松香和枞酸在聚乙烯膜上氧化反应动力学研究

设计了松香和枞酸在聚乙烯膜上的氧化反应器, 建立了枞酸在聚乙烯膜上的紫外分光光度分析方法, 跟踪测定了松香和枞酸氧化反应的过程. 实验结果表明, 松香和枞酸的氧化反应均呈现表观一级反应. 枞酸的氧化反应温度为30, 35, 40, 45, 50和55 ℃时, 表观速率常数分别为0.0036, 0.0041, 0.0062, 0.0087, 0.011和0.0157 min^-1, 表观反应活化能Ea为50.29 kJ/mol. 松香的氧化反应温度为35, 40和45 ℃时, 表观速率常数分别为0.0009, 0.0015和0.0025 min^-1 , 表观反应活化能E_a为80.2 kJ/mol.     

微波作用下的多肽固相缩合反应及动力学研究

分别在微波作用以及传统加热两种方式下, 研究了Fmoc-Val-OH与NH₂-Tyr(t-Bu)-Wang树脂的固相缩合反应及其动力学. 测定了温度变化对反应速率的影响, 并获得了两种方式下的缩合反应的宏观动力学参数: 300 W微波作用下表观缩合反应级数为2.3, 活化能为104.7 kJ/mol; 传统方法中表观反应级数为2.9, 活化能为142.4 kJ/mol. 微波作用将常规条件下的连接率由68%提高到95%, 而所需时间降为常规条件的1/14.     

固相合成胸腺五肽(TP5)

采用Fmoc固相多肽合成中的活化酯方法和2,6-二氯苯甲酰氯(DCB)混合酸酐法, 对Fmoc-Tyr(t-Bu)-OH与Wang树脂反应中的反应级数和表观活化能进行了研究, 并采用常规方法和微波强化方法分别进行了胸腺五肽的合成. 实验结果表明, 活化酯方法的反应级数为1.855, 表观活化能15.24 kJ/mol, 混合酸酐法的表观活化能为35.14 kJ/mol. 与传统方法相比, 微波将缩合反应速率提高了30倍以上, 氨基酸过量倍数也从传统的三倍降低到两倍.     

乳液聚合中聚苯胺膜形成的动力学研究

以(NH4)2S2O8(APS)为氧化剂,十二烷基苯磺酸(DBSA)同时为乳化剂和掺杂剂,采用乳液聚合方法制备聚苯胺膜(PANIfilm),用石英晶体微天平(QCM)实时监测聚苯胺膜的形成过程,并对其动力学过程进行研究.结果表明,聚苯胺成膜反应对APS是0.5级,对苯胺是1级,聚苯胺膜增长速率随温度的升高而增加,而聚苯胺膜的最终沉积量却减小,表观活化能Ea=41.15kJ/mol,与均相溶液聚合成膜法的结果相近;随着DBSA浓度的增加,聚苯胺膜增长速率减小,而最终的沉积量增大.     

丙烯酰胺与二甲基二烯丙基氯化铵共聚动力学

采用膨胀计法研究了以过硫酸铵 亚硫酸氢钠为引发剂,丙烯酰胺（AM）和二甲基二烯丙基氯化铵（DMDAAC）在水溶液中的共聚反应动力学,测定了相应的聚合表观活化能、聚合速率方程和单体竞聚率。 结果表明,当AM与DMDAAC摩尔比分别为5∶5、6∶4和7∶3时,表观活化能分别为Ea1=90.61 kJ/mol、Ea2=88.88 kJ/mol和Ea3=85.15 kJ/mol;聚合反应温度为45 ℃下,聚合速率方程分别为Rp1=kc(M)2.84c(IO)0.51·c(IR)0.61,Rp2=kc(M)2.77c(IO)0.51c(IR)0.59和Rp3=kc(M)2.73c(IO)0.50c(IR)0.56;2种单体的竞聚率分别为rAM=6.11,rDMDAAC=0.14。 上述实验结果可从动力学角度为不同阳离子度共聚物Poly(DMDAAC-co-AM)（PDA）聚合反应速率差别及产物特征黏度值差异进行解释。     

