计算多元酸溶液PH和δi的新公式

对一个n元弱酸,令x=K_1/[H~+](1)K_1为酸的一级离解常数。那么pH=pK_1-px (2)于是,经过变量代换,pH 计算问题转化为对 x的计算。n 元弱碱可按类似方法处理。下面仅就多元酸的情形进行讨论。     

渐进因子分析－pH－分光法测定多元酸的离解常数

根据多元酸平衡体系中型体具有先出现先消失的特点,提出了用渐进因子分析与化学平衡结合迭代,从pH-分光矩阵中求解多元酸离解常数的新方法。用该法测定了多元酸茜素S和铬天青S的离解常数,并讨论了确定型体存在区域的经验式。结果表明该方法稳定、可靠、算法收敛快,所测得的离解常数与文献值吻合。     

渐进因子分析—PH—分光法测定多元酸的离解常数

根据多元酸平衡体系中型体具有先出现先消失的特点，提出了用渐进因子分析与化学平衡结合迭代。从ＰＨ－分光矩阵中解多元酸离解常数的新方法。用该法测定了多元酸茜素Ｓ和铬天青Ｓ的离解常数，并讨论了确定型体存在区域的经验式。结果表明该方法稳定，可靠、算法收敛快、所测得的离解常数与文献值吻合。     

智能求解未知多元酸各级离解常数的研究

本文介绍了一种新的测定未知多元酸各级离解常数的通用方法。该方法实验上采用苛性碱电势滴定多元酸,计算上采用Gordon数学模型和单纯形最优化方法。并为此编制了一名为"GORDANACID"的计算机程序。     

半胱胺-Zn(Ⅱ)络合反应稳定性及热力学特征研究

采用pH电位滴定法,于温度25℃条件下,获取半胱胺盐酸盐的各级加质子常数(lgK_1~H=10.92,lgK_2~H=8.25)、离解常数(K_(a1)=5.62E-09,K_(a2)=1.20E-11)及其与Zn(Ⅱ)形成配合物的稳定常数(lgk5=36.74)、热力学函数(△rHm=-157.14kJ/mol,△rSm=176.74J/(mol·K),△_rGm=-209.60kJ/mol),并计算各pH条件下半胱胺盐酸盐与Zn(Ⅱ)配合的条件稳定常数。计算得Zn(Ⅱ)与半胱胺盐酸盐配位反应的热力学函数△rGm0、△rHm0、△rSm0,证明反应过程为自发放热。半胱胺盐酸盐与Zn(Ⅱ)形成配合物的稳定常数和条件稳定常数均很大,表明形成的半胱胺锌很稳定。     

等色点光度法指示剂类多元酸离解常数的测定—铬天青S

光度法指示剂类多元酸离解常数的测定,当各级离解态的光谱差别甚小,或光谱既有红移又有紫移时,往往不易获得准确的结果。常见的铬天青S即具有上述性质。我们以此为例,利用它在不同pH时吸收光谱先后出现的三个等色点,判明了它的反应历程,并据此拟定了一个测定离解常数的方法,获得的结果比较令人满意。实验仪器:日本岛津UV-240分光光度计;日本东亚HM-20E型酸度计。     

金属离子酸的离解常数与金属离子存在下滴定游离酸的理论处理

金属离子酸的离解常数可推导为Ka=Kw·K_(MOH)及Ka_n=Kw·K_(M(OH)n)。在金属离子存在下滴定游离酸,可以作为混合酸进行理论处理,使用相同的滴定条件与等当点pH计算公式。在加入掩蔽剂滴定时,可以使用金属离子酸的条件稳定常数作出相似的理论处理。     

忽略第二级离解的判据推导和二元弱酸溶液氢离子浓度的近似计算*

为推导出忽略二元弱酸$H_{2}A$第二级离解的判据,设计了虚拟酸A和虚拟酸B并计算了酒石酸、虚拟酸A和虚拟酸B的准确氢离子浓度$[H^{+}]_{T}$和近似氢离子浓度$[H^{+}]_{AV}$。计算结果表明:忽略$H_{2}A$第二级离解的判据与$\frac{K_{a1}}{K_{a2}}$比值相关。从极端二元酸($K_{a1}=K_{a2}$)得到的判据为$\frac{2K_{a2}}{[H^{+}]_{AV}}为推导出忽略二元弱酸H_2A第二级离解的判据,设计了虚拟酸A和虚拟酸B并计算了酒石酸、虚拟酸A和虚拟酸B的准确氢离子浓度[H~+]_T和近似氢离子浓度[H~+]_(AV)。计算结果表明:忽略H_2A第二级离解的判据与■比值相关。从极端二元酸(K_(a1)=K_(a2))得到的判据为■,其中[H~+]_(AV)=■。■≤0.11判据具有广泛的普适性,可以用于所有二元弱酸溶液。新判据除了保证溶液氢离子浓度近似值[H~+]_(AV)的准确度外(误差SymbolqB@5%以内),同时还具有覆盖浓度区间宽的显著优点。     

