2-噻吩乙酸的低温热容和热力学性质

用精密自动绝热量热计测定了2-噻吩乙酸在78～343 K温区内的摩尔热容. 实验结果表明, 在78～314和337～343 K温区内, 该化合物无相变及其他热异常现象发生, 将实验数据拟合得到了该化合物热容随温度变化的多项式方程; 在314～337 K温区内, 该物质发生固-液熔化相变, 其熔化温度、熔化焓、熔化熵及样品纯度分别确定为: 335.745 K, 16.260 kJ•mol^－1, 48.415 J•K^－1•mol^－1和98.555%. 根据热力学函数关系式, 由热容数据计算出了2-噻吩乙酸在80～340 K温区内相对于标准参考温度298.15 K的热力学函数值.     

纳米氧化锌的低温热容和热力学性质

用扫描电子显微镜(SEM)测定了纳米氧化锌试样的粒径, SEM结果表明ZnO试样平均粒径为30 nm. 在83～350 K温区, 用精密低温绝热量热计测定了ZnO的等压摩尔热容, 拟合出其等压摩尔热容与热力学温度的函数关系式: C_p＝－3.249＋0.2400T－3.413×10^－4T ²＋4.485×10^－7T ³. 根据热容与热力学函数关系, 计算了以298.15 K为基准的纳米ZnO的热力学函数, 并与粗晶ZnO和18 nm ZnO热容文献报导值进行了比较, 从能量角度分析了不同粒径ZnO热容曲线差别产生的原因.     

4-硝基苯甲醇的低温热容和标准摩尔生成焓

用精密自动绝热量热计测定了4-硝基苯甲醇（4-NBA）在78 ~ 396 K温区的摩尔热容。其熔化温度、摩尔熔化焓及摩尔熔化熵分别为:(336.426 ± 0.088) K, (20.97 ± 0.13) kJ×mol-1 和 (57.24 ± 0.36) J×K-1×mol-1.根据热力学函数关系式,从热容值计算出了该物质在80 ~ 400 K温区的热力学函数值 [HT - H298.15 K] 和[ST - S298.15 K]. 用精密氧弹燃烧量热计测定了该物质在T＝298.15 K的恒容燃烧能和标准摩尔燃烧焓分别为 (C7H7NO3, s)＝- ( 3549.11 ± 1.47 ) kJ×mol-1 和 (C7H7NO3, s)＝- ( 3548.49 ± 1.47 ) kJ×mol-1. 利用标准摩尔燃烧焓和其他辅助热力学数据通过盖斯热化学循环, 计算出了该物质标准摩尔生成焓 (C7H7NO3, s)＝- (206.49 ± 2.52) kJ×mol-1 .     

2-甲基-2-丁醇的低温热容和热力学性质

本文用精密自动绝热量热仪测定了2-甲基-2-丁醇在80～305 K温区的热容,从热容曲线(Cp-T) 发现三个固－固相变和一个固－液相变, 其相变温度分别为T = 146.355, 149.929, 214.395, 262.706 K。从实验热容数据用最小二乘法得到以下四个温区的热容拟合方程。在80～140K温区, Cp,m = 39.208 + 8.0724X - 1.9583X2 + 10.06X3 + 1.799X4 - 7.2778X5 + 1.4919X6, 折合温度X = (T –110) / 30; 在 155 ～ 210 K温区, Cp,m = 70.701 + 10.631X + 12.767X2 + 0.3583X3 - 22.272X4 - 0.417X5 + 12.055X6, X = (T –182.5) /27.5; 在220 ～ 250 K温区, Cp,m = 99.176 + 7.7199X - 26.138X2 + 28.949X3 + 0.7599X4 - 25.823X5 + 21.131X6, X = (T – 235)/15; 在 270～305 K温区, Cp,m =121.73 + 16.53 X- 1.0732X2 - 34.937X3 - 19.865X4 + 24.324X5 + 18.544X6, X = (T –287.5)/17.5。从实验热容计算出相变焓分别为0.9392, 1.541, 0.6646, 2.239 kJ×mol-1; 相变熵分别为6.417, 10.28, 3.100, 8.527 J×K-1×mol-1。根据热力学函数关系式计算出80～305 K温区每隔5 K的热力学函数值 [HT –H298.15]和 [ST –S298.15]。     

