Specific Salt Effects Research Articles

A depressing specific salt effect on the hydrolysis of an iminium ion

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTA depressing specific salt effect on the hydrolysis of an iminium ionJohn L. Hogg and William P. JencksCite this: J. Am. Chem. Soc. 1976, 98, 18, 5643–5645Publication Date (Print):September 1, 1976Publication History Published online1 May 2002Published inissue 1 September 1976https://doi.org/10.1021/ja00434a039RIGHTS & PERMISSIONSArticle Views134Altmetric-Citations6LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (339 KB) Get e-Alerts Get e-Alerts

Kinetics of reaction of p-nitrophenyl methyl carbonate with nucleophiles in aqueous solution, and the relative ease of acetyl and methoxycarbonyl transfer reactions

The rate constants for reaction of eight nitrogen and four oxygen bases with p-nitrophenyl methyl carbonate in water at 25 °C have been measured, and are closely similar to published values for p-nitrophenyl acetate. General acid catalysis is not observed in the methoxyaminolysis of the carbonate, unlike the acetate. Specific salt effects are shown to preclude conclusions regarding the extent of general base catalysis in these reactions. The rate constant for reactions of propylamine with the 1-methoxycarbonyl-4-methylpyridinium ion has also been measured, and is compared with the published value for the 1-acetyl compound.

Salt effects in the glutathione-facilitated reactivation of reduced bovine pancreatic ribonuclease.

The rate of regeneration of reduced RNase by glutathione was examined in the presence of several added substances: substrate, phospholipid, other proteins, bacterial ribosomes, and neutral salts. Of these, only neutral salts showed substantial effects. K2HOP4 and (NH4)2SO4 strongly accelerated regeneration, the alkali chlorides showed moderate acceleration or inhibition, while LiBr and KSCN strongly inhibited. The t1/2 for regeneration in 1 M Pi is 4 min compared to 75 min in the absence of Pi; in 0.5 M KSCN t1/2 greater than 100 min. The pattern of specific salt effects is similar to a Hofmeister series. There is a strong parallel between the pattern of specific salt effects on the kinetics of RNase regeneration and the pattern of effects of the same salts on the equilibrium stability of biopolymers. This suggests that the role of salts in the regeneration is to stabilize or destabilize rate-limiting folding intermediates. Pi-accelerated glutathione regenerations showed a broad temperature optimum from 30-37 degrees. In strong contrast with the virtual concentration independence of the Pi-free controls, with Pi = 1 M, both rates and yields of RNase activity were decreased markedly at [RNase] greater than 2 x 10(-6) M. Phosphate and pyrophosphate showed additive, and in some cases, synergistic accelerations. These results suggest that specific ion binding occurs in addition to general solvent effects.

Influence of potassium and calcium chlorides on the anticholine sterase activity of esters of diphenylphosphinic and diphenylthiophosphinic acids

1. The influence of KCl and CaCl2 on the inhibition of the catalytic activity of butyrylcholinesterase (BuCE) and acetylcholinesterase (ACE) by cationic organophosphorus inhibitors with combined action and with a reversible type of inhibition was investigated at 25‡, pH 7.5, and ionic strength (Μ) 0.0044, 0.11, and 0.55. Increasing Μ reduces irreversible and reversible inhibition. 2. In the case of the same increase in Μ, the influence of KCl on the values of the inhibitor constants, as a rule, was substantially greater than the influence of CaCl2; ACE proved to be more sensitive to a change in Μ than BuCE. The presence of specific salt effects in the reactions of cholinesterases was demonstrated.

Water structure and unusual medium effects in the reaction between [Co(NH 3) 5B] 2+ and Fe 2+

The influence of electrolytes, of various alcohols at low concentrations, and of temperature on the rate of the electron transfer between [Co(NH 3) 5Br] 2+ and Fe 2+ has been investigated. Specific salt effects are reported. Systems of different electrolyte composition have significantly different energies of activation. Reaction mixtures containing HClO4 as the supporting electrolyte have positive Δ C # p . The rate constant as a function of alcohol concentration passes through a minimum at low temperatures. An isokinetic relationship is found to hold with d ΔH #/d ΔS # = 298°K. The observed effects are tentatively ascribed to the influence of water structure.

Etude cinetique de la catalyse par LiClO 4 de la reaction d'esterification des olefines

LiClO 4 catalyses the addition of CHCl 2CO 2H to olefins (cyclopentene cycloheptene and trans-cyclo-octene). Specific salt effects are discussed in terms of general acid catalysis. This mechanism is supported by the linear relation: log k ex = − αH o + β. Solvent isotope effects show a slow proton transfer. Eyring parameters are determined; ΔS* < 0. These experiments are consistent with a mechanism involving carbocation formation as the slow step.

