三重态类硅烯HB＝SiLiF的结构及其与R—H(R=F,OH,NH_2)的插入反应

用密度泛函理论(DFT)和二次组态相互作用(QCISD)方法研究了三重态类硅烯HB=SiLiF的结构及其与RH(R=F,OH,NH2)的插入反应.计算结果表明,类硅烯HB=SiLiF有三种平衡构型,其中四元环构型能量最低,是其存在的主要构型.HB=SiLiF与HF,H2O和NH3发生插入反应的机理相同.QCISD/6-311++G(d,p)//B3LYP/6-311+G(d,p)计算的三个反应的势垒分别为124.85,140.67和148.16kJ·mol-1,反应热分别为-2.22,20.08和23.22kJ·mol-1.相同条件下发生插入反应时,反应活性都是H—FH—OHH—NH2.     

类卡宾CH2ClLi和甲醛加成反应机理的从头算

以HF/6-31G*基组研究了类卡宾CH2ClLi和甲醛在四氢呋喃溶液中的加成反应机理.CH2ClLi和甲醛,首先生成一个初期络合物,并伴有明显放热.络合物经一个平面双环结构的过渡态到达产物,仅需要一个很小的活化能(14.6 kJ/mol).在这个羰基加成过程中,甲醛羰基碳的亲电进攻较类卡宾碳的亲核进攻表现得更加活跃.整个反应放热效应达216.5 kJ/mol.     

二氯硅烯与乙烯和甲醛环加成反应机理的理论研究

用RHF/6-31G^*解析梯度方法研究了单重态二氯硅烯与乙烯和甲醛环加成反应的机理,并用二级微扰方法对各构型能量进行了相关能校正.结果表明,两反应历程均由两步组成:(1)二氯硅烯与乙烯和甲醛分别生成了中间配合物,是无势垒的放热反应;(2)中间配合物异构化成产物二氯硅杂环丙烷和二氯硅杂环氧甲烷,其势垒经零点能校正分别为97.43和103.29kJ/mol(MP₂/6-31G^*//6-31G^*).     

杂环型稳定硅烯插入HF、H_2O和NH_3反应

硅烯为卡宾的硅类似物,在有机光和热化学中作为一类重要的反应活性中间体引起了化学界的广泛兴趣.杂环型硅烯是实验合成的稳定硅烯,因其在有机硅化学中的重要作用,十几年来在实验和理论上均有研究报道.本文基于单重态杂环型硅烯的特殊电子性质和丰富的化学反应性,系统探讨了几种杂环型硅烯的插入反应.使用密度泛函理论(DFT),在B3LYP/6-311++G(d,p)水平上研究了三种氮杂环型不饱和硅烯(1,3,4)和两种氮杂环型饱和硅烯(2,5)分别与H—X(X=F,OH,NH2)键的插入反应,阐明了插入反应的机理并对各反应的结果进行了比较.杂环型硅烯与H—X的插入反应机理类似于简单硅烯,体现了硅烯的亲电亲核的双重反应性.由反应势垒和反应热看,五种硅烯与H—X键的插入反应均为HF最容易,H2O次之,NH3最难.饱和硅烯的反应性比不饱和硅烯的反应活性高,这也间接验证了杂环型饱和硅烯在实验中较难合成.     

类硅烯H2C＝SiLiBr与RH (R＝F, OH, NH2)的插入反应

采用DFT B3LYP和QCISD方法研究了类硅烯H2C＝SiLiBr与RH (R＝F, OH, NH2)的插入反应. 在B3LYP/6- 311＋G(d,p)水平上优化了反应势能面上的驻点构型. 结果表明, H2C＝SiLiBr与HF, H2O或NH3发生插入反应的机理相同. QCISD/6-311＋＋G(d,p)//B3LYP/6-311＋G(d,p)计算的三个反应的势垒分别为148.62, 164.42和165.07 kJ•mol－1, 反应热分别为－69.63, －43.02和－28.27 kJ•mol－1. 相同条件下发生插入反应时, 反应活性都是H—F＞H—OH＞H—NH2.     

