A new interpretation of the kinetics of the reaction between carboxylic acids and diazodiphenylmethane in toluene.

Chapman, N. B.; Ehsan, A.; Shorter, J.; Toyne, Kenneth J.

doi:10.1016/s0040-4039(01)98888-4

Cited by 3 publications

(3 citation statements)

References 17 publications

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“…They found that this ion pair formed finally the relevant ester and nitrogen and that its second‐order rate constant, k varied with acid concentration, c as

k \sqrt{c} = k_{0} + k_{1} \sqrt{c} + k_{2} normalc

where k 0 represented the spontaneous rate constant, and k 1 and k 2 referred to the catalytic constants for the monomer acid and the reactive dimer acid, respectively. They interpreted the result in terms of the reversible formation of an intermediate complex, which broke down into the products spontaneously as well as catalytically by another acid molecule (monomer and/or multimer) …”

Section: Acid–base Catalysis and Acid–base Strengths In Apolar Aprotimentioning

confidence: 99%

Proton transfer rate‐equilibria in apolar aprotic solvents: a historical perspective

Gupta

2016

J of Physical Organic Chem

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Low dielectric constant apolar aprotic solvents, although employed on a limited scale for studying proton transfer reactions as compared with commonly used polar protic or dipolar aprotic ones, offer some particular advantages, namely, specific solute-solvent interactions are virtually eliminated and proton transfer occurs directly in an apolar aprotic solvent. An intriguing feature of these reactions is their general acid-catalyzed/base-catalyzed kinetics with a time scale over microseconds to minutes. In fact, the true or intrinsic relative strengths of acids/bases when measured in such solvents come to the fore much more clearly than those obtained in other classes of solvents. Recently, a review documenting the post-1980 developments relating to proton transfer reactions in apolar aprotic solvents has been published. The present article is a commentary of the pre-1980 developments in this area since the 1920s Brønsted-Lowry's "proton cult" of acid-base theory. dia since 1976 till 2013 when he superannuated as the Dean, Faculty of Science of the University. Currently, he is an Emeritus Professor at Banaras Hindu University, Varanasi. His research interests are origin, non-faradaic chemical effects and applications of contact glow discharge electrolysis, and kinetics and mechanism of proton transfer processes in apolar aprotic media and quantitative structure-reactivity relationships. Further research activities concern transmission modes of anomalous substituent effects on 13 C chemical shifts in aromatic molecules and ferrospinel catalysts.

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“…They found that this ion pair formed finally the relevant ester and nitrogen and that its second‐order rate constant, k varied with acid concentration, c as

k \sqrt{c} = k_{0} + k_{1} \sqrt{c} + k_{2} normalc

Section: Acid–base Catalysis and Acid–base Strengths In Apolar Aprotimentioning

confidence: 99%

Proton transfer rate‐equilibria in apolar aprotic solvents: a historical perspective

Gupta

2016

J of Physical Organic Chem

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“…It is hard to imagine how an acid dimer could possess more reactivity than the monomer, "tied" as it is in a cyclic structure. Chapman, Ehsan, Shorter, and Toyne (33) have accordingly put forward an alternative explanation. They regard the acid monomer as the more reactive species.…”