纳米铁的低温热容和热力学性质研究

用扫描电子显微镜(SEM)测定了纳米铁试样的粒径, SEM结果表明Fe试样平均粒径d为25 nm. 在84～350 K温区, 用精密低温绝热量热计测定了该纳米铁试样的等压摩尔热容, 拟合出其等压摩尔热容与热力学温度的函数关系式: Cp=36.831+14.772x−5.4968x2−0.7099x3−1.3188x4, 其中x=(T−234)/156. 根据热容与热力学函数关系, 计算了以298.15 K为基准的纳米Fe(d=25 nm)热力学函数, 并与文献报导的粗晶Fe及粒径87 nm Fe的热容进行了比较, 从能量角度分析了不同粒径Fe热容曲线差别产生的原因.     

蛋氨酸合成酶催化反应研究 VII.5-氨基-6-甲基尿嘧啶的合成研究

报道了 5 氨基 6 甲基尿嘧啶简便的合成方法 .该化合物以 6 甲基尿嘧啶 ( 2 )为起始物 ,经硝化或重氮化分别得到中间体 5 硝基 6 甲基尿嘧啶 ( 3 )和 5 偶氮苯基 6 甲基尿嘧啶 ( 4 ) ,化合物 3和 4经Na2 S2 O4还原 ,合成产物 5 氨基 6 甲基尿嘧啶 ( 1) .     

尿嘧啶和5-氯尿嘧啶1S0→1S2跃迁动态结构的共振拉曼光谱

采用含时量子波包理论的简单模型对5-氯尿嘧啶和尿嘧啶的共振拉曼光谱开展了强度分析拟合, 获得了1(π, π*)激发态的几何结构变化动态特征. 结果表明, 尿嘧啶1S0→1S2跃迁的动态结构特征因5-位氯原子取代而改变. 5-氯尿嘧啶的动态结构特征主要沿C5=C6伸缩振动+C6H12 弯曲振动和N3H9/N1H7弯曲振动+N1C6伸缩振动反应坐标展开, 而尿嘧啶的动态结构特征主要沿嘧啶环的伸缩振动+C5H11/C6H12/N1H7弯曲振动和C4=O10伸缩振动反应坐标展开. π和π*轨道中氯原子的pz电子参与嘧啶环的p-π共轭作用导致了在1(π, π*)激发态上5-氯尿嘧啶的振动重组能更多地配分给嘧啶环的弯曲振动模式和C5=C6伸缩振动模式. 尿嘧啶在甲醇中的激发态动态结构特征与在水中的基本一致, 但波包沿C5H11/C6H12/N1H7弯曲振动+N1C6伸缩振动(υ12)和环呼吸振动(υ17)反应坐标的运动明显增强.     

苯氧乙酸嘧霉胺盐的低温热容和热力学性质研究

用精密自动绝热量热计测定了苯氧乙酸嘧霉胺盐在81-380 K之间的低温热容. 结果表明, 该化合物在81-328 K之间无相变和热异常现象发生, 在328-354 K之间发生固-液熔化, 其熔化温度、摩尔熔化焓和摩尔熔化熵分别为(349.38±0.03) K, (34.279±10) kJ/mol和(98.13±0.05) J/（K·mol）. 根据热力学函数关系式计算出苯氧乙酸嘧霉胺盐在80-325 K之间以标准状态(298.15 K)为基准的热力学函数值.     

重铬酸钾晶体低温热容及热力学性质的研究

用精密自动绝热量热计测定了重铬酸钾晶体在100～390 K温区内的摩尔热容.实验结果表明在研究温度区间内重铬酸钾无相变和其它热反常现象发生,但其热容在不同的温度范围表现出不同的变化趋势.在100 K≤ T ≤ 275 K和350 K≤ T ≤390 K区间内,其热容随温度的升高明显增大,在275 K≤ T ≤350 K区间,其热容约为定值.将重铬酸钾摩尔热容实验值Cp,m(J•K－1•mol－1)拟合成温度T的多项式方程,在100 K≤ T ≤275 K,为Cp,m=0.0050T2－1.0320T＋125.22； 275 K≤ T ≤ 350 K,为Cp,m=209.37； 350 K≤ T ≤390 K,为Cp,m= 0.0266T2－18.823T＋3542.3.根据热力学函数关系式,从热容值计算出了298.15 K～ 400 K温区范围内每隔5 K的热力学函数值.     

