酸碱软硬度的水合热标度法

本文用水合热法对酸碱的软硬度进行了新的标度,提出了f_h=△H/X+14.29X-11.43作为软硬酸的标度参数;φh=△H/Z+26.25X-74.55作为软硬碱的标度参数。对酸碱得到了与Pearson分类较一致的结果。     

酸碱软硬度的键参数标度

本文以有效核电荷Ｚ＊、半径ｒ和电负性Ｘ为参数，提出一种新的酸碱软硬度的键参数标度法，以ｆ＝Ｚ＊／ｒ２－２０Ｘ＋２４作为软硬酸的标度参数，不仅可以标度各种简单离子，对原子也同样适用；以＝Ｚ＊／ｒ２＋５Ｘ－１５作为软硬碱的标度参数，并推知对于碱的软硬度大致可用电负性来衡量。该标度法可定量比较酸碱的软硬度，结果与Ｐｅａｒｓｏｎ分类基本一致     

一些非共轭有机化合物基团应用HSAB原则的键参数标度

关于软硬酸碱原则(HSAB)在有机化学上的应用,已有不少论述。但对其定量标度尚很少取得进展。徐辉碧和龙耀庭扩展了刘祁涛提出的用电负性(x)和离子势(z/r)两个键参数对HSAB原则进行定量标度的概念,尝试用诱导效应指数代替电负性以及应用电荷与非球形离子热化学半径比,作为键参数,计算了十七种复杂无机离子的酸碱软硬度值。     

软硬酸碱理论的新进展

本文综合介绍了国内外几种软硬酸碱理论,着重讨论了皮尔逊(Pearson)提出的最新软硬酸碱理论,并将几种理论进行了比较。新均软硬酸碱理论的优点在于将酸碱的软硬特性和电子的逃逸倾向(电子化学势)和转移的电子数联系起来。软硬标度的计算公式只用了物质的两个重要原子参数(电离势,和电子亲和势 E_A)它既可计算酸的硬度也可以计算碱的硬度,并可说明软硬酸碱原则。     

溶剂的Lewis碱性标度研究进展

总结了溶剂的Lewis碱性标度研究的进展。介绍了各种标度的基本原理,特别着重介绍了80年代以来的新发展,其中包括量热标度的新进展;建立在单一参考酸(溶质)的紫外-可见光谱、红外、拉曼光谱和核磁共振谱等分子性质基础上的非量热标度;考虑到软硬酸碱原理的双重标度;考虑到电价作用和共价作用两者的多参数标度。比较和讨论了各种标度的优点、不足、适用范围和相互联系。提出了在目前研究水平上应用溶剂Lewis碱性标度的建议。     

酸碱的软硬度的势标度及其相亲强度和络合物的稳定度

广义的酸碱包括的物质种类极为广泛,绝大多数化合物皆可看作是酸碱的加合物。所有的化学反应,除氧化还原反应而外,皆属酸碱反应。因此,酸碱的软硬概念和“硬亲硬、软亲软”原理有广泛的联系。软硬酸碱原理的提出完全是经验的总结。后来有人应用前沿分子轨道微扰理论予以说明,从而使之具有理论的意义。但至今还没有一个定量标度可以把酸碱的软硬性和它们的反应性或其它性质联系起来。实际上,已有多人根据酸碱的若干基本性质,如电负性、电离     

软硬酸碱理论的发展和应用

从软硬酸碱理论的起源出发,简要介绍软硬酸碱理论的建立背景、发展过程,并对其可能的应用范围做了讨论.最后结合人们对于软硬酸碱理论的认识和应用现状,做出总结和评价.     

软硬酸碱规则与体内微量元素

阐述了ＳＨＡＢ规则,分类,酸碱软硬度的定量标度和理论解释。根据ＳＨＡＢ规则把体内微量元素分为Ｌｅｗｉｓ硬酸,软酸与交界酸和硬碱,软碱与交界碱,体内不同体液和器官含有丰富的软硬配体,与各类软硬酸（金属离子）结合成不同稳定性的配合物,发挥其生物活性作用。     

二价金属离子萃取速率常数与软硬酸碱规则

用上升液滴法测定了２－乙基己基膦酸单（２－乙基己基）酯－正辛烷从硝酸介质中萃取镁、钙、锌、镍、铜和铅等二价金属离子的正向初始速率，建立了速率方程，计算出正向萃取反应的速率常数、活化能及活化熵，首次将软硬酸碱规则与金属溶萃取速率常数关联。结果表明，在萃取机理相同时，萃取速率常数的大小与金属离子的软硬酸碱标度一致，即萃取过程中，作为酸的被萃取金属离子，其硬度越大，萃取速率常数亦越大，萃取反应的活化能…     

金属萃取平衡与软-硬酸碱规则

软硬酸碱规则从宏观角度描述化合物的形成及性质,在配合物稳定性的判断方面有广泛应用.前文^[1]报道了萃取速率常数与金属离子的软硬酸碱强度的关系,本文研究了萃取平衡常数与金属离子的软硬酸碱强度的关系.     

