The exchange reaction between H2 18O and acetic, monochloroacetic, dichloroacetic, and trichloroacetic acids

McTigue, PT; Renowden, PV; Watkins, AR

doi:10.1071/ch9700381

Cited by 5 publications

(2 citation statements)

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“…Concerning the present problem, it has been found that fc2(H) = 0.89/z2(D) (which reduces to &2h = 0.7&2d) for acetic acid.5 For CClH2COOH the result is fe2h = 0.6fe2d under similar conditions of dilute acid concentration. 7 The present experiment on TFA suggests that fe2m = 0.7fe2h (deuteration yielding the slower rate constant) in contrast to the inverse result for dilute acetic acid. It is expected that the TFA result reflects a much larger primary contribution to the isotope effect.…”

Section: The Exchange Rate Constantmentioning

confidence: 48%

Kinetics of oxygen-18 exchange between carboxylic acids and water

Redington¹

1976

J. Phys. Chem.

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Using the example of trifluoroacetic acid, infrared matrix-isolation spectroscopy is shown to provide an analytical method for monitoring the oxygen exchange kinetics that occur in solutions of carboxylic acids and water. The method should prove valuable in cases where locating specific 180 labels is important. The spectra demonstrate that the singly 180-labeled acid molecules are generated at equal rates on a macroscopic time scale. The rate equation is followed over large changes of the 180 label for both acid and water molecules. The samples, highly concentrated in CF3COOH, possess approximately equimolar amounts of 160 and 180. Deuteration (50%) reduces the specific rate constant by approximately 30%. Literature data for the oxygen exchange kinetics of CF3COOH, CCI3COOH, CH3COOH, and ClCHs^COOH are reexamined and the rate constants and exchange pathways are discussed. In acidic solutions it appears that the primary exchange pathway is by direct attack of hydronium ion on the neutral acid molecule. The rate constants determined using matrix-isolation spectroscopy are similar to those obtained using mass spectrometric analysis.

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Section: The Exchange Rate Constantmentioning

confidence: 48%

Kinetics of oxygen-18 exchange between carboxylic acids and water

Redington¹

1976

J. Phys. Chem.

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“…The exchange of the oxygen atoms of carboxylic acids and carboxylate ions with solvent water has been extensively studied using an oxygen-18 label. [1][2][3][4][5] In the mass spectrometric studies1-4 it was assumed that exchange went through formation of a tetrahedral intermediate, I-III, which decomposed rapidly to give the exchange products. Bender6 identified similar tetrahedral intermediates for the 180 exchange-hydrolysis reactions of alkyl esters.…”

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confidence: 99%

Tracer studies of carboxylic acids. 7. Oxygen-18 exchange of propionic acid with solvent water and with surfactant solubilized water in benzene

Lomax¹,

O’Connor²

1978

J. Am. Chem. Soc.

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min) showed two major low boilers (89%). By coinjection it was determined that the acetates which result from cleavage of the 2,5 bond (i.e., 9 and 10) comprised <8% of the mixture. The crude acetate mixture was dissolved in 5 mL of ether and treated with 2 mL of methylmagnesium bromide (3 M) at 0 °C for 2 h. The reaction mixture was quenched with 20% NH4C1 and extracted with ether. The crude alcohol mixture thus obtained was directly methylated in 5 mL of THF using 25 m (0.6 mmol) of NaH and 0.4 mL of CH3I. The ether mixture was purified by GLC (6 ft X '/4 in. 20% triscyanoethoxypropane on 60/80 Chromosorb P) and identified as 29b and 30b (1/2.8) by their spectral data and comparison with a sample prepared by a different route.23Acetolysis of the outside,exo-l-OTs was performed at 120 °C for 240 h. Workup and GLC analysis (6 ft X '/s in. 10% Carbowax 20M in 60/80 Chromosorb P, T 151 °C,/30 mL/min) showed a complex mixture of at least four poorly resolved major peaks. The only component which could be isolated from the mixture was identified by comparison with a known sample as the inside, exo-1-OAc. Owing to the complexity of the mixture the reaction was not further investigated.Acetolysis of the outside,exo-2-OTs was performed at 125 °C for 60 h. GLC analysis (10% Carbowax 20M, 145 °C,/ 30 mL/min) showed at least six major products, all poorly resolved. The mixture was not further characterized.Supplementary Material Available: All the spectral data and mass spectroscopic molecular weights (7 pages). Ordering information is given on any current masthead page.

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