醇溶剂对羰基(C=O)紫外吸收的定量影响

以各种醇为溶剂测定了丙酮和环己酮的羰基紫外吸收能量ΔE,讨论了ΔE与醇分子结构的关系。结果表明ΔE与醇分子中烷基的极化效应指数PEI有良好的线性关系:ΔE=a+bPEI。     

基于铝氟配位反应的动力学-电位法对铝的测定

以氟离子选择性电极作指示电极,用动力学电位法对铝的测定进行了研究.在低pH条件下,铝氟反应E～t曲线的斜率△E/△t与铝的浓度cAl成正比.实验步骤为:第一步,根据铝的校正溶液与氟反应的△E/△t,作出△E/△t～cAl工作曲线;第二步,根据铝试液与氟反应的△E/△t,求出铝的浓度.合适的实验条件是:pH范围1～2;温度范围288～303 K;铝的浓度范围1×10-3～5×10-2mol/L;加入的氟的浓度范围5×10-4～5×10-2mol/L.此外,对动力学电位法测定铝的计算式进行了理论推导,对该法存在的问题、可以采取的措施及误差的分布进行了讨论.     

Yb3+在不同基质中基态分裂能的计算分析

利用晶体场理论,推导出Yb3+离子基态(2F7/2)与Nd3+离子基态(4I9/2)最大分裂能之间的关系式为△E(2F7/2)=1.4667△E(4I9/2),从实验数据拟合得到的关系式为△E(2F7/2)=1.0987△E(4I9/2).理论计算与实验拟合存在差异,分析了出现差异的原因,认为差异主要是由相同晶体场对于不同掺杂离子的影响即晶体场参数Nv值不完全相同而引起的.     

一种镍的二胺和β-二酮混合配体配合物在不同醇中热致-溶致变色行为的可见光谱研究

用可见光谱法对一种Ni(II)的二胺和β-二酮类混合配体配合物([Ni(II)(Me4en)(acac)]ClO4)在四种醇类溶剂中所形成的正方平面体和变形八面体物种的平衡过程进行了研究. 通过对配合物在醇中的热致-溶致变色光谱曲线的分峰拟合处理, 计算出了这一过程的平衡常数, 焓变△H和熵变△S等热力学函数, 同时, 得到了正方平面体和变形八面体物种各自的光谱吸收曲线. △H数据表明, 在醇中形成变形八面体物种是一个放热过程, 放热量的大小反映了醇分子与配合物中心离子Ni(II)配位能力的强弱. △S的绝对值与中心离子Ni(II)配位的或释放的醇分子数相关. 计算结果对深化认识Ni(II)的二胺和β-二酮类混合配体配合物热致变色的本质有所帮助.     

一种镍的二胺和β-二酮混合配体配合物在不同醇中热致-溶致变色行为的可见光谱研究

用可见光谱法对一种Ni(Ⅱ)的二胺和β-二酮类混合配体配合物([Ni(Ⅱ)(Me4en)(acac)]ClO4)在四种醇类溶剂中所形成的正方半面体和变形八面体物种的平衡过程进行了研究.通过对配合物在醇中的热致-溶致变色光谱曲线的分峰拟合处理,计算出了这一过程的平衡常数,焓变△H和熵变△S等热力学甬数,同时,得到了正方平面体和变形八面体物种各自的光谱吸收曲线.△H数据表明,在醇中形成变形八面体物种是一个放热过程,放热量的大小反映了醇分子与配合物中心离子Ni(Ⅱ)配位能力的强弱.△S的绝对值与中心离子Ni(Ⅱ)配位的或释放的醇分子数相关.计算结果对深化认识Ni(Ⅱ)的二胺和β-二酮类混合配体配合物热致变色的本质有所帮助.     

