ISSN:0021-2148    

DOI:10.1002/ijch.197100045

出版商:WILEY‐VCH Verlag    

年代:1971

数据来源: WILEY

摘要:

AbstractRate constants (k2Wor k2A) for proton exchange between a phenol, its conjugate base, and a water ort‐butyl alcohol molecule have been measured in at‐butyl alcohol‐water mixture by nuclear magnetic resonance. Since k2Wand k2Aare both high (k2W>108sec−1M−1), the ratio k2W/k2Ameasures the selective solvation of the O−‐site (of the phenoxide ions) by water andt‐butyl alcohol. In 11.47 mole %t‐butyl alcohol — 88.53 mole % water, k2W/k2Ais found to be 14 ± 3 when the ionic reactant isortho‐bromophenoxide ion, and 32 ± 8 when it ismeta‐nitrophenoxide ion. The results suggest that substituents have a marked effect on the selective

ISSN:0021-2148    

DOI:10.1002/ijch.197100046

出版商:WILEY‐VCH Verlag    

年代:1971

数据来源: WILEY

摘要:

AbstractThe use of nuclear magnetic resonance spectroscopy for the study of the properties and structure of solvation shell complexes is discussed through the example of Co2+ions in methanol. New proton relaxation and shift measurements in solutions of Mn(ClO4)2and Cr(ClO4)3in anhydrous methanol are described and analyzed. The results yield kinetic and magnetic parameters for the [Mn(CH3OH)6]2+and [Cr(CH3OH)6]3+solvates. The dominant kinetic process for Mn2+involves exchange of whole molecules in and out of the solvation shell, while for Cr3+only the protolysis reaction of the hydroxyl protons affects the NMR resonance. Both ions have relatively long electron spin relaxation times and it is therefore not possible to observe their solvation shell directly. Preliminary results on Cu2+solvates are also discussed.

ISSN:0021-2148    

DOI:10.1002/ijch.197100047

出版商:WILEY‐VCH Verlag    

年代:1971

数据来源: WILEY

摘要:

AbstractThe salt effects in many reactions between anions are compared with the predictions of the Brønsted‐Debye theory, and with the assumption of formation of reactive ion pairs; both approaches appear to be inadequate. Clear evidence is available (change of activation energy, effect of organic ions, effect of complex ions) that at least part of the salt effects is non‐electrostatic in nature, so that the introduction of appropriate structural parameters in a general electrostatic treatment is required for their explanation. The Debye‐Hückel theory cannot be used as a frame for the introduction of such parameters, but a more flexible and self‐consistent theory is required. Evidence is presented that the Mayer theory can interpret thermodynamic properties even in cases where the Debye‐Hückel theory fails, and a method is suggested whereby the Mayer theory is used to interpret the salt effect and to give a structural meaning to the empirical parameters which must b

ISSN:0021-2148    

DOI:10.1002/ijch.197100048

出版商:WILEY‐VCH Verlag    

年代:1971

数据来源: WILEY

摘要:

AbstractThe kinetics and mechanism of the catalytic decomposition of H2O2by Fe3+ion, haemin and catalase are discussed. A general mechanism is set up. The kinetic features of the three catalytic systems are discussed in terms of this mechanism.

ISSN:0021-2148    

DOI:10.1002/ijch.197100049

出版商:WILEY‐VCH Verlag    

年代:1971

数据来源: WILEY

摘要:

AbstractThe model of Bascombe and Bell for the indicator acidity of concentrated acid solutions is applied to the analysis of acid catalyzed reactions. A number of well studied reactions are shown to obey the relationship:where Cwis the molar concentration of water not bound to proton (or to hydroxyl OH−). Values of Cwfor use in the above correlation are calculated, assuming the existence of the proton in the form suggested by Eigen, H3O(H2O)3+. The volume fractions of nonbound water are also calculated, this quantity giving even better correlation in some cases. Values of n are obtained which agree, after subtraction of water molecules given up by the proton, with the number of water molecules which can be expected to participate in the formation of the transition state of these reaction

ISSN:0021-2148    

DOI:10.1002/ijch.197100050

出版商:WILEY‐VCH Verlag    

年代:1971

数据来源: WILEY

摘要:

AbstractThe experimental techniques for the study of the extremely fast reactions of hydrogen‐bond formation are reviewed. Direct high field dielectric and acoustic techniques as well as indirect NMR and dielectric methods are available; examples of their application to specific problems are given.Bond formation and bond transfer reactions must be distinguished. The mechanism of bond transfer can be of different types, similar to the associative and dissociative types of substitution mechanisms that were formulated for other classes of reaction

ISSN:0021-2148    

DOI:10.1002/ijch.197100051

出版商:WILEY‐VCH Verlag    

年代:1971

数据来源: WILEY

摘要:

AbstractInstances of temperature‐dependent apparent energies of activation EA, observed for hydrolysis reactions, are briefly reviewed, as are recent calculations according to which the presence of a reactant in two forms which are in mobile equilibrium may lead to a temperature‐dependent EA. These calculations are extended to a consideration of the temperature‐dependence of the specific heat of activation, and to the possibility of more than two forms being in equilibrium. It is shown in some detail how the equilibrium between broken and intact hydrogen bonds in water may be responsible for observed ef

ISSN:0021-2148    

DOI:10.1002/ijch.197100052

出版商:WILEY‐VCH Verlag    

年代:1971

数据来源: WILEY

摘要:

AbstractThe commonly held Gross‐Butler theory of isotope effects in mixed H2O‐D2O solvents is reexamined. Special attention is given to the conventional separation of the free energy changes responsible for the isotope effect into contributions from “transfer” and “exchange”. The internal inconsistency of the theory is pointed out and its empirical utility is

ISSN:0021-2148    

DOI:10.1002/ijch.197100053

出版商:WILEY‐VCH Verlag    

年代:1971

数据来源: WILEY

摘要:

AbstractMeasurement of rates of abstraction of H atoms by aqueous OH radicals from specific sites in aliphatic amides by the technique of pulse radiolysis‐kinetic spectroscopy establishes that in this reaction, in which gross rates of reaction fall short of the diffusion‐controlled limit by no more than a factor of 102, there is a systematic variation of reactivity with structure. This variation parallels dependence of reactivity upon structure observed in the reactions of several other free radicals in the gas ph

ISSN:0021-2148    

DOI:10.1002/ijch.197100054

出版商:WILEY‐VCH Verlag    

年代:1971

数据来源: WILEY