The Kinetics of the Decarboxylation of 2,4,6-Trihydroxybenzoic Acid in Perchloric Acid Solution

Schubert, Werner; Gardner, Jessica D.

doi:10.1021/ja01102a039

Cited by 19 publications

(8 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The kinetics of decarboxylation of 2 : 4 : 6-trihydroxybenzoic acid in aqueous solution was investigated by Brown, Elliot and Hammick 1 and by Schubert and Gardner. 2 The rate was found proportional to the concentration of the unionized acid HA, and at the same time, to the product of concentrations of H+ and A-:…”

mentioning

confidence: 87%

Kinetics and mechanism of the decarboxylation of salicylic acids

Willi¹

1959

Trans. Faraday Soc.

View full text Add to dashboard Cite

Decarboxylation rates of 4-Me, 4-OMe, 4-OH and 4-NH2 salicylic acids have been measured in aqueous solution at three different temperatures. The rates are proportional to the product, [anion] x [H+]. Bimolecular rate constants increase and activation energies decrease with increasing electron-donating power of the substituent . General acid-catalysis by anilinium and pyridinium ions has been detected. It is concluded that the mechanism is a bimolecular electrophilic substitution with a rate-determining proton transfer in the first step.

show abstract

mentioning

confidence: 87%

Kinetics and mechanism of the decarboxylation of salicylic acids

Willi¹

1959

Trans. Faraday Soc.

View full text Add to dashboard Cite

show abstract

“…The kinetics of decarboxylation of 2,4,6-trihydroxybenzoic acid at low concentrations in perchloric acid is studied by Schubert and Gardner (181), who follow the change in acid concentration from its absorbance in the range 250 to 275 µ. Gordon et al (82) analyze mixtures of aldehydes and ketones by carrying out a chromatographic separation, forming the 2,4-dinitrophenylhydrazones, and measuring absorbance at 356 µ. Daeniker (51) uses infrared and ultraviolet spectrophotometry to detect small amounts of picolines; 3-and 4-picolines and 2,6-lutidine in coal tar are determined by Kimura and Katsumoto (116).…”

Section: Organic Analysismentioning

confidence: 99%

Ultraviolet Absorption Spectrophotometry

Rosenbaum¹

1954

Anal. Chem.

View full text Add to dashboard Cite

THISreview covers the 2-year period since the last one in this series (177) was written. The publication of ultraviolet absorption spectra has continued at a rapid rate. Most of these spectra are obtained for the purpose of studying correlations between structure and spectra, and they are not included in this review. GENERAL TOPICSA theoretical derivation of Beer's law is given by Strong (194,196) who extends the treatment to include the effect of the finite pass-band of the spectrophotometer. The derivation and validity of Lambert's and Beer's laws are discussed by Luck (131) with special attention to a spectrum which consists of overlapping lines. Some examples of apparent deviations from Beer's law• reported by Ungnade, Kerr, and Youse (309) are attributed by Yandenbelt, Henrich, and Bash (311) to low solvent transmittance since they were not observed with 0.02-cm. absorption cells.Rose (176) discusses deviations from Beer's law produced by scattering from suspended particles. A particularly helpful paper by Goldring et al. ( 81) treats the causes of departures from theory in spectrophotometry, principally the instrumental factors.Gridgeman (85) presents the theoretical background for the evaluation of the reliability of photoelectric photometry and includes a critique of the transmittance-ratio method developed by Ringbom.

show abstract

“…In solutions of moderate acidity, rates of decarboxylation depend on the concentration of the un-ionized carboxyl group. 8,9 We expect that the proton on the un-ionized carboxyl group will prevent direct formation of CO 2 , requiring an alternative mechanism. Those reactions are likely to proceed via a transition state that occurs after tautomerization of the aromatic carboxylic acid.…”