苯基在联苯亲电取代反应中的定位作用

运用G03程序,在HF/6-31G基组水平,分析了苯基（RPh）在联苯类化合物（RPh-Ph,R：NH2,CH3,OH,Br,H,CHO,CN,COOH,NO2）亲电取代反应中的定位作用。联苯和取代联苯的构象分析表明,联苯和间、对位取代联苯的碳-碳单键旋转的能垒很小,约12 kJ/mol,邻取代联苯的碳-碳单键旋转能垒△E（R）较大,且△E（COOH） > △E（NO2） > △E（CHO） > △E（CH3） > △E（NH2） > △E（OH） > △E（Br） > △E（CN）,因此,邻位取代基的空间效应较大,碳-碳单键旋转受阻。联苯和取代联苯的原子电荷分布随它们的构象改变而变化,在同一联苯或取代联苯化合物的最低能稳定结构中,无论取代基R为第一类还是第二类定位基,未取代苯环的碳原子总电荷密度比取代苯环碳原子的总电荷密度大,亲电取代反应将选择在未取代的苯环上发生;未取代苯环的邻位碳原子电荷密度较低、空间效应较大,而对位碳原子的电荷密度较大,亲电取代反应难以在该环的2,6-位（邻位）发生,将选择在该苯环的对位发生。因此,取代苯基（RPh-）在联苯的亲电取代反应中主要表现为对位定位基。     

不受电极斜率限制的离子电极标准加入法算图

格兰图在离子选择电极法中应用广泛,但该图要求电极响应的能斯特斜率为一定值。对电极斜率偏离理论值的情况进行修正已有报道。 本文提出一种不需任何电极斜率校正步骤的算图,即以加入标准溶液后电位的变化值△E与实际斜率S的比值△pe对加入标准溶液体积Vs作图的计算图(简称为△pe格兰图)。在实际操作中,根据测得的△E值和S值,经换算为△pe后,即可在标准算图上作图进行结果计算。克服了作空白溶液线或共线图线时可能引进的误差,简化了结果处理过程。此外,对不同价态离子的测定,该算图纵坐标标度△pe不变,不必扩大或缩小,作图十分方便。     

非离子型表面活性剂组成的微乳液热力学性质 (IV) 烷烃的碳原子数影响

由表面活性剂、醇、油和水所组成的微乳液,油相的烷烃长度会影响到微乳液的性质,主要表现在界面相组成和界面张力.Birdi 用加溶法研究以十六烷、硬脂酸钠、水和醇(从C_5到C_9)所组成的微乳液,醇的碳原子数n_a 与标准自由能△G(?)有以下关系:△G(?),醇=1563-839.5n_a(J·mol~(-1)在同样体系内,戊醇和不同烷烃则:     

十二烷基磺酸钠体系形成胶束的热力学研究

本文采用电导法和量热法,在40℃时系统地测定了十二烷基磺酸钠在水溶液中、以及在各种添加物(短链醇、氯化钠)存在时形成胶束的热力学函数(△G_m~、△H_M~、△S_m~.讨论了添加物对十二烷基磺酸钠胶束形成的热力学函数的影响.     

超酸POSA催化酯化反应动力学及线性自由能关系

全氟辛基磷酸(C_8F_(17)SO_3H,Perfluorooctanesulfonic acid,POSA)是熔点为90℃的固体超酸.我们首次测得其酸度函数值是-12.11±0.03,并将其用于催化Friedel-Crafts烃基化反应和醇脱水制烯,取得了良好的结果.本文报导我们研究POSA催化酯化反应的动力学和线性自由能关系. 线性自由能关系是研究反应动力学微观过程的有效方法之一.对反应速度常数、平衡常数的测定,对于活化参数△E、△S、△H的计算以及反应机理的深入了解都是非常有用的.近年报导的Wittig反应线性自由能关系的研究即是一例. 我们测定了POSA催化对位取代苯甲酸的乙酯化反应的速率常数k,计算了反应的活化能     

