a sulphurane intermediate via an a-a type ligand exchange, while the formation of sulphilimine from chlorosulphonium -sulphonamidate ion-pair may involve an a-e type displacement.     

咪唑与单线态氧(~1O_2)1,2-环加成反应的理论研究

采用较新的半经验分子轨道方法Austin Model 1(简称AM1方法),辅以Berny梯度优化方法,对单线态氧(~1O_2)与咪唑的1,2-环加成反应,进行了理论研究。计算获得实验尚未检测到的4,5-二氧环丁烷(4,5-dioxetane)的结构,并在反应势能面上找到单重态双自由基中间体及通过该中间体的两步反应的过渡态。通过对过渡态的结构特征、虚振动方向以及对反应过程的电荷分布情况、轨道相互作用等的分析,说明该反应是经由单重态双自由基中间体的分步反应。两步反应的活化势垒分别为39.2kJ·mol~(-1)和150.5kJ·mol~(-1)。     

5—（L—盖氧基）—2（5—H）—呋喃酮与硝酮体系环加成反应的理论研究

选取模型化合物,用AMl MO方法从理论上研究了手性的5-(L-盖氧基)-2(5—H)-呋喃酮与偶极硝酮体系环加成反应的机理。优化了反应过程各驻点的几何构型,计算了反应的活化焓、活化熵和反应速率常数,结果表明,该反应为同面的协同过程,非对映专一性产物的形成估计是由于盖氧基及硝酮分子上苯取代基的空间效应所致。     

灿烂绿新体系催化动力学分光光度法测定痕量铜

铜是人体必需的微量元素之一。缺铜将引发各种疾病 ,因而对水中痕量铜的检测是十分必要的。催化动力学分析法是一种高灵敏度的分析方法 [1-6] ,用于铁的测量已有不少报道 [1-4 ] ,但用灿烂绿作指示剂催化动力学光度法测定铜还未见报道。本文发现在 p H=4 .5的 HAc- Na Ac缓冲介质中 ,Cu2 对过氧化氢氧化灿烂绿有明显的催化作用。据此研究了适宜的催化条件 ,建立了催化动力学光度法测定痕量铜的新方法。该反应可表示为灿烂绿 H2 O2Cu2 ,H 氧化产物反应速率方程为 :- dc灿烂绿 /dt=kca灿烂绿 cb Cu2 cm H2 O2 cn H 但由于缓冲溶…     

对硝基苯基荧光酮与铁显色反应的研究及应用

研究了在表面活性剂CPB及Triton X-100存在下,对硝基苯基荧光酮与铁显色反应的条件.结果表明,在pH6.5缓冲介质中,铁与对硝基苯基荧光酮、CPB及Triton X-100生成多元络合物的最大吸收波长在582nm,表观摩尔吸光系数为1.65×10~5,铁量在0～10μg/25ml范围内遵循比耳定律,方法经实际试样验证,结果令人满意,并对反应机理进行了探索.     

氟化氢与涂有聚合物膜下二氧化硅的反应研究

ＨＦ与ＳｉＯ２的反应是一种亲核取代反应，但高温下此反应不能发生．当涂覆在ＳｉＯ２表面的聚合物膜中含有某些特殊的有机化合物或超强酸时，可以促进该反应的发生，这些化合物被称为诱蚀剂．诱蚀剂分三类：（１）三级胺与ＨＦ形成季铵盐得到浓度很高的氟阴离子使该反应很容易发生；（２）强的偶极非质子官能团化合物与ＨＦ中的氢形成氢键使氟的亲核活性增加，有助于该反应发生；（３）超强酸因其质子对ＳｉＯ２骨架中氧的牢固结合能力活化了反应的离去基团，对ＨＦ与ＳｉＯ２的亲核反应起到催化作用．聚合物膜对添加在其中的小分子诱蚀剂起到阻止逃逸的栅栏作用，而本身带有诱蚀官能团的聚合物可以同时充当成膜物及诱蚀剂的作用．通过光化学反应可以选择性地实现聚合物膜下ＨＦ与ＳｉＯ２的刻蚀反应．