Section: Acid Associationmentioning

confidence: 99%

Probing chemical reactivity with the diphenyldiazomethane reaction

Dack¹

1972

J. Chem. Educ.

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Probing Chemical Reactivity with the Diphenyldiazomethane ReactionRates of organic reactions can be altered in a multitude of ways. The effects which cause rate changes have consequently lent themselves to widespread investigation, not only from an academic viewpoint, but also as an aid to industry and to medicine. An accelerated reaction will yield its products in less time, thereby reducing operating costs and freeing expensive equipment for other work. Alternatively, methods for stabilizing drugs are of constant concern to medicinal chemists, since compounds which undergo decomposition or unwanted side reactions are of little use in therapy.The physical-organic chemist, therefore, requires a suitable reaction system on which to study the effects of temperature, pressure, solvent, and other variables. One such system is the reaction between diphenyldiazomethane (DDM) and carboxylic acids-the "DDM reaction." As DDM becomes consumed in the reaction, its deep red color gradually disappears, and the resulting decrease in optical density is easily monitored speetrophotometrically. Thus, once the acid and DDM have been mixed in solution, the reaction can be followed without recourse to the sampling and subsequent product analyses of other kinetic techniques. Substituents introduced into the carboxylic acid often produce considerable variations in rate; a change of solvent may also have a similar effect. In addition, it is possible to work with very small amounts of materials. However, the fact that an acceptable mechanism exists for the DDM reaction in hydroxylic solvents probably overshadows all these advantages. It stands to reason that measurements made on a reaction without a full knowledge of that reaction run the risk of misinterpretation. Evaluation of kinetic data is difficult enough even in the absence of this extra hazard! The Diphenyldiazomethane Reaction A systematic investigation of the esterification of carboxylic acids by DDM was started by J. D. Roberts and his co-workers in 1949 (1-5). They followed the reaction of a number of acids with DDM in ethanol at 30°C and found that strong acids catalyzed the reaction between DDM and the solvent to give ethyl diphenylmethy] ether. Weak acids, however, gave the diphenylmethyl ester of the acid as the major product, along with the product of the acid-catalyzed reaction with the solvent. The reaction was found to be firstorder in both acid and DDM (3). As a result, it can be conveniently conducted under pseudo first-order condi-

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“…The vast majority of pre‐1980 progress since the 1920s Brønsted–Lowry proton cult in studies on the thermodynamic aspects of proton transfer between various carboxylic acids, phenols and fluoro‐alcohols/nitro‐alcohols, and organic bases of different classes in different apolar aprotic solvents by Brønsted, Hall, La Mer and Downes, Griffith, Hantzsch, Weissberger and Fasold, Barrow et al ., Cook, Gramstad, Zeegers‐Huyskens, Denisov et al ., Bruckenstein et al ., De Tar et al ., Bell et al ., Anderson, Pearson et al ., Bayles et al ., Popovych, Davis et al ., Jasinski et al ., Steigman et al ., Vinogradov et al ., Parbhoo et al ., Walker et al ., Sobczyk et al ., and Simmons et al . and their kinetic and catalytic aspects by Brønsted et al ., Hartman et al ., Bell et al ., Crooks et al ., Simmons et al ., Robinson et al ., Caldin et al ., Ivin et al ., Burfoot et al ., Palit et al ., and Chapman using infrared (IR), ultraviolet (UV)–visible spectrophotometry of the ion‐pair product and microwave and laser pulse temperature jump as well as stopped flow concentration‐jump techniques has been reviewed by Hall, La Mer and Downes, Davis, Crooks and Robinson, Robinson, Simmons, and Zeegers‐Huyskens and Huyskens…”

Section: Introductionmentioning

confidence: 99%

Proton transfer reactions in apolar aprotic solvents

Gupta

2015

J of Physical Organic Chem

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Proton transfer reactions are advantageously investigated in low‐dielectric‐constant apolar aprotic solvents where specific solute–solvent interactions are greatly minimized, if not eliminated, and proton transfer occurs directly. An intriguing feature of these reactions is their general acid/base‐catalyzed kinetics with a timescale over microseconds to minutes. Proton‐coupled electron transfer (PCET), a great promise in the development of renewable energy sources, is an emerging application of the reactions. This article is an updated review of the post‐1980 developments in understanding the mechanism of proton transfer reactions, quantitative structure–reactivity relationships, acid/base‐catalyzed molecular rearrangements, reverse trends between acidity parameters and 13C δco (a measure of electron population at the carboxyl carbon) in aromatic carboxylic acids, coupling of proton transfer with electron transfer, and PCET reactions in suitably designed model systems in apolar aprotic solvents for renewable energy devices. Copyright © 2015 John Wiley & Sons, Ltd.

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A new interpretation of the kinetics of the reaction between carboxylic acids and diazodiphenylmethane in toluene.

Cited by 3 publications

References 17 publications

Proton transfer rate‐equilibria in apolar aprotic solvents: a historical perspective

Proton transfer rate‐equilibria in apolar aprotic solvents: a historical perspective

Probing chemical reactivity with the diphenyldiazomethane reaction

Proton transfer reactions in apolar aprotic solvents

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