Acid decomposition of decavanadate: specific salt effects

The reaction of decavanadate(V), V10O286–, and also the reduced decavanadate VIV7VV3O2813–, with acid in the presence of a number of supporting electrolytes has been studied. Large cations such as tetra-alkylammonium ions and trialkylsulphonium ions markedly decrease the rate of reaction. This is shown to be due to the formation of stable ion pairs with decavanadate which do not react with acid. The effect is greater the larger the size of the onium ion. Such ion pairs do not form with the alkali-metal cations.

Structure of DNA in denaturing solvents: I. Bacteriophage PM2 DNA in aqueous sodium perchlorate

The sedimentation velocity behavior of both closed (I) and nicked (II) circular bacteriophage PM2 DNA's has been determined in aqueous NaClO 4 solutions ranging from 0.98 to 7.2 m. The addition of the salt results in a progressive, non-cooperative unwinding of the DNA duplex to the extent of 3.9% at 7.2 m-NaClO 4, as determined by comparison with the sedimentation velocity/dye titration results of Upholt, Gray & Vinograd (1971), The salt-induced unwinding is complemented and extended by the intercalation of ethidium bromide, and the shape of the sedimentation velocity/dye titration curve in 0.98 m-NaClO 4 is similar to that in 2.85 m-CsCl ( Upholt et al., 1971) . The sedimentation coefficient ratio S I S II has the same dependence upon NaClO 4 concentration at 5 °C and at 20 °C, except for an effective translation to 0.8 m higher salt concentrations at the lower temperature. This shift is consistent with the known effects of temperature upon the duplex rotation angle ( Wang, 1969). The unwinding of the DNA duplex in the presence of increasing NaClO 4 concentrations is to be contrasted with the much smaller overwinding which occurs upon the addition of NaCl or CsCl at 20 °C ( Wang, 1969). The NaClO 4-induced unwinding takes place at temperatures well below the onset of the melting transition, and the specific salt effect does not appear to have a large temperature coefficient. The results indicate that substantial angular alteration of the duplex may be induced by a change in solution environment in the absence of transition to the coiled form of DNA.

Aziridines related to some β-adrenergic blocking agents. Kinetics of formation and reaction, and some unusual salt effects

The cyclisation rates of some β-chloroethylamines to the aziridine have been measured. Rates and activation parameters are used to demonstrate mechanistic differences between those cyclisations that can, and those that cannot, obtain further assistance from benzylic or neighbouring aryl participation. The reactions of the aziridines with water and thiosulphate ion are studied. While primary products are obtained from one aziridine and secondary products from another, this does not allow a reliable distinction to be made between SN2 and SN1 pathways, to which the activation parameters provide a better guide. Unexpectedly large and specific salt effects are found for certain of the aziridine formation and solvolysis reactions. These enable conclusions to be drawn concerning all four transition states, for which tentative activity coefficients are derived. This analysis is incorporated in a scheme that consistently explains rates, salt effects, and activation parameters.

Specific salt effects upon the rates of SN1 solvolyses

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSpecific salt effects upon the rates of SN1 solvolysesClifford A. Bunton, T. W. Del Pesco, A. M. Dunlop, and Kui-Un YangCite this: J. Org. Chem. 1971, 36, 7, 887–897Publication Date (Print):April 1, 1971Publication History Published online1 May 2002Published inissue 1 April 1971https://doi.org/10.1021/jo00806a006RIGHTS & PERMISSIONSArticle Views196Altmetric-Citations15LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts

Hydrolysis of acetals and ortho esters. Specific salt effects associated with buffer experiments in mixed solvents

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTHydrolysis of acetals and ortho esters. Specific salt effects associated with buffer experiments in mixed solventsPentti Salomaa, Alpo Kankaanpera, and Markku LahtiCite this: J. Am. Chem. Soc. 1971, 93, 8, 2084–2085Publication Date (Print):April 1, 1971Publication History Published online1 May 2002Published inissue 1 April 1971https://doi.org/10.1021/ja00737a060RIGHTS & PERMISSIONSArticle Views74Altmetric-Citations8LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (289 KB) Get e-Alerts Get e-Alerts

Specific interactions of tetra-alkylammonium and alkali metal cations with anions in aqueous solutions

Precise measurements with electrochemical cells give specific interaction coefficients of tetra-alkylammonium ions with hydroxide and acetate ions in aqueous solution. Those with the hydroxide ion are useful in further analysis of specific kinetic salt effects of tetra-alkylammonium ions on the hydroxide-ion-catalized depolymerization of diacetone alcohol. Values of the specific interaction coefficients of tetra-alkylammonium cations with anions are tabulated and discussed in relation to corresponding values for alkali metal cations. A qualitative interpretation of trends in the coefficients is given in terms of ion-solvent competition, without invoking so-called “structural” explanations.

Model for the action of hemoglobin.

A model is developed for hemoglobin which depends on six Bohr groups per tetramer of hemoglobin. These six groups are assumed to be located in six regions between the four subunits of hemoglobin. When the Bohr groups are assumed to be perturbed in an asymmetrical manner on binding oxygen, these groups then generate the cooperative interactions of hemoglobin. This approach makes it possible to explain oxygen binding, the Bohr effect, specific salt effects, and aggregation effects in a unified manner.