CH3F与C2H3反应机理的理论研究

采用密度泛函B3LYP/6-311G(d,p)方法对CH3F与C2H3的反应体系进行了理论研究,获得了反应的势能面信息及可能的微观机理.在QCISD(T)/6-311++G(d,p)水平上精确计算了各反应物种的单点能.结果表明,除抽提氢反应外,标题反应还存在抽提氟(R1)、消氟化氢(R2)、消氢(R3)和自由基形成(R4)四类反应.在QCISD(T)/6-311++G(d,p)//B3LYP/6-311G(d,p)水平上,R1,R2,R3和R4反应的能垒分别是163.9,152.2,209.8和224.2kJ·mol-1,相应反应能为-56.6,-164.3,-2.7和-156.0kJ·mol-1,所有反应均放热,为热力学允许的反应.     

手性双噁唑啉金属络合物催化N-α,β-不饱和酰基化合物与C,N-二芳基硝酮的不对称1,3-偶极环加成反应

研究了Inda-BOX1金属络合物为催化剂的两种缺电子烯烃与C,N-二芳基硝酮的不对称环加成反应.研究结果表明,在催化剂存在的条件下,两反应均可得到4-位取代产物.其中N-丙烯酰基噁唑烷酮为亲偶极体时,反应的exo/endo选择性达到100/0,且exo产物的ee值高达97%; N-丙烯酰基-3,5-二甲基吡唑为亲偶极体时, exo/endo选择性为0/100,且endo产物的ee值高达98%.对亲偶极体及硝酮结构与反应选择性之间的关系进行了初步探讨.     

ZnCl2/粘土-SA01催化合成二苯甲烷反应动力学研究

在ZnCl2/粘土-SA01催化剂上合成了二苯甲烷,考察了负载量、苯/苄基氯摩尔比、催化剂用量、反应温度和时间对该反应的影响,研究了以ZnCl2/粘土-SA01为催化剂合成二苯甲烷的反应动力学,为探讨其反应机理和研究烷基化反应动力学提供了依据.结果表明,温度在303-318K时,本征动力学方程为r=k[ZnCl2/粘土-SA01]0.8[C6H6][C6H5CH2Cl],属二级反应,表观反应活化能为88.6kJ/mol;在328-353K时,其本征动力学方程为r=k[ZnCl2/粘土-SA01]0.1,反应属零级反应,表观活化能为52.8kJ/mol.     

3NaBH4/ErF3复合储氢材料的制备及吸放氢特性

采用高能球磨法制备了3NaBH4/ErF3复合储氢材料, 并研究了其相结构和储氢性能. X射线衍射(XRD)显示, NaBH4和ErF3在球磨过程中未发生反应; 同步热分析(TG-DSC)测试结果表明, 3NaBH4/ErF3体系在420℃开始放氢, 比相同测试条件下纯NaBH4的放氢温度降低了约100℃, 放氢量为3.06%(质量分数). 压力-成分-温度(Pressure-Composition-Temperature, PCT)性能测试结果显示, 3NaBH4/ErF3复合储氢材料在较低的温度(355~413℃)及平台氢压(<1 MPa)下即拥有良好的可逆吸放氢性能, 最高可逆吸氢量可达到2.78%(质量分数), 吸氢后体系重新生成了NaBH4相. 计算得吸氢焓变仅为-36.8 kJ/mol H2; 而放氢焓变为-180.8 kJ/mol H2. NaBH4在ErF3的作用下提高了热动力学性能, 并实现了可逆吸放氢.     

卡宾与醚C-H键插入反应的理论研究(Ⅲ)--CX2(X=H, F, Cl)与甲乙醚C-H键插入反应

用量子化学从头计算方法在MP2/6-31G(d)水平上研究了CX2(X=H, F, Cl)与甲乙醚的C-H键插入反应. 在甲乙醚的 3个不同的C-H键(即甲基中α-C-H键, 乙基中α-C-H键和β-C-H键)上, 反应势垒分别为123.8, 32.5, 157.3 kJ/mol(X=Cl)和254.3, 130.0, 304.2 kJ/mol(X=F). 亚甲基与毗邻氧原子的各C-H键插入反应没有势垒, 与乙基中β-C-H键插入势垒仅3.4 kJ/mol. 甲乙醚中乙基α-C上的C-H键最有利于CX2的插入, 甲基上的C-H键次之, 乙基β-C上的又次之.     

