苯甲醛肟与炔丙醇偶极环加成反应的理论研究

用密度泛函理论(DFT)方法在B3LYP/6-31G*水平上研究了苯甲醛肟与炔丙醇加成反应的微观机制和热力学、动力学行为. 结果表明, 在苯甲醛肟与炔丙醇加成反应过程中, 8个可能反应通道的过渡态中均形成非平面五元环结构, 其中苯甲醛肟的Z、E构型特征得到了部分保留, 但主要部分的键长、键角均发生了变化, 电荷也进行了重新分布. 苯甲醛肟以羟基型参与反应的4个反应通道均为吸热反应和热力学非自发过程, 它们均具有较高的反应势垒、较慢的反应速率和较小的平衡常数; 而以离子型参与反应的四个反应通道均为放热反应和热力学自发过程, 它们的反应势垒较低, 反应速度较快, 平衡常数也较大, 故苯甲醛肟应主要以离子型参与反应. 炔丙醇的两种取向对应着加成反应的两种产物, 反应达到平衡后, 3-羟甲基二氢异噁唑为主要产物.     

取代苯甲醛肟和取代苯乙酮肟电化学氧化机理的研究

研究了１０种取代苯甲醛肟和５种取代苯乙酮肟的电化学氧化机理。这二类肟的氧化电位随取代基吸电子能力的增大而增高，并与它们相应的Ｈａｍｍｅｔｔ常数有线性关系。它们在电化学氧化过程中均有ｉｍｉｎｏｘｙ自由基生成，但最后产物各不相同。用控制电位电解和紫外吸收光谱检法验证了部分电化学氧化产物。因此，电化学氧化法可作为由肟类产生ｉｍｉｎｏｘｙ自由基的一种方法。     

水溶液中亚硝基甲烷与甲醛肟之间互变异构反应的理论研究

采用超分子-连续介质(PCM)模型,在密度泛函B3LYP/6-311++G^**水平上对水溶液中亚硝基甲烷异构化反应的机理进行了理论研究.结果表明,在水溶液中亚硝基甲烷可以通过两条反应途径(Ⅰ和Ⅱ)经质子迁移得到更稳定的重排产物--反式甲醛肟,但优势反应途径与在气相反应不同.在水溶液中亚硝基甲烷异构化反应最有可能的途径Ⅰ是通过氢迁移先生成顺式甲醛肟,然后绕N-O键旋转生成更稳定的反式甲醛肟.并且由于水分子的催化作用使得反应活化能从气相中240.6和196.2 kJ/mol分别降低至水溶液中的61.7和92.1 kJ/mol.     

在微流控芯片上合成对甲氧基苯甲醛肟

本文用负压进样的方法, 在自制的玻璃微流控芯片中进行了对甲氧基苯甲醛和盐酸羟胺合成对甲氧基苯甲醛肟的相转移反应. 测定了不同反应时间的产率, 并与常规方法进行了比较. 讨论了相接触面积和塞流对产率的影响.     

取代苯甲醛肟羧酸酯的合成及生物活性研究Ⅵ.4-二甲氨基苯甲醛肟酯的合成及生物活性

苯甲醛肟酯;取代苯甲醛肟羧酸酯的合成及生物活性研究Ⅵ.4-二甲氨基苯甲醛肟酯的合成及生物活性     

偶极-偶极相互作用的探讨(Ⅱ)

增强拉曼光谱和红外光谱是研究金属电极上吸附分子间振动相互作用的有力工具．分子间的振动相互作用主要通过它们的偶极场，吸附分子吸附峰强度的转移与它们的电子极化率的屏蔽作用密切相关·相关势近似（CoherentPotentialApprokimation，CPA）已广泛用于讨论分子间的振动相互     

偶极-偶极相互作用的探讨(I)

用增强拉曼光谱和电势调节红外光谱探讨偶极－偶极相互作用时，吸附带强度变化比频率位移更为重要．因为其它因素，如吸附物位置不均匀，通过金属表面的诱导作用等也能引起频率的稍微位移，但这些因素均不能解释强度转移效应．分子间的振动相互作用主要通过它们的偶极场，吸附分子吸收峰强度的转移与它们的电子极化率的屏蔽作用密切相关，相关势近似（CPA，CoherentPotentialApproximation）已广泛用于讨论分子间的振动相互作用［1］．本文用CPA方法计算了C（ZXZP’CN一、“CN丫All（100）体系的吸收光谱，并与吸附在粗化金电极上的…     

偶极-偶极相互作用的探讨(II)

The coherent potential approximation (CPA) was used in the calculation of the vibrational spectra for absorbed 12CO/13CO mixtures on platinum. The theoretical results were compared with the surface IR-spectra of 12CO/13CO mixture absorbed on Pt-electrode. The results show that in the systems consisting of isotopic mixtures of CO on Pt(001), molecules interact mainly through their dipole fields.     