氯仿溶剂中二氯化钯(Ⅱ)、二正辛基亚砜平衡体系的研究

本文通过紫外光谱法及萃取研究,讨论了二氯二正辛基亚砜合钯(Ⅱ)配合物[Pd(DOSO)_2Cl_2]在氯仿溶剂中的离解平衡: Pd(DOSO)_2Cl_2(?)Pd(DOSO)Cl_2 DOSO Pd(DOSO)Cl_2(?)PdCl_2 DOSO 并测定了25℃时的离解常数K_1=(2.0±0.3)×10~(-3),K_2=(1.3±0.1)×10~(-4)     

配位化合物中的线性热力学函数关系——α-氨基酸、邻菲啰啉合铜(Ⅱ)混型配合物中的线性自由能、线性焓及线性熵关系

用pH电位法及温度系数法证实了混型配合物α-氨基酸-邻菲哕啉-铜(Ⅱ)中的线性自由能、线性焓及线性熵关系。 (一)实验部分 pHS-3型酸度计、501型超级恒温器及恒温滴定池、50μl微量进样器,酸度计、温度计、移液管及容量瓶等均经过校正,邻菲哕啉(Phen)为分析纯试剂,实验的操作方法及铜离子标准溶液的测定参见前文,配体α-氨基酸(αA)的提纯及其离解常数的测定和计算已有报道,若以HL代表氨基酸,其离解常数K_1和K_2分别为     

在强酸与多元酸混合酸中影响各组分酸含量测定的因素及条件

在前文中曾提出，第一终点ＰＨ＞３．７的情况下，以多元酸标准溶液的半中和点为第一点，测定各组分酸含量的方法。在此基础上，本文在理论上明确了影响各组分酸含量测定的因素，从而提出第一终点ＰＨ不同的情况下，Ｋａ１／Ｋａ２倍数不同时可准确滴定的Ｖｅ２／Ｖ＾Ｔｅ值的计算方法。实验结果表明，在此条件下结果是可靠的。     

Local acid environment in poly(ethylene‐ran‐methacrylic acid) ionomers

The local environment of unneutralized carboxylic acid groups in poly(ethylene‐ran‐methacrylic acid) (E/MAA) ionomers neutralized with monovalent (Li and Na) and divalent (Ca and Zn) ions has been investigated with Fourier transform infrared spectroscopy. These unneutralized acid groups interact with one another to form acid dimers, and they associate with existing neutralized complexes. At room temperature, no free acids can be detected for any system, not even for pure E/MAA. With the acid dimer peak (1700 cm^?1) and a known unneutralized acid concentration, the concentration of acids associated with a neutralized complex can be determined. This concentration of associated acids increases with increasing neutralization, reaches a maximum below 50% neutralization, and then decreases toward zero near 80% neutralization. This behavior is perhaps due to the increased driving force for aggregation of the neutralization acids. Although Li, Na, and Ca contain similar concentrations of associated acids over the range of neutralizations, the Zn system contains far fewer associated acids (i.e., more acid dimers) at any particular neutralization level. These results are confirmed by an analysis of the absorbance in the neutralized region (1650–1500 cm^?1). © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2833–2841, 2002     

Determination of acid/base dissociation constants based on a rapid detection of the half equivalence point by feedback-based flow ratiometry.

Acid dissociation constants (Ka) were determined through the rapid detection of the half equivalence point (EP1/2) based on a feedback-based flow ratiometry. A titrand, delivered at a constant flow rate, was merged with a titrant, whose flow rate was varied in response to a control voltage (Vc) from a controller. Downstream, the pH of the mixed solution was monitored. Initially, Vc was increased linearly. At the instance that the detector sensed EP1/2, the ramp direction of Vc changed downward. When EP1/2 was sensed again, Vc was increased again. This series of process was repeated automatically. The pH at EP1/2 was regarded as being pKa of the analyte after an activity correction. Satisfactory results were obtained for different acids in various matrices with good precision (RSD approximately 3%) at a throughput rate of 56 s/determination.     