A kinetic study of the reaction between octacyanomolybdate(V) and iodide ions

The rate of the reaction between octacyanomolybdate(V) and iodide has been measured by a microtitration method. The orders with respect to Mo(CN)83– and I– are a little larger than unity. Mo(CN)84– has a retarding effect. The reaction exhibits very specific salt effects in the order : (Et4N+ Li+ < (C2H4OH)4N+≃ Na+ < K+ < Mg++ < Ca++ < Ba++. The Olson–Simonson rule is approximately obeyed, but some specific effects due to anions are also present. A probable reaction mechanism is discussed.

σ-Bonded organotransition-metal ions. Part X. Kinetics and mechanism of the unimolecular hydrolysis of some pyridiomethyl metal carbonyl compounds in aqueous acid

The rate of decomposition of the 4-pyridiomethyl-pentacarbonylmanganese, -π-cyclopentadienyltricarbonyl-molybdenum and -π-cyclopentadienyltricarbonyltungsten ions in aqueous acidic solution is independent of acid and halide ion concentration except for a small, positive specific salt effect. The kinetics and products of these reactions show that they involve the unimolecular heterolysis of the saturated carbon to metal bond (SE1 at carbon, SN1 at metal). The decomposition of the 3-pyridiomethylpentacarbonyl-manganese and -π-cyclopentadienyl-tricarbonylmolybdenum ions is also independent of acid and halide ion concentration, and is believed to involve and initial unimolecular homolysis of the saturated carbon–metal bond. The 3- and 4-pyridiomethyl-π-cyclopentadienyldicarbonyliron ions are extremely stable, but, as their decomposition is influenced by the presence of oxygen, good kinetics were not observed.

Salt and activity effects on the precipitation of tetraphenylarsonium perchlorate

Alkali metal chlorides in the concentration range 0.006–4 M influence the solubility, crystal form and filterability of precipitated, tetraphenylarsonium perchlorate. Low salt concentrations increase, and high concentrations decrease the filterability and solubility. The mean activity coefficient of tetraphenylarsonium perchlorate is controlled by general and specific salt effects. Crystal nucleation is probably heterogeneous in low concentrations of salt and homogeneous in high concentrations.

Specific salt effects on the exchange reaction between 4,4′-dimethyldiphenylmethyl thiocyanate and ionic thiocyanate in acetone

Rates of exchange of 4,4′-dimethyldiphenylmethyl thiocyanate and MeSCN (Me = Li, Na, Bun4N) have been measured in acetone at 25°. With NaSCN the kinetics have also been investigated in the presence of a large amount of NaClO4, in all runs the total concentration of electrolytes, (NaSCN)+(NaClO4) being kept constant at 0·1 or 0·03M. With no salt other than MeSCN is the first-order rate coefficient, kobs, linearly dependent on the stoicheiometric concentration of the salt over a large interval (650 fold). With NaClO4, kobs is correlated with the stoicheiometric concentration of the nucleophile by a more complex kinetic expression. From the order of reactivity of different salts, LiSCN > NaSCN > Bun4NSCN, and the form of the kinetic equation a mechanism for the reaction is suggested which includes salt-assisted as well as solvent-assisted ionization paths. It is suggested that electrophilic assistance by salts leads to ion quadruplets which may return to covalent material without undergoing exchange or react with the nucleophilic salt to undergo exchange.

Aromatic nucleophilic substitution. Specific salt effects on rate constants with benzyltrimethylammonium methoxide in methanol

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAromatic nucleophilic substitution. Specific salt effects on rate constants with benzyltrimethylammonium methoxide in methanolWayne Hostetler and John D. ReinheimerCite this: J. Org. Chem. 1968, 33, 9, 3510–3513Publication Date (Print):September 1, 1968Publication History Published online1 May 2002Published inissue 1 September 1968https://doi.org/10.1021/jo01273a033RIGHTS & PERMISSIONSArticle Views64Altmetric-Citations3LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (496 KB) Get e-Alerts Get e-Alerts

Salt Effects in the Reaction of Peroxydisulfate with Thiosulfate

It can be deduced from a comparison of the salt effects in the reactions of persulfate with thiosulfate, of bromoacetate with thiosulfate, and of ethyl oxalate with hydroxide ions that the first of these reactions is subject to nonelectrostatic effects of great magnitude. The differences in the relative effects of the alkaline and of the alkaline-earth ions in the three reactions is attributed to the different hydration properties of the ion pairs in each case. In particular, it is concluded that the ion pairs with the hydroxide ion are formed without the intervention of water of hydration. The specific salt effects of various organic ions on the reaction between persulfate and thiosulfate are discussed on the basis of the mechanism of the nonelectrostatic effects.

335. Metal-ion catalysis and specific kinetic salt effects in the alkaline hydrolysis of half-esters of dicarboxylic acids

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