高效离子交换色谱法分离和测定氯溴碘

用国产高效离子交换色谱仪及国产阴离子交换树脂研究了分离Cl^-、Br^-、Ⅰ^-的条件,以硝酸钠为洗脱液,在三十五分钟内完全分离了上述三种离子。进行了一些样品的定量测定。用无换向阀的予柱富集测定了去离子水中ppb级的Cl^-。从软硬酸碱理论的观点讨论了Cl^-、Br^-.Ⅰ^-的色谱行为,得出了用结构参数及实验条件估算分配系数的经验式:1gD=0.24φg[B]-1g[B]+0.49φ+0.61。     

镍电极在硼砂-硼酸缓冲溶液中的钝化和点蚀

近年来交流阻抗技术用于研究局部腐蚀,尤其在点蚀方面,引起了很大兴趣。Mansfeld等人和Oltra等人都提出了电极在点蚀时的等效电路.有关镍电极在Cl~-存在时的点蚀研究有过许多报导,但是至今尚未见到用交流阻抗技术研究Ni电极的点蚀.本文用交流阻抗技术对Ni电极在Na_2SO_4硼砂-硼酸缓冲溶液(pH8.4)中的钝化行为和Cl~-存在时的点蚀行为进行了研究,探讨了钝化和点蚀的规律和机理。     

Elucidating the hard/soft acid/base principle: a perspective based on half-reactions

A comprehensive analysis is presented for the acid-base double-exchange reaction as well as the associated acid-displacement and base-displacement "half-reactions" with the goal of elucidating the meaning of the hard/soft acid/base (HSAB) principle and the conditions for its validity. When electron-transfer effects are important and other effects are negligible, the HSAB principle is driven by the surpassing stability of the soft acid/soft base product. When electrostatic effects dominate the reactivity, the HSAB principle is driven by the surpassing stability of the hard acid/hard base product. Because electron-transfer effects favor soft/soft interactions, while electrostatic effects favor hard/hard interactions, acid-base exchange reactions may be used to determine whether a reagent's reactivity is dominated by electron-transfer or by electrostatic effects. Because electron-transfer and electrostatic considerations separately favor the HSAB principle whenever the electronic chemical potentials of the acids and bases involved in the reaction are similar, our analysis provides strong support for the HSAB principle. The electronic chemical potential measures the intrinsic strength of acids and bases.     

A perimidine-derived non-Kekulé triplet diradical

6,9-Di(tert-butyl)-1-methyltetrazolo[1,5-a]perimidine (1) has been synthesized from naphthalene in seven steps. The EPR spectra, recorded after irradiation of 1 in a butyronitrile matrix at 77 K (lambda = 351 nm) and in Ar and Xe matrixes at 4.6 K (lambda > or = 345 nm), showed a six-line, high-field signal (Delta m(S) = +/- 1), centered at 3350 G in butyronitrile, along with a half-field signal (Delta m(S) = +/- 2), which is characteristic for triplets. Simulation of the observed EPR spectra gave values for the zero-field splitting parameters of |D/hc|/cm(-1) = 0.0105, |E/hc|/cm(-1) = 0.0014 in butyronitrile and |D/hc|/cm(-1) = 0.0107, |E/hc|/cm(-1) = 0.0016 in Ar. These EPR parameters are consistent with the diradical 5,8-di(tert-butyl)-2-(N-methylimino)perimidine-1,3-diyl ((3)2) as source of the EPR spectra. Linearity of the Curie-Weiss plot and UB3LYP and (14/14)CASPT2 calculations of the singlet-triplet energy difference (DeltaE(ST) approximately 8-10 kcal/mol) indicate that the triplet is the ground state of 2, as predicted for such a nondisjoint diradical.     