Theoretical studies of the geometries of H2GeNaF and its insertion reaction with R?H (RF,OH, NH2, CH3)

The geometries and insertion reactions of germylene H₂GeNaF with R? H (R?F, OH, NH₂, CH₃) have been investigated at the B3LYP/6‐311+G level of theory. The potential barriers of the four reactions are ～52, 120, 184, and 257 kJ/mol, including the ZPVE corrections, respectively. Here, all the mechanisms of the four reactions are identical to each other; i.e., an intermediate has been located during the insertion reaction. The intermediate could dissociate into substituted germylane and NaF with the barrier corresponding to the dissociation energy. Correspondingly, the reaction energies for the four reactions are ?43, ?4, 21, and 51 kJ/mol, respectively. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006     

Theoretical studies of the geometries of H2GeLiCl and its insertion reaction with R-H (R = F,OH, NH2)

The geometries and insertion reactions of germylene derivative H₂GeLiCl with R-H (R = F, OH, NH₂) have been investigated at the B3LYP/6-311+G^* level of theory. The potential barriers of the three reactions are 93.5, 151.3, and 194.1 kJ/mol, including the zero-point vibration energy corrections, respectively. The mechanisms of all the three reactions are identical, i.e., an intermediate has been located during the insertion reaction. The intermediate could dissociate to substituted germylene and LiCl as a barrier process. Correspondingly, the reaction free energies for the three reactions are −7.4, 49.9, and 64.4 kJ/mol, respectively.

     

Theoretical studies on the alkylidene germylenoid H<Subscript>2</Subscript>C=GeLiF and its insertion reaction with R-H (R = F,OH, NH<Subscript>2</Subscript>, CH<Subscript>3</Subscript>)

The geometries and isomerization of the alkylidene germylenoid H₂C=GeLiF as well as its insertion reactions with R-H (R = F, OH, NH₂, CH₃) have been systematically investigated at the B3LYP/6-311+ G* level of theory. The potential barriers of the four insertion reactions are 110.6, 145.0, 179.4, and 250.6 kJ/mol, respectively. Here, all the mechanisms of the four reactions are identical to each other, i.e., an intermediate has been formed first during the insertion reaction. Then, the intermediate could dissociate into the substituted germylene (H₂C=GeHR) and LiF with a barrier corresponding to their respective dissociation energies. Correspondingly, the reaction energies for the four reactions are 43.6, 78.8, 113.5, and 128.0 kJ/mol, respectively. Compared with the insertion reaction of H₂C= Ge∶ and R-H, the introduction of LiF makes the insertion reaction occur more difficultly. Furthermore, the effects of halogen (F, Cl, Br) substitution and inorganic salts employed on the reaction activity have also been discussed. As a result, the relative reactivity among the four insertion reactions should be as follows: H-F > H-OH > H-NH₂ > H-CH₃.     

Probing the imine silylenoid HN=SiNaF and its insertions reaction with R–H (R=F,OH, NH<Subscript>2</Subscript>, CH<Subscript>3</Subscript>) using DFT

The geometries and isomerization of the imine silylenoid HN=SiNaF as well as its insertion reactions with some R–H molecules have been systematically investigated theoretically, where R=F, OH, NH₂, and CH₃, respectively. The barrier heights for the four insertion reactions are 67.7, 115.6, 153.5, and 271.5 kJ/mol at the B3LYP/6-311+G* level of theory, respectively. Here, all the mechanisms of the four reactions are identical to each other, i.e., a stable intermediate has been formed during the insertion reaction. Then, the intermediate could dissociate into the substituted silylene (HN=SiHR) and NaF with a barrier corresponding to their respective dissociation energies. Correspondingly, the reaction energies for the four reactions are 71.8, 95.5, 123.3, and 207.6 kJ/mol, respectively, which are linearly correlated with the calculated barrier heights. Furthermore, the effects of halogen substitutions (F, Cl, and Br) on the reaction activity have also been discussed. As a result, the relative reactivity among the four insertion reactions should be as follows: H–F > H–OH > H–NH₂ > H–CH₃.     