5-氯尿嘧啶质子转移异构化的密度泛函理论研究

采用密度泛函B3LYP/6-311+G**方法,对5-氯尿嘧啶分子内质子转移及水助催化质子转移引起的互变异构反应机理进行了计算研究,获得了互变异构过程的反应焓、活化能、活化吉布斯自由能和质子转移反应的速率常数等参数。计算结果表明,5-氯尿嘧啶无论是孤立分子还是一水合物,其双酮式CU1是最稳定异构体,由双酮式向烯醇式异构化找到3条通道(P1,P2,P3),各通道速控步骤的活化能分别为177.85、177.05和197.58kJ/mol。当水分子参与反应以双质子转移机理异构化时,活化能显著降低,各通道速控步骤的活化能依次降为66.24、69.36和77.85kJ/mol,有利于双酮式向烯醇式或酮醇式转变。计算结果还表明,氢键作用在增大5-氯尿嘧啶一水复合物稳定性、降低质子转移异构化反应活化能等方面起着重要作用。     

Low Temperature Heat Capacities and Thermodynamic Properties of Zinc L-Threonate Zn(C_4H_7O_5)_2(s) by Adiabatic Calorimetry

Low-temperature heat capacities of the solid compound Zn(C4H7O5)2(s) were measured in a temperature range from 78 to 374 K, with an automated adiabatic calorimeter. A solid-to-solid phase transition occurred in the temperature range of 295?322 K. The peak temperature, the enthalpy, and entropy of the phase transition were determined to be (316.269±1.039) K, (11.194±0.335) kJ?mol-1, and (35.391±0.654) J?K-1?mol-1, respectively. The experimental values of the molar heat capacities in the temperature regions o...     

Low-temperature Heat Capacities and Thermodynamic Properties of Solid State Coordination Compound Zn(nicotinate)_2·H_2O(s)

A novel compound—monohydrated zinc nicotinate was prepared via room temperature solid phase synthesis and ball grinding.FTIR,chemical and elemental analyses and X-ray powder diffraction technique were applied to characterizing the structure and composition of the complex.Low-temperature heat capacities of the solid coordination compound were measured by a precision automated adiabatic calorimeter over a temperature range from 77 to 400 K.A solid-solid phase transition process occurred in a temperature range...     

Heat Capacities and Thermodynamic Properties of 3-（2,2-Dichloroethenyl）-2,2-dimethylcyclopropanecarboxylic Acid

The heat capacities of 3 - (2,2-dichloroethenyl) -2,2-dimethylcyclopropanecarboxylic acid ( a racemic mixture,molar ratio of cis-/trans-structure is 35/65) in a temperature range from 78 to 389 K were measured with a precise automatic adiabatic calorimeter. The sample was prepared with a purity of 98.75% ( molar fraction). A solid-liquid fusion phase transition was observed in the experimental temperature range. The melting point, Tm, enthalpy and entropy of fusion, △fusHm, △fusSm, of the acid were determined to be ( 331.48 ± 0.03 ) K, ( 16. 321 ± 0.031 ) kJ/mol,and (49.24 ± 0.19) J/( K·mol), respectively. The thermodynamic functions of the sample, HT - H298.15, ST -S298.15 and GT - G298.15, were reported at a temperature intervals of 5 K. The thermal decomposition of the sample was studied using thermogravimetric (TG) analytic technique, the thermal decomposition starts at ca. 418 K and ends at ca. 544 K, the maximum decomposition rate was obtained at 510 K. The order of reaction, preexponential factor and activation energy are n =0.23, A =7. 3 × 107 min -1, E =70.64 KJ/mol, respectively.     