Section: ■ Introductionmentioning

confidence: 98%

“…In those cases, catalysts can promote decarboxylation by better accommodating the electrons that are gained from the bond that is broken upon release of CO 2 . − An alternative pattern occurs in the decarboxylation of activated benzoic acids. In solutions of moderate acidity, rates of decarboxylation depend on the concentration of the un-ionized carboxyl group. , We expect that the proton on the un-ionized carboxyl group will prevent direct formation of CO 2 , requiring an alternative mechanism. Those reactions are likely to proceed via a transition state that occurs after tautomerization of the aromatic carboxylic acid.…”

Section: Introductionmentioning

confidence: 99%

“…The decarboxylation of 2,4-dimethoxybenzoic acid ( 1 in Scheme ) in highly acidic solutions conforms to the rate law for a specific acid-catalyzed process: , The rate increases with acidity in parallel with the expected extent of formation of the conjugate acid of 1 ( 1H + in Scheme ). ,, For comparison, decarboxylation of 1 under neutral conditions also avoids release of protonated CO 2 . However, that process results from passage through a reactive tautomeric form ( 2 in Scheme ).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Carbon Kinetic Isotope Effects and the Mechanisms of Acid-Catalyzed Decarboxylation of 2,4-Dimethoxybenzoic Acid and CO₂ Incorporation into 1,3-Dimethoxybenzene

et al. 2017

View full text Add to dashboard Cite

The rate of decarboxylation of 2,4-dimethoxybenzoic acid (1) is accelerated in parallel to the extent that the carboxyl group acquires a second proton (1H). However, the conjugate acid would resist C-C bond breaking as that would lead to formation of doubly protonated CO. An alternative via formation of a higher-energy protonated phenyl tautomer (2H) prior to C-C bond breaking would produce protonated CO, an energetically inaccessible species that can be avoided by transfer of the carboxyl proton to water in the same step. Headspace sampling of CO that evolves in the acid-catalyzed process and analysis by GC-IRMS gives a smaller than expected value of 1.022 for the carbon kinetic isotope (CKIE), k/k. While this value establishes that C-C cleavage is part of the rate-determining process, intrinsic CKIEs for decarboxylation reactions are typically greater than 1.03. Computational analysis of the C-C bond cleavage from 2H gives an intrinsic CKIE of 1.051 and suggests two partially rate-determining steps in the decarboxylation of 1: transfer of the second carboxyl proton to the adjacent phenyl carbon and C-C cleavage in which the carboxyl proton is also transferred to water. Applying the principle of microscopic reversibility to fixation of CO in acidic solutions reveals the importance of proton transfers to both carbon and oxygen in the overall fixation process.

show abstract

The Kinetics of the Decarboxylation of 2,4,6-Trihydroxybenzoic Acid in Perchloric Acid Solution

Cited by 19 publications

References 0 publications

Kinetics and mechanism of the decarboxylation of salicylic acids

Kinetics and mechanism of the decarboxylation of salicylic acids

Ultraviolet Absorption Spectrophotometry

Carbon Kinetic Isotope Effects and the Mechanisms of Acid-Catalyzed Decarboxylation of 2,4-Dimethoxybenzoic Acid and CO₂ Incorporation into 1,3-Dimethoxybenzene

Contact Info

Product

Resources

About

The Kinetics of the Decarboxylation of 2,4,6-Trihydroxybenzoic Acid in Perchloric Acid Solution

Cited by 19 publications

References 0 publications

Kinetics and mechanism of the decarboxylation of salicylic acids

Kinetics and mechanism of the decarboxylation of salicylic acids

Ultraviolet Absorption Spectrophotometry

Carbon Kinetic Isotope Effects and the Mechanisms of Acid-Catalyzed Decarboxylation of 2,4-Dimethoxybenzoic Acid and CO2 Incorporation into 1,3-Dimethoxybenzene

Contact Info

Product

Resources

About

Carbon Kinetic Isotope Effects and the Mechanisms of Acid-Catalyzed Decarboxylation of 2,4-Dimethoxybenzoic Acid and CO₂ Incorporation into 1,3-Dimethoxybenzene