纳米白藜芦醇脂质体的物理化学稳定性研究

纳米载药脂质体的物理化学稳定性,是其实际应用中的关键问题。文章采用薄膜旋转蒸发法-超声法制备了白藜芦醇纳米脂质体（RES-Lip）,采用透射电子显微镜观察其微观形貌,并考察RES-Lip的物理化学稳定性。通过电导法测定了RES-Lip的相变温度（Tm）,及其在凝聚过程的凝聚速率常数（Kco）和表观活化能（Eco）;采用动态透析-紫外分光光度法,研究了温度和pH对RES-Lip降解的影响。结果表明,RES-Lip为球形囊泡结构,粒径小于100 nm;RES-Lip的相变温度为64℃;凝聚速率常数Kco随体系温度升高而升高;表观活化能Eco为86.056 kJ/mol;RES-Lip的降解符合一级动力学模型,降解的表观活化能Ea为59.3157 kJ/mol,降解过程是吸热、自发、熵增过程。本实验制备得到的RES-Lip在4℃、pH=7.40的条件下储存,稳定性较好。     

侧链型偶氮聚合物液晶在不同波长激发条件下的光致取向

合成了聚甲基丙烯酸 (6 [4 (4 氰基偶氮苯 )苯氧基 ]己酯 ) (Poly(6 [4 (4 cyanophenylazo)phenoxy]hexylmethacrylate) (PM6ABCN) ) ,采用溶液挥发法在玻璃载片上成膜 ,研究了薄膜样品在Tg 温度以下的光致取向 .用波长分别为 36 6、40 0和 436nm的偏振光照射 ,发现PM6ABCN薄膜的光致取向过程不仅依赖于光的强度 ,还依赖所使用的偏振光的波长 .在低于Tg 的温度下 ,用波长为 40 0nm ,功率为 2 0mW cm2 的光照射 10 0s可以使样品的取向达到饱和 ,而用 36 6nm的光导致的取向程度要小于 40 0nm和 436nm的光 ,因为 36 6nm的光会在稳态时产生更多数目的cis异构体     

二乙基二烯丙基氯化铵均聚及其与丙烯酰胺或丙烯酸共聚动力学研究

采用膨胀计法研究了以过硫酸铵为引发剂,二乙基二烯丙基氯化铵(DEDAAC)在水溶液中的均聚及其与丙烯酰胺(AM)和丙烯酸(AA)共聚动力学,测定了相应的聚合表观活化能;采用元素分析法测定了DEDAAC分别与AM和AA在低转化率下共聚物的组成,并采用氯离子选择性电极法测定了DEDAAC-AM共聚物中的氯离子含量,按Kelen-Tudos方法求得了相应的竞聚率.结果表明,DEDAAC均聚速率方程为RP=k[M]0.99[I]0.76,表观活化能Ea=77.00kJ/mol,说明链终止为单基终止和双基终止并存,引发过程与单体浓度无关;DEDAAC与AM在摩尔比为4∶1时,共聚动力学方程为RP=[M]2.53[I]0.90,表观活化能Ea=67.06kJ/mol,单体竞聚率为rDE=0.31±0.02、rAM=5.27±0.53;DEDAAC与AA在摩尔比为4∶1时,共聚动力学方程为RP=k[M]2.94[I]0.83,表观活化能Ea=70.07kJ/mol,竞聚率为rDE=0.28±0.03、rAA=5.15±0.28;DEDAAC与AM和AA等共聚为非理想共聚,得到的产物均为无规共聚物.     

三价铀在空气中的氧化动力学研究

测定了盐酸介质中铀(Ⅲ)在空气中的氧化速率以及不同条件对氧化速率的影响,得出反应速率方程。反应速率随温度升高而增加,表观活化能为34.3kJ/mol。铀(Ⅲ)在空气中转化为铀(Ⅳ)的反应,可能是一个发生在气液相界面的催化氧化过程。     

二氧化碳-氧化环己烯共聚物的合成和热性能研究

采用三元催化剂(Y(Cl3COO)3-ZnEt2-glycerin)催化二氧化碳与氧化环己烯共聚反应,制备了高分子量二氧化碳与氧化环己烯共聚物(PCHC).8 h内催化剂平均活性达到11.8 kg polymer/mol Zn,PCHC主链上碳酸酯单元含量大于95%,数均分子量达到7.0×104.研究了PCHC的玻璃化转变温度和分子量的关系,当PCHC的数均分子量(Mn)低于8.5×104时,玻璃化转变温度(Tg)随Mn增加而升高;Mn高于8.5×104时,Tg对Mn的依赖性不大.当PCHC的分子量充分高时,其玻璃化转变温度可以达到120℃,PCHC的自由体积特征常数K=1.91×105.研究了聚合物分子量对其热稳定性的影响,结果表明提高分子量有利于提高PCHC的热分解温度.通过实施聚合反应和后处理,三元催化剂转化为相应的金属氧化物(主要为氧化锌)残留在聚合物中,采用Kissinger方法得到纯PCHC(除去金属氧化物)的热分解表观活化能约为199.9 kJ/mol,含金属氧化物(Zn含量4400×10-6)PCHC的热分解表观活化能下降为143.9 kJ/mol.因此氧化锌能够促进PCHC的热降解,减少PCHC中氧化锌的含量有利于改善PCHC的耐热性能.     

