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The hydrolyses of benzaldehyde diethyl acetal. benzophenone diethyl ketal, and methyl 2,5-anhydro-a-~-arabinofuranoside are shown to be specific-acid catalysed.ACETAL hydrolysis 1 is a classic example of a specific-acid catalysed reaction. Brprnsted and Wynne-Jones,2 using formic acid-formate buffers (concentration of formic acid 0.0037-0.1194~) were unable to detect any buffer catalysis in the hydrolysis of diethyl acetal. Brprnsted and Grove3 showed that phenol (up to 0.20M) did not increase the rate of hydrolysis of dimethyl acetal in 0-0294~-perchloric acid and that chloroacetic and acetic acid have no effect on the hydrolysis of 2-methyl-1,3dioxolan in 0.05 and OW75~-perchloric acid. Kreevoy and Taft4 found a slight dependence of the rate of hydrolysis of dimethyl acetal on buffer concentration with formate buffers in 50% aqueous dioxan but since the experiments were not performed at constant ionic strength, this could have been due to a salt effect. Koehler and Cordes 5 studied the hydrolyses of 2,2-dimethoxypropane and acetophenone diethyl ketal in carboxylic acid buffers and found only slight decreases in rate with increasing buffer concentration.Orvik and Schubert6 demonstrated that the rate of hydrolysis of 2-(~-methoxyphenyl)-1,3-dioxolan in aniline-anilinium buffers (pH = 4.66) increased nonlinearly with increasing buffer concentration. This catalysis, assumed to be kinetically general-acid catalysis, was considered to arise from capture by aniline of a reversibly formed carbonium ion? Similarly Fife 8 has shown that the rate of hydrolysis of 2-(*-methoxyphenyl) -3,3,4,4-t e tr ame t hyl-1,3-dioxolan increases slightly with buffer concentration in formate buffers.

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