Alcohol and proton transport in perfluorinated ionomer membranes for fuel cells

To clarify the transport mechanisms of alcohols and proton in perfluorosulfonated ionomer (PFSI) membranes for fuel cells, four membranes having different equivalent weight (EW) values were examined. Membranes were immersed in methanol, ethanol, and 2-propanol to prepare a total of 12 samples, and membrane swelling, mass (alcohol and proton) transports, and interactions between alcohols and proton were investigated systematically in the fully penetrated state. The membrane expansion fraction theta and alcohol content lambda increased with decreasing the EW value for all the samples. The self-diffusion coefficients (D's) of the alkyl group and of OH (including protons) were measured separately by the pulsed-gradient spin-echo (PGSE)-NMR method and the D's also increased with decreasing the EW value. These results implied that the alcohols penetrate into the hydrophilic regions of the PFSI membranes and diffuse through the space expanded by the alcohols. The ionic cluster regions formed by the alcohols resemble those induced by water in the water swollen membrane, where protons dissociated from sulfonic acid groups transport through the regions together with water molecules. The D values decreased with increasing the molecular weight of alcohols. This trend was supported by activation energies Ea estimated from the Arrhenius plots of D in the temperature range from 30 to -40 degrees C. The PGSE-NMR measurements also revealed that protons move faster than the alkyl groups in the membranes. The proton transport by the Grotthuss (hopping) mechanism was facilitated by the increase of the alcohol content and the decrease of the molecular weight. This result was also supported by the experimental results of proton conductivity kappa and mobility u(H(+)). Density functional theory (DFT) calculations of the interaction energy DeltaE(int) between proton and alcohol (including OH) showed that the /DeltaE(int)/ increases with increasing the molecular weight of alcohols, which is in a inverse relationship with the kappa and u(H(+)) values. The proton transport depends strongly on the DeltaE(int) in the membranes.     

醇和N,N-二甲基乙酰胺分子间相互作用的FTIR光谱研究

The association between alcohols and N,N-dimethylacetamide in carbon tetrachloride was investigated using FTIR spectroscopy at 298 K.The formation constants for 1∶1 and 1∶2 complexes were calculated using the method of Whetsel and Kagarise.The observed 1∶1 complex values were also verified using the method of Nash.The rate of change in C=O bond moment on complexing with alcohols increased with increasing acidity of alcohols.The formation constant and values of free energy change increased with the increase in carbon chain length of alcohols,which suggested that the degree of complex formation varied with the length of the carbon chain of alcohols.     

An evaluation of solvent mediators for ion-selective electrode membranes based on calcium bis(dialkylphosphate) sensors trapped in poly(vinyl chloride) matrices

This study on several alkan-1-ols, di-n-octylphenyl phosphorate and di-n-nonyl phthalate as solvent materials in ion-selective electrode membranes based on calcium bis(dialkylphosphate) sensors trapped in a PVC matrix indicates that the best electrodes are made with di-n-octylphenyl phosphonate. These are selective for calcium. The liquid alcohols readily exude from the PVC matrix, and solid alcohols are completely unsuitable for membrane fabrication. However, despite a tendency to be exuded, decan-1-ol gives acceptable electrodes responsive to bivalent cations if calcium bis (di-2-ethylhexylphosphate) is used as sensor. Several selectivity coefficients, k(caj), greater than unity were found, but though such values for j = Na or K do not involve complete loss of selectivity towards calcium, a value of K(CaCu) = 13 for a membrane with di-n-nonyl phthalate as mediator and calcium bis(di-n-decylphosphate) as sensor indicates greater selectivity for copper than for calcium.     

Zeeman原子吸收光谱分析法中谱线轮廓的研究Ⅱ.ZAAS法中Rz值研究

报道依据原子吸收光谱(AAS)法的基础,即谱线轮廓间重叠关系图,和Rz的定义,对常用的38条谱线的R~z~(~a~c~)和R~z~(~d~c~)进行了理论计算, 并与相应的实验数据作了对比分析研究两者差值在10%的谱线数目,R~z~(~a~c~)为33条,R~z~(~d~c~)为22条.     

Practical calculation of molecular acidity with the aid of a reference molecule

A set of linear free energy models are presented for determining the pK(a) values of amines, alcohols, and carboxylic acids. Models are determined from a series of pK(a) predictors, taken both from traditional natural atomic orbital analysis (NAO) and from a novel approach introduced here of using a reference molecule: an ammonium ion for amines and a hydrogen sulfide molecule for alcohols and carboxylic acids. Using these reference molecules, we calculate the barrier to proton transfer and show that a number of properties associated with the transition state are correlated with the pK(a). By considering 38 predictors, we obtain a four-variable model for amines and a three-variable model for oxygen-containing compounds. The model for amines is based on 145 compounds and has a root mean squared error (RMSE) of 0.45 and R(2) = 0.98. The oxygen set has 48 molecules: RMSE = 0.26, and R(2) = 0.993. Similar, linear, and multilinear models are constructed after separating the sets into chemically similar categories: alcohols, carboxylic acids, and primary, secondary, tertiary, and aromatic amines. This separation gives simpler models with relatively low RMSE values, where the most important predictor of the pK(a) is the difference in energy between transferring the proton from the reference molecular base to the conjugate acid from the data set.     