Rotational mobility of guest molecules in o-terphenyl below T(g)

An optical anisotropy decay technique for measuring probe rotational times in glassy materials is presented. Rotational times from 10(1.4) to 10(5) s have been obtained for a molecule of 1-naphthyl-azomethoxybenzene (NAMB) in o-terphenyl (OTP) over a temperature range from T(g) +3.5 to T(g) -16.5 K. The rotational diffusion follows the temperature dependence of Debye-Stokes-Einstein down to T(g) -4 K with an activation energy of 320 +/- 30 kJ/mol. Below T(g) -9 K, the temperature dependence of rotation mobility was found to be much weaker with an activation energy of 70 +/- 15 kJ/mol.     

高级量子化学从头计算法研究N2和H2O分子间相互作用

在MP2/6-311++G(3d,3p)电子相关校正水平上,对N₂和H₂O分子间可能存在的氢键复合物进行全自由度能量梯度优化,发现了一个接近于直线的弱氢键总能量极小结构(1),进一步在高级电子相关校正的MP4SDTQ和CCSD(T)水平,用6-311++G(3d,3p)基组加上(3s3p2d1f)键函数,用MP4和CCSD(T)计算的结构1的结合能分别为-5.061kJ/mol和-4.715kJ/mol.     

Theoretical Studies on the Mechanism of Photocycloaddition Reaction Between 6 Azauracil and Acetone

The mechanism of photocycloaddition reaction between 6-azauracll and acetone was studied by using semiemptrical SCFMO AMI method. It was found that this reaction is not a concerted one. The calculated results are as follows:(1) A T1 state exciplex is on the T1 state energy surface; (2) T exciplex as a reactant will proceed along the energy surface of T1 state to form a diradical intermediate. The energy barrier of this reaction step is 63. 6 kJ/mol; (3) The T1 state diradical intermediate happens to be close in energy to the ground state intermediate with a similar geometry. Such a situation turns out to be very favorable for an intersystem crossing (jump from the T, state to the ground state) ; (4) The final product will be formed from the ground S0 state intermediate via an energy barrier 88. 2 kJ/mol.     

Ab initio study on the mechanism of reaction HNCO+NH_2

Ab initio UMP2 and UQCISD(T) calculations, with 6-311G** basis sets, were performed for the titled reactions. The results show that the reactions have two product channels: NH2+ HNCO→NH3+NCO (1) and NH2+HNCO-N2H3+CO (2), where reaction (1) is a hydrogen abstraction reaction via an H-bonded complex (HBC), lowering the energy by 32.48 kJ/mol relative to reactants. The calculated QCISD(T)//MP2(full) energy barrier is 29.04 kJ/mol, which is in excellent accordance with the experimental value of 29.09 kJ/mol. In the range of reaction temperature 2300-2700 K, transition theory rate constant for reaction (1) is 1.68 × 1011- 3.29 × 1011 mL · mol-1· s-1, which is close to the experimental one of 5.0 ×1011 mL× mol-1· s-1 or less. However, reaction (2) is a stepwise reaction proceeding via two orientation modes, cis and trans, and the energy barriers for the rate-control step at our best calculations are 92.79 kJ/mol (for cis-mode) and 147.43 kJ/mol (for trans-mode), respectively, which is much higher than     