Low-temperature Heat Capacity and Standard Thermodynamic Functions of D-Galactose and Galactitol

The heat capacities of D-galactose and galactitol were measured on a quantum design physical property measurement system(PPMS) over a temperature range of 1.9―300 K, and the experimental data were fitted to a function of T using a series of theoretical and empirical models in appropriate temperature ranges. The fit results were used to calculate thermodynamic function values,C_p,m^θ,Δ₀^TS_m^θ, and Δ₀^TH_m^θfrom 0 K to 300 K. The standard molar heat capacity, entropy and enthalpy values of D-galactose and galactitol at 298.15 K and 0.1 MPa were determined to be C_p,m^θ =(227.96±2.28) and (239.50±2.40) J·K^-1·mol^-1,S_m^θ= (211.22±2.11) and (230.82±2.30) J·K^-1·mol^-1 and = H_m^θ (33.95±0.34) and (36.57± 0.37) kJ/mol, respectively.     

Synthesis and Biological Evaluation of Novel Uracil and 5-Fluorouracil-1-yl Acetic Acid-Colchicine Conjugate

A series of novel uracil and 5-fluorouracil-1-yl-acetic acid-colchicine derivatives(6a-6n) was synthesized via coupling uracil and 5-fluorouracil(5-FU) with C-10 analogues of colchicine. The antitumor activities of the target compounds against human hepatocellular carcinoma(BEL7402) cells, human ovary carcinoma(A2780) cells, human lung adenocarcinoma(A549) cells and human breast carcinoma(MCF7) cells were tested in vitro, and the structure-activity relationship(SAR) of the compounds was also studied. The bioassay results demonstrate that most of the tested compounds display significant activity and particularly, compounds 6a, 6e, 6h and 6l show more potent cytotoxic activities than 5-fluorouracil and colchicine. The results show that the new derivatives of colchicine are potential suppressors on human cancer.     

N-对甲基苯基-N′-（2-吡啶基）脲的低温热容及热分析

通过低温量热和热分析方法,测定了N-对甲基苯基-N′-（2-吡啶基）脲(以下简称NPMPN′2PU)的低温热容和热力学性质.通过对NPMPN′2PU进行低温量热,得到了NPMPN′2PU在80～370 K 温区的热容曲线,热容曲线光滑,没有任何热异常现象,由此实验热容数据计算出NPMPN′2PU在这段温区内的热力学数据.从DSC实验结果发现, NPMPN′2PU熔化峰值出现在173.86 ℃,熔化焓为204.45 kJ•mol－1.紧接熔化峰后NPMPN′2PU开始分解,分解峰只有一个,分解峰值温度为226.11 ℃.TG和DTG的实验结果表明,NPMPN′2PU失重的峰值为227.2 ℃,这些结果与DSC实验结果吻合.     

右旋布洛芬的低温热容

在80～370 K温度范围内, 用精密自动绝热量热计准确测量了右旋布洛芬的摩尔热容.其固态右旋布洛芬测量值对折和温度X[X=f(T)]的拟和方程为:Cp,m(S)=－39.483X4－66.649X3＋95.196X2＋210.84X＋172.98;相应的液态的拟和方程为 :Cp,m(L)=7.191X3＋4.2774X2＋56.365X＋498.5.并计算得到右旋布洛芬相对于室温(298.15 K)的摩尔焓和摩尔熵.右旋布洛芬的熔点为(324.15±0.02) K.基于摩尔热容的测量,还可获得右旋布洛芬的纯度为99.44％.并对右旋布洛芬和消旋布洛芬的热容进行了对比研究.     

高效热管传热工质的热力学研究

用精密绝热量热法测量了高效热管传热工质在78～320 K温区内的热容.结果表明，在78.41～245.19 K， Cp/(J•K－1•g－1)=0.5369T＋0.07279.在274.08～318.51 K， Cp/(J•K－1•g－1)=3.403±0.020.在245～274 K， 高效热管传热工质发生固液相变.其相变温度、相变焓和相变熵分别是271.21 K、353.6 J•g－1，和1.304 J•K－1•g－1.根据热容与温度的定量关系和热力学函数之间的关系，得到了以标准温度298.15 K为基准的高效热管传热工质的热力学函数.