Dielectric Dispersion and Electric Relaxation Processes Induced by Ionic Conduction in Formamide, 2-Aminoethanol and Their Binary Mixtures

The complex dielectric permittivity, ionic conductivity, electric modulus and impedance spectra of the dipolar molecules formamide (FA), 2-aminoethanol (AE) and their binary mixtures were investigated in the frequency range from 20 Hz to 1 MHz at 303.15 K. Debye-type distributions of the frequency dependent electric modulus and complex impedance were found, corresponding to an ionic conduction relaxation process in the upper frequency regime of the spectra, whereas a spike in the impedance spectra at low frequencies confirms the contribution of an electrode polarization (EP) relaxation process induced by ionic conduction. Due to the high static permittivity of FA, its ionic conductivity was found more than one order of magnitude higher than that of the AE, which is also shown by the comparative values of their EP and ionic conductivity relaxation times. The dependences of dc ionic conductivity values of the binary mixtures on their relaxation times and static permittivity were explored. The concentration dependent static permittivity and the relaxation times led us to infer the formation of a 1:1 H-bonded stable complex between FA and AE molecules with reduction in the number of effective parallel-aligned dipoles.     

用吸附数据对硅胶表面的分形分析

根据一种中孔硅胶对甲酸、乙酸、丙酸和四氯化碳蒸气吸附等温线的单层区域和毛细凝结区域的数据以及自四氯化碳稀溶液中吸附系列脂肪醇的结果计算了该硅胶表面分形维数D.除了由吸附四氯化碳等温线毛细凝结区域所得D值低于2外,由其它吸附数据得出的该硅胶的分维D近似相等(D=2.06±0.05).中孔硅胶低D值可用其孔结构特性解释.     

Mechanistic investigations of the palladium-catalyzed aerobic oxidative kinetic resolution of secondary alcohols using (-)-sparteine

The mechanistic details of the Pd(II)/(-)-sparteine-catalyzed aerobic oxidative kinetic resolution of secondary alcohols were elucidated, and the origin of asymmetric induction was determined. Saturation kinetics were observed for rate dependence on [(-)-sparteine]. First-order rate dependencies were observed for both the Pd((-)-sparteine)Cl(2) concentration and the alcohol concentration at high and low [(-)-sparteine]. The oxidation rate was inhibited by addition of (-)-sparteine HCl. At low [(-)-sparteine], Pd-alkoxide formation is proposed to be rate limiting, while at high [(-)-sparteine], beta-hydride elimination is proposed to be rate determining. These conclusions are consistent with the measured kinetic isotope effect of k(H)/k(D) = 1.31 +/- 0.04 and a Hammett rho value of -1.41 +/- 0.15 at high [(-)-sparteine]. Calculated activation parameters agree with the change in the rate-limiting step by increasing [(-)-sparteine] with DeltaH(++) = 11.55 +/- 0.65 kcal/mol, DeltaS(++) = -24.5 +/- 2.0 eu at low [(-)-sparteine], and DeltaH(++) = 20.25 +/- 0.89 kcal/mol, DeltaS() = -5.4 +/- 2.7 eu at high [(-)-sparteine]. At high [(-)-sparteine], the selectivity is influenced by both a thermodynamic difference in the stability of the diastereomeric Pd-alkoxides formed and a kinetic beta-hydride elimination to maximize asymmetric induction. At low [(-)-sparteine], the selectivity is influenced by kinetic deprotonation, resulting in lower k(rel) values. A key, nonintuitive discovery is that (-)-sparteine plays a dual role in this oxidative kinetic resolution of secondary alcohols as a chiral ligand on palladium and as an exogenous chiral base.     

醇类化合物气相色谱保留指数的分子拓扑研究

分子中原子i的特征值(ti)定义为tj＝1 ∑hi。并计算了醇类化合物的氢连接性指数，藉助多元线性回归技术分别建立了25个醇类化合物的指数与这些物质的气相色谱保留指数的定量结构／性质相关关系模型。模型具有良好的稳定性和预测能力，氢连接性指数能较好地反映化合物的结构特征。