Predicted thermochemistry and unimolecular kinetics of nitrous sulfide

The geometry of N(2)S was obtained at the CCSD(T)/aug-cc-pV(T + d)Z level of theory and energies with coupled-cluster single double triple (CCSD(T)) and basis sets up to aug-cc-pV(6 + d)Z. After correction for anharmonic zero-point energy, core-valence correlation, correlation up to CCSDT(Q) and relativistic effects, D(0) for the N-S bond is estimated as 71.9 kJ mol(-1), and the corresponding thermochemistry for N(2)S is Δ(f)H(0)(°)=205.4 kJ mol(-1) and Δ(f)H(298)(°)=202.6 kJ mol(-1) with an uncertainty of ±2.5 kJ mol(-1). Using CCSD(T)/aug-cc-pV(T + d) theory the minimum energy crossing point between singlet and triplet potential energy curves is found at r(N-N) ≈ 1.105 ? and r(N-S) ≈ 2.232 ?, with an energy 72 kJ mol(-1) above N(2) + S((3)P). Application of Troe's unimolecular formalism yields the low-pressure-limiting rate constant for dissociation of N(2)S k(0) = 7.6 × 10(-10) exp(-126 kJ mol(-1)/RT) cm(3) molecule(-1) s(-1) over 700-2000 K. The estimated uncertainty is a factor of 4 arising from unknown parameters for energy transfer between N(2)S and Ar or N(2) bath gas. The thermochemistry and kinetics were included in a mechanism for CO/H(2)/H(2)S oxidation and the conclusion is that little NO is produced via subsequent chemistry of NNS.     

Crystallization at the glass transition in supercooled thin films of methanol

The stability of an amorphous material depends on how fast and by what mechanism crystallization occurs. Based on crystallization rate measurements through optical reflectivity changes in supercooled methanol thin films, it is observed for the first time that there is a definitive and detectable change of the crystallization mechanism at the glass transition temperature T(g). For methanol glasses below T(g)=103.4 K, crystallization occurs as an interface controlled, one-dimension process at frozen-in embryo sites, while in the deep supercooled liquid phase above T(g) crystallization is diffusion controlled in two dimensions with a constant nucleation rate and an activation energy of 107.8(+/-4.7) kJ/mol.     

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.     

3,6-二羟基哒嗪质子转移过程的理论研究

为了探索3,6-二羟基哒嗪分子醇式和酮式结构互变异构化的反应机理,本研究组采用DFT B3LYP/6-311+G(d)方法对标题化合物异构化反应的势能面进行了研究,在探讨各种可能的反应途径中,发现至少有34种异构体和43种过渡态.结果表明,6-羟基-3(2H)-哒嗪酮不论是单体,与水形成配合物,还是二聚体,比其相对应的异构体能量低,表明在通常情况下是以6-羟基-3(2H)-哒嗪酮形式稳定存在的,这与前人通过实验数据对互变异构体的比率进行预测的结果是一致的;在考察的可能反应途径中,直接进行的分子内质子转移过程需要的活化能为142.2 kJ·mol^-1,水助催化时,反应活化能为41.3 kJ·mol^-1,考虑溶剂效应后,其活化能为59.2 kJ·mol^-1,二聚体双质子转移的活化能为16.8 kJ·mol^-1,二聚体双质子转移所需活化能最低,在室温下就可以进行.由此可见氢键在降低反应活化能方面起着重要的作用.     

The dynamical properties of the aromatic hydrogen bond in NH4(C6H5)4B from quasielastic neutron scattering

NH(4)(C(6)H(5))(4)B represents a prototypical system for understanding aromatic H bonds. In NH(4)(C(6)H(5))(4)B an ammonium cation is trapped in an aromatic cage of four phenyl rings and each phenyl ring serves as a hydrogen bond acceptor for the ammonium ion as donor. Here the dynamical properties of the aromatic hydrogen bond in NH(4)(C(6)H(5))(4)B were studied by quasielastic incoherent neutron scattering in a broad temperature range (20< or =T< or =350 K). We show that in the temperature range from 67 to 350 K the ammonium ions perform rotational jumps around C(3) axes. The correlation time for this motion is the lifetime of the "transient" H bonds. It varies from 1.5 ps at T=350 K to 150 ps at T=67 K. The activation energy was found to be 3.14 kJ mol, which means only 1.05 kJ mol per single H bond for reorientations around the C(3) symmetry axis of the ammonium group. This result shows that the ammonium ions have to overcome an exceptionally low barrier to rotate and thereby break their H bonds. In addition, at temperatures above 200 K local diffusive reorientational motions of the phenyl rings, probably caused by interaction with ammonium-group reorientations, were found within the experimental observation time window. At room temperature a reorientation angle of 8.4 degrees +/-2 degrees and a correlation time of 22+/-8 ps were determined for the latter. The aromatic H bonds are extremely short lived due to the low potential barriers allowing for molecular motions with a reorientational character of the donors. The alternating rupture and formation of H bonds causes very strong damping of the librational motion of the acceptors, making the transient H bond appear rather flexible.