DFT studies of the phosphinidene derivative HPNaF and its insertion reaction with R–H(R=F,OH, NH<Subscript>2</Subscript>, CH<Subscript>3</Subscript>)

The formations of the phosphinidene derivative HPNaF and its insertion reactions with R–H (R=F, OH, NH₂, CH₃) have been systematically investigated employing the density functional theory (DFT), such as the B3LYP and MPW1PW91 methods. A comparison with the results of MP2 calculations shows that MPW1PW91 underestimates the barrier heights for the four reactions considered. Similarly, the same is also true for the B3LYP method depending on the selected reactions, but by much less than MPW1PW91, where the barrier heights of the four reactions are 25.2, 85.7, 119.0, and 142.4 kJ/mol at the B3LYP/6-311+G* level of theory, respectively. All the mechanisms of the four reactions are identical to each other, i.e., an intermediate has been located during the insertion reaction. Then, the intermediate could dissociate to substituted phosphinidane(H₂RP) and NaF with a barrier corresponding to their respective dissociation energies. Correspondingly, the reaction energies for the four reactions are −92.2, −68.1, −57.2, and −44.3 kJ/mol at the B3LYP/6-311+G* level of theory, respectively, where both the B3LYP and MPW1PW91 methods underestimate the reaction energies compared with the MP2 results. The linear correlations between the calculated barrier heights and the reaction energies have also been observed. As a result, the relative reactivity among the four insertion reactions should be as follows: H–F > H–OH > H–NH₂ > H–CH₃.     

Theoretical studies on the imine germylenoid HNGeNaF and its insertion reaction with R-H (R = F, OH, NH2, CH3)

The geometries and isomerization of the imine germylenoid HNGeNaF as well as its insertion reactions with R-H (R = F, OH, NH₂, CH₃) have been systematically investigated at the B3LYP/6-311+G^∗ level of theory. The potential barriers of the four insertion reactions are 117.2, 172.6, 219.7, and 322.3 kJ/mol, respectively. Here, all the mechanisms of the four reactions are identical to each other, i.e., an intermediate has been formed first during the insertion reaction. Then, the intermediate could dissociate into the substituted germylene (HNGeHR) and NaF with a barrier corresponding to their respective dissociation energies. Correspondingly, the reaction energies for the four reactions are 185.0, 208.1, 224.4, and 266.9 kJ/mol, respectively, which are linearly correlated with the calculated barrier heights. Compared with the insertion reaction of HNGe: and R-H, the introduction of NaF makes the insertion reaction occur easily though it is more difficult to proceed than that of insertion reaction between H₂GeNaF and R-H. Furthermore, the effects of halogen (F, Cl, Br) substitution and inorganic salts employed on the reaction activity have also been discussed. As a result, the relative reactivity among the four insertion reactions should be as follows: H-F > H-OH > H-NH₂ > H-CH₃.     

Theoretical Investigation on Mechanism,Thermochemistry, and Kinetics of the Gas-phase Reaction of 2-Propargyl Radical with Formaldehyde