THE EFFECT OF ACIDS ON THE INFRARED SPECTRA OF SCHIFF BASES—II. IMINES CONTAINING THE C=C-C=N AND C=C-C=C-C=N UNITS

Abstract— The Fourier-transform infrared spectra of chloroform-d solutions of conjugated imines CH₃CH=CHCH=NCH(CH₃)₂ and CH₃CH₂CH=CHCH=CHCH=NCH(CH₃)₂ and the related protonated species with HCl, HBr, HI, trichloro, dichloro, monobromo and monochloroacetic acids or propionic acid are presented. The effects of conjugation and protonation are examined. The results show that conjugation slightly increases the basicity of the Schiff bases. HCl, HBr and HI protonate the Schiff bases completely. The carboxylic acids protonate partially depending on their p K _a, values. When the Schiff base contains two (or more) C=C bonds conjugated with C=N, the main C=C stretching band undergoes a strong intensification showing that sizeable dipole moment variations occur along the conjugated chain.     

气相色谱法测定甲苯和正癸烷在聚苯乙烯溶液中无限稀时的活度系数

用气相色谱法测定了130°—200℃之间甲苯和正癸烷在四个分子量不同的聚苯乙烯样品的溶液中无限稀时的活度系数和Flory-Huggins相互作用参量。对于φCH_3-PSt系统,得到: In Υ(O)= -1.0505lnZ+1.1031,(130—201℃)对于nC_10~0-PSt系统,得到: ln Υ(O)= -0.9761lnZ+1.9631,(130—201℃)表明两系统均接近于无热溶液。对于170—201℃的φCH_3-PSt系统,得到: 1+X=4.857Z~(-1)+0.7560据此对气相色谱法测定高聚物分子量的可能性进行了讨论。     

An elementary derivation of the hard/soft-acid/base principle

The hard/soft-acid/base (HSAB) principle indicates that hard acids prefer binding to hard bases (often forming bonds with substantial ionic character) while soft acids prefer binding to soft bases (often forming bonds with substantial covalent character). Though the HSAB principle is a foundational concept of the modern theory of acids and bases, the theoretical underpinnings of the HSAB principle remain murky. This paper examines the exchange reaction, wherein two molecules, one the product of reacting a hard acid and a soft base and the other the product of reacting a soft acid with a hard base, exchange substituents to form the preferred hard-hard and soft-soft product. A simple derivation shows that this reaction is exothermic, proving the validity of the HSAB principle. The analysis leads to the simple and conceptually appealing conclusion that the HSAB principle is a driven by simple electron transfer effects.     

INVESTIGATION INTO THE SPECTROSCOPY AND PHOTOISOMERIZATION OF A SERIES OF POLY (ETHYLENE GLYCOL) PEPTIDE SCHIFF BASES OF 11-cis RETINAL

Abstract— The 11-cis and all-trans isomers of a series of poly(ethylene glycol)-oligopeptide - Schiff bases as models for rhodopsin were synthesized and studied. Absorption data for certain of the PEG-peptide Schiff bases demonstrated that no intramolecular hydrogen-bonding (or protonation) occurs between the Schiff base and an acidic amino acid residue, as was previously thought. Photoisomerization of the 11-cis protonated and unprotonated Schiff bases were examined using both steady state and laser flash techniques. Also with 355 nm excitation (and additionally 532 nm in one case), an approximate 40% increase in quantum yield of isomerization (φ) occurred for all protonated PEG-peptide Schiff bases compared to the H⁺-n-butylamine counterparts (in methanol). In one case, a > 100% increase in φ was found in dichloromethane. These data show that PEG-oligopeptide Schiff bases are still further improved models for rhodopsin compared to their n-butylamine analogs.     

光透薄层光谱电化学法研究紫脲酸铵电还原过程

采用金网橱光透薄层电解池, 配合紫外可见光谱技术现场监测了有机染料紫脲酸铵的电还原过程。用光透薄层光谱电化学方法测定了紫脲酸铵在pH5.0醋酸盐缓冲溶液中的式电极电位和电子转移数。薄层循环伏安法和薄层光谱电化学法研究表明, 紫脲酸铵在金网栅电极上的还原为双电子转移不可逆过程, pH<8时, 还原产物双巴比士亚胺进一步分解为尿咪和巴比士酸。用双电位跃-计时吸收谱法研究了双巴比士亚胺在不同pH缓冲溶液中的分解动力学过程, 测定了拟-级反应动力学常数。