取代苯甲醛肟羧酸酯的合成及生物活性研究：I.取代苯甲醛肟二氯菊酸酯 …

探讨了α－取代苯甲醛肟合成的新方法，合成了２０种新型菊酸肟酯类化合物，并对其进行了初步生物活性测试，化合物５ａ，５ｆ具有很好的抗病毒活性。     

取代苯甲醛肟羧酸酯的合成及生物活性研究──Ⅰ.取代苯甲醛肟二氯菊酸酯的合成及生物活性

探讨了α-取代苯甲醛肟合成的新方法,合成了20种新型菊酸肟酯类化合物,并对其进行了初步生物活性测试,化合物5a,5f具有很好的抗病毒活性.     

顺铂化合物与鸟嘌呤异构体相互作用的理论研究

The influence of binding of cisplatin adducts on tautomeric equilibrium of guanine was investigated using quantum chemical method. The monoaqua adduct [Pt（NH3）2Cl（H2O）]^＋ and the diaqua adduct [Pt（NHa）2（H2O）2]^2＋ were chosen for coordination to the N（7） site of guanine tautomers. The results demonstrate that the platinum adducts influence moderately on tautomeric equilibrium, but do not change the relative stability of tautomers whether in gas phase or in aqueous solution. The keto form having H atom at N（1） and N（9） was always the predominant structure when cisplatin adducts were bound to guanine. However, other forms could coexist in water. Meanwhile, our calculations suggest that the tautomeric equilibrium should be via the same intermediate.     

Theoretical Study on the Tautomerization Reaction of Formamide to Formamidic Acid Encapsulated in a Nano-sized Molecular Container

The hybrid calculations with ONIOM(B3LYP/6-31G*:AM1) method were carried out on the tautomerization reaction of formamide to formamidic acid in the microcontainer-encapsulated state. The free-state tautomerization process was also investigated with B3LYP/6-31G**//B3LYP/6-31G* method for the purpose of comparison. Bare tautomerization, H2O-assisted(single-H2O or multiple-H2O) and self-assisted mechanisms were all taken into consideration for the encapsulated state. The results show that only bare tautomerization and single-H2O catalysis mechanisms are possible to the encapsulated for-mamide tautomerization owing to the container's size confinement effect. Geometrical changes in the complexed container and guest molecules are discussed to deeply understand the complex's structural properties. The bare tautomerization barrier in the encapsulated state increases by 23.826 kJ/mol, ac-counting for 12% of the corresponding total energy barrier in the free state, and the increased values for the single-H2O catalysis process are 12.958 kJ/mol, accounting for 16% of the corresponding total energy barrier, respectively. This finding suggests that the encapsulation can make the tautomerization process slightly difficult.     

2-羟基吡啶与水氢键作用的理论研究

本文采用量子化学的Hatree-Fock方法和密度泛函理论(DFT)的B3LYP方法,在6-31G(d)水平上,研究了2-羟基吡啶分子(Hy)及其酮式互变异构体2(1H)-吡啶酮(Py)与水的相互作用。考察它们之间在形成Hy…H2O,Py…H2O,Hy…Hy,Py…Py和Hy…Py等复合物前后的能量变化和分子结构参数变化特点。计算结果表明,在这些复合物中都形成了较强的氢键作用,在水合物中,Py与水形成复合物时能量降低较多,与实验结果一致。经过零点振动能(ZPVE)和基组叠加误差(BSSE)校正后的复合物离解能分别为38.3,40.8,73.0,82.7和71.1 kJ/mol(B3LYP/6-31G(d)),水合物的离解能远小于二聚体复合物,而酮式结构的二聚体的离解能最大。     

Theoretical Study of the Intramolecular Proton Transfer in the Tautomers of Cytosine Assisted by Water

Ab initio MP2 and DFT studies on the tautomers of cytosine and the related hydrated tautomers have been carried out. The ground‐state structures of four tautomers of cytosine and related transition states were fully optimized. The vibrational frequency analysis was performed on all the optimized structures. Detailed intrinsic reaction coordinate (IRC) calculations were carried out to guarantee the optimized transition‐state structures being connected to the related tautomers. We obtained the relative stability order for the tautomers of cytosine and the related hydrated tautomers. In the isolated and hydrated condition, the bond types of C(2) O(7) and C(4) N(8) greatly affect the stability of the cytosine tautomers. Moreover, we have explored the influence of the water molecules on the intramolecular proton transfer between the keto and enol forms of the cytosine tautomers. The first water molecule obviously decreases the isomerization activation energy for the monohydrated cytosine tautomers. It is shown that the isomerization energy barrier changes only a little when the second and third water molecules are added in the reaction loop. The solvent effects have an obvious influence on the proton‐transfer barrier of the isolated cytosine. However, the solvent effects seem to be insignificant for the isomerization energy barriers of the monohydrated, dihydrated and trihydrated cytosine. The water molecule in these complexes can be looked on as the explicit water. Therefore, the explicit water model may be more credible to explore the intramolecular proton transfer, in comparison with the PCM which is the implicit water model.     

