The .alpha.-cyano-.alpha.-phenylacetic acid keto-enol system. Flash photolytic generation of the enol in aqueous solution and determination of the keto-enol equilibrium constants and acid dissociation constants interrelating all keto and enol forms in that medium

Flash photolysis of 4-diazoisochroman-3-one in aqueous solution. Hydration of the carbene produced by loss of nitrogen and ketonization of the enol hydration product

“…1 is typical of rate profiles for ketonization of enols of carboxylic acids and esters. 1b, 16,19 It is also consistent with the known mechanism for enol ketonization, which consists of ratedetermining proton transfer from any available acid to the b-carbon atom of the enol or its enolate ion. 20 In aqueous solution at zero buffer concentration the available acids will be the hydronium ion (written here as H ) and water itself, and the reaction scheme may therefore be written as shown in Eqn.…”

100 Years of the Wolff Rearrangement

“…While many acyclic carboxylic acid enols, such as 257, ketonize more rapidly than they are formed, 258 stands out as an observable species. [229] Acylketenes (α-oxoketenes) are remarkably reactive species; [230] their hydration rates compare with those of cyclopentadienylideneketenes. Different types of enols have been detected, depending on ring size, as illustrated by 259 Ǟ 260 [231] and 261 Ǟ 262.…”

Tautomerism of lactones and related compounds. Mass spectrometric data and theoretical calculations

“…12 In addition, for carboxylic acids, the very low relative stability of their enols is a well known fact, 4,13 although some of these short-life tautomers were prepared as intermediate compounds. [14][15][16][17][18][19][20] There are few studies about lactone tautomerism. This family of compounds exhibits great biological interest.…”