Gas-phase mechanism and kinetics of the reactions of the 2-propargyl radical(H2CCCH), an important intermediate in combustion processes, with formaldehyde were investigated using ab initio molecular orbital theory at the coupled-cluster CCSD(T)//B3LYP/6-311++G(3df,2p) method in conjunction with transition state theory(TST), variational transition state theory(VTST) and Rice-Ramsperger-Kassel-Marcus(RRKM) calculations for rate constants. The potential energy surface(PES) constructed shows that the H2CCCH+HCHO reaction has six main entrances, including two H-abstraction and four additional channels, in which the former is energetically more favorable. The H-abstraction channels slide down to two quite weak pre-complexes COM-01(-9.3 kJ/mol) and COM-02(-kJ/mol) before going via energy barriers of 71.3(T0/P1) and 63.9 kJ/mol(T0/P2), respectively. Two post-complexes, COM-1(-17.8 kJ/mol) and COM-2(-23.4 kJ/mol) created just after coming out from T0/P1 and T0/P2, respectively, can easily be decomposed via barrier-less processes yielding H2CCCH2+CHO(P1,-12.4 kJ/mol) and HCCCH3+CHO(P2,-16.5 kJ/mol), respectively. The additional channels occur initially by formation of four intermediate states, H2CCCHCH2O(I1, 1.1 kJ/mol), HCCCH2CH2O(I3, 4.5 kJ/mol), H2CCCHOCH2(I4, 10.2 kJ/mol), and HCCCH2OCH2(I6, 19.1 kJ/mol) via energy barriers of 66.3, 59.2, 112.2, and 98.6 kJ/mol at T0/1, T0/3, TOM, and TO/6, respectively. Of which two channels producing 14 and 16 can be ignored due to coming over tlie high barriers TOM and TO/6, respectively. The rate constants and product branching ratios for the low-energy channels calculated show that the H2CCCH+HCHO reaction is almost pressure-independent. Altliough the H2CCCH+HCHO→Ⅰ1 and H2CCCH+HCHO→Ⅰ3 channels become dominant at low temperature, however, they are less competitive channels at high temperature.     

CX_2(X=H,F,Cl)与甲基异丙基醚C-H键插入反应的理论研究

用从头计算方法在MP2 /6 31G(d)水平上研究了CX2 (X =H ,F ,Cl)与甲基异丙基醚的C -H键插入反应。CCl2 与甲基异丙基醚两个不同的α C的C -H键插入势垒分别为 117.2kJ/mol (甲基 )和 2 0 .6kJ/mol (异丙基 )。CF2 与异丙基α C的C -H键上插入势垒为 12 0 .0kJ/mol,在插入甲基上C -H键时会引起C -O键的断裂。CH2 的插入反应则不需要势垒。对CX2 与二甲醚、甲乙醚、甲基异丙基醚、甲基苄基醚上各种不同的C -H键插入势垒进行了比较 ,甲基和苯基都促使其毗邻的C -H键更容易被CX2 所插入     

类锗烯H2C=GeLiCl与RH(R=F,OH, NH2)的插入反应

采用DFT B3LYP和QCISD方法研究了不饱和类锗烯H2C=GeLiCl与RH(R=F, OH, NH2)的插入反应. 在B3LYP/6-311+G(d,p)水平上优化了反应势能面上的驻点构型. 结果表明, H2C=GeLiCl与HF、H2O 或NH3发生插入反应的机理相同. QCISD/6-311++G(d,p)//B3LYP/6-311+G(d,p)计算的三个反应的势垒分别为173.53、194.48和209.05 kJ·mol-1, 反应热分别为60.18、72.93和75.34 kJ·mol-1. 相同条件下发生插入反应时, 反应活性顺序都是H—F>H—OH>H—NH2.     

Theoretical Study on Mechanism of Cycloadditional Reaction Between Dichloro-Germylidene and Formaldehyde

Mechanism of the cycloadditional reaction between singlet dichloro-germylidene and formaldehyde has been investigated with MP2/6-31G^* method, including geometry opti-mization, vibrational analysis and energies for the involved stationary points on the poten-tial energy surface. From the potential energy profile, we predict that the cycloaddition reaction between singlet dichloro-germylidene and formaldehyde has two competitive dom-inant reaction pathways, going with the formation of two side products (INT3 and INT4), simultaneously. Both of the two competitive reactions consist of two steps, two reactants firstly form a three-membered ring intermediate INT1 and a twisted four-membered ring intermediate INT2, respectively, both of which are barrier-free exothermic reactions of 41.5 and 72.3 kJ/mol; then INT1 isomerizes to a four-membered ring product P1 via transition state TS1, and INT2 isomerizes to a chlorine-transfer product P2 via transition state TS2,with the barriers of 2.9 and 0.3 kJ/mol, respectively. Simultaneously, P1 and INT2 further react with formaldehyde to form INT3 and INT4, respectively, which are also barrier-free exothermic reaction of 74.9 and 88.1 kJ/mol.