Experimental and Computational Studies of the Isomerization between Z and E Isomers of Benzaldoximes

The isomerization between Z and E isomers of benzaldoximes in different solvents were measured by TLC method. The experimental results show that acid solvents catalyze this inter‐conversion process dramatically. Solution state NMR measurements also show very different spectra for Z and E isomers of benzaldoximes in different solvents. All this suggests that the acidity of solvent is a very important factor to affect the inter‐conversion process. Theoretical investigations of Z to E inter‐conversion of benzaldoximes in different solvents were carried out by DFT calculations at B3LYP/6–3 11+G** level. The calculations show that the barrier from Z to E in the presence of acid is much lower than that without acid. This agrees with the experimental data very well. The calculated structure in the transition state is helpful for the understanding of the inter‐conversion mechanism.     

5-氟尿嘧啶和5-氯尿嘧啶及其互变异构体的理论计算研究

采用HF/3-21G方法, 对6种气相和水相中可能存在的5-氟尿嘧啶(和5-氯尿嘧啶)互变异构体进行了构象分析.采用B3LYP/6-311＋G**方法对处于优势构象时的各互变异构体进行了几何全优化, 并计算出它们的总能量、焓、熵、吉布斯自由能. Onsager反应场溶剂模型用于水相的计算. 计算结果表明, 5-氟尿嘧啶和5-氯尿嘧啶在气相中和水相中主要以双酮形式存在. 5-氟尿嘧啶和5-氯尿嘧啶的熵效应小, 对互变异构平衡没有显著的影响, 而焓变对互变异构产生了主要的影响. 讨论了水溶剂化作用对异构体的能量、电荷分布和偶极矩的影响. 溶剂化自由能与异构体的气相偶极矩存在相关性. 另外, 详细地将5-氟尿嘧啶和5-氯尿嘧啶与尿嘧啶进行了对比, 获得三者最稳定异构体间电子结构异同的有用信息.     

Theoretical Study on the Addition Reactions of Benzaldoximes with Propene

Nitrones are useful in the preparation of many interesting compounds such as amino aldehydes, aminosugars, aza sugars, amino acids, aminoalcohols, peptide isosteres and nucleoside analogs. Nitrones are generally prepared by the condensation reactions of c…     

四唑衍生物异构化反应的理论研究

运用ＭＮＤＯＭＯ法对五种四唑衍生物的互变异构反应进行了理论计算,结果表明,过渡态的几何构型主要由迁移基团所决定,迁移基团的电性对反应速度影响很大,反应活化能与反应物中断裂键的键级和迁移基轩处净民荷之间均存在良好的线性关系,二取代基的性质均对反应平衡常数产生影响。     

Reactions of 1-Hydro-5-carbaphosphatrane: Tautomerization between Five-Coordinate and Three-Coordinate Species

Oxidation, sulfurization, and selenation of a 1-hydro-5-carbaphosphatrane afforded the corresponding cyclic phosphonate, cyclic phosphonothioate, and cyclic phosphonoselenoate, respectively. These results indicate the existence of the tautomerization between the five-coordinate 5-carbaphosphatrane and the three-coordinate cyclic phosphonite.     

杀螟丹中间体与异构体互变[JZ]异构理论研究

研究了合成杀虫剂杀螟丹的关键中间体2-N,N-二甲胺基-1,3-二硫氰基丙烷(有效体)及其异构体1-N,N-二甲胺基-2,3-二硫氰基丙烷(无效体)互变异构反应中溶剂和温度的影响. 采用密度泛函理论B3LYP/6-31G(d)方法研究了其在气相中的反应机理, 确定了相应的过渡态和反应活化能. 量子化学计算结果表明, 反应首先通过分子内亲核取代环化生成吖丙啶鎓盐活性中间体, 硫氰基进攻N-三元环中间体过程中发生了分子内重排转位, 转化为异构体. 采用极化连续(Polarizable continuum model, PCM)模型研究了反应体系在甲苯、氯仿、丙酮、乙醇、甲醇、乙腈和DMSO溶液中的溶剂效应. 结果表明, 该重排反应溶剂化效应非常明显, 极性溶剂有利于过渡态的稳定, 降低反应活化能, 提高反应速率. 理论研究结果与实验观察结果相符, 很好地解释了有关实验现象.