New approach to (−)-polyoxamic acid and 3,4-diepipolyoxamic acid from d-lyxono-1,4-lactone

The non-natural enantiomer of polyoxamic acid (1) and 3,4-diepipolyoxamic acid (2) was synthesized in four steps from d-lyxono-1,4-lactone (4). Regioselective bromination of unprotected d-lyxono-1,4-lactone with HBr/AcOH led to 2-bromo-2-deoxy-d-xylono-1,4-lactone (5). This intermediate was treated with NaN₃ to give 2-azido-2-deoxy-d-lyxono and xylono-1,4-lactones. Saponification of the obtained 2-azido derivatives gave the corresponding 2-azido-2-deoxyaldonic acids salt which, after neutralization followed by reduction, led to the expected compounds: (−)-polyoxamic acid (3) and 3,4-diepipolyoxamic acid (2) in 38% and 29% overall yields.     

多元弱酸及两性物质逐级稳定常数的pH法测定和计算机优化算法

本文由ｐＨ滴定法原理导出多元弱酸及两性物质逐级稳定常数ｋ＿ｉ的计算公式。编辑了由Ｍｏｎｔｅ－Ｃａｒｌｏ法确定初值，Ｈｏｏｋｅ－Ｊｅａｖｅｓ法精解的计算程序。由此算法测定了方酸及其衍生物的各级稳定常数。结果表明，该法实验简便，数值运算效率高，结果可靠     

Triphenylamine-based novel PET sensors in selective recognition of dicarboxylic acids

The triphenylamine-based chemosensors 1 and 2 have been designed and synthesized, for the first time, for the selective recognition of dicarboxylic acids. Carboxylic acid binding takes place through charge neutral pyridyl amide receptor sites with concomitant quenching of fluorescence of the triphenylamine moiety. The bindings were examined using ¹H NMR, fluorescence and UV-vis spectroscopic methods. The receptor 1 was found to be selective for glutaric and adipic acids and the macrocycle 2 was specific for 2,2-dimethylmalonic acid.     

Epoxy acids of the seed oil ofArtemisia absinthium

Summary 1. The seed oil of the Central Asian common wormwood has yielded 1.48% of cis-12,13-epoxyoctadec-cis-9-enoic acid, 5.94% of cis-9,10-epoxyoctadec-cis-12-enoic acid, and traces of 9,10-epoxyoctadecanoic acid, and their structures have been confirmed.2. It is proposed to used the neutralization number of fatty acids to determine the amounts of epoxy acids in their combinations with -hydroxydienic acids.3. The possibility has been shown of determining the amount of ratio of the isomeric epoxy acids using oxidative degradation of the total oxy acids.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 705–710, November–December, 1976.     

Acrylic acid polymerization kinetics

The kinetics of the isothermal polymerization of acrylic acid were determined utilizing ¹H-NMR spectroscopy. The polymerization rate was observed to depend approximately on the $ \frac{3}{2} $ power of monomer and the $ \frac{1}{2} $ power of sodium persulfate concentration. This is consistent with a model in which the rate of initiation is itself dependent on the monomer concentration. The polymerization rate was also observed to have a strong dependence on percent neutralization, decreasing with increasing level of neutralization up to 75 to 100% neutralization, and then increasing again. The activation energy for the rate of polymerization was between 9 and 13 kcal/mol except for 100% neutralized acrylic acid, which had an activation energy of 18 kcal/mol. These data suggest that a transition in mechanism occurred at 100% neutralization. Increasing the ionic strength by the addition of sodium chloride also increased the rate. The dependence of the molecular weight on the above variables was also quantified for use in the model. It decreased with increasing conversion, decreasing ionic strength and increasing initiator. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2029–2047, 1997     

Preparation of α,α-difluoroalkanesulfonic acids

Chlorodifluoromethanesulfonic acid (1) was prepared using a new procedure starting from perchloromercaptan, which is readily obtained from chlorination of CS₂. Modified Swarts reaction transformed N,N-diethyl trichloromethanesulfenamide into N,N-diethyl chlorodifluoromethanesulfenamide, and the latter species was further oxidized and hydrolyzed into chlorodifluoromethanesulfonic acid. The preparations of other two new α,α-difluoroalkanesulfonic acids, phenyl difluoromethanesulfonic acid (2) and 2-phenyl-1,1,2,2,-tetrafluoroethanesulfonic acid (3), are also disclosed. The acids 2 and 3 are stable in the forms of sodium (lithium) salts or in aqueous solutions; however, the pure forms of 2 and 3 can readily undergo defluorinations. 1-3 and their salts have potential applications as superacid catalysts and lithium battery electrolytes.     

Katalytische Wirkung von Azobenzol in sauren Medien auf die Wasserstoffentwicklung an der tropfenden Quecksilberelektrode

Catalytic effect of azobenzene in acid media (pH<4.0) on hydrogen evolution at theDME is studied with special reference to its dependence on the H⁺ ion concentration in the solution. Comparison is made between the effect of strong and weak monobasic acids and polybasic acids on the catalytic current. The effect of surface active substances and the substituents is described.

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