63860-13-9Relevant academic research and scientific papers
Reactions of Thiols with Phenylglyoxal to Give Thiomandelic S-Esters Formation of Hemithioacetals and Their Rearrangement
Okuyama, Tadashi,Kimura, Kazumasa,Fueno, Takayuki
, p. 1493 - 1497 (2007/10/02)
Equilibrium constants Kh for the addition of 2-mercaptoethanol and glutathione to phenylglyoxal to form hemithioacetals were determined spectrophotometrically over the pH range 7-10.The observed Kh values decrease sigmoidally with pH as the thiol ionizes.Rearrangement of hemithioacetals formed from phenylglyoxal and various thiols was kinetically investigated.The rates increase with thiol concentration following a saturation curve to give Kh identical with the spectrophotometric value.The rearrangement is subject to general base catalysis.The solvent isotope effect on the rate of the rearrangement, kH2O/kd2O, is nearly 1.0; that on the equilibrium, KH2Oh/KD2Oh, is 0.38.The results strongly support the mechanism involving proton transfers through an enediol intermediate.
Mechanism of Hydrolysis of Hydroxy Thiolesters in the Presence of Boric Acid
Okuyama, Tadashi,Nagamatsu, Hiroaki,Fueno, Takayuki
, p. 1336 - 1342 (2007/10/02)
The catalytic effect of boric acid on the hydrolysis of S-butyl 2-hydroxy-2-phenylthioacetate (thiomandelate, 1) and 3-hydroxy-3-phenylthiopropionate (2) has been investigated in aqueous solution.The catalytic constants increased sigmoidally with increasing pH, the pKa of the curve being 9.2 for both 1 and 2.Approximate Hammett ρ values were 1.2 and 0.6 for the alkaline and borate-catalyzed hydrolyses of ring-substituted derivatives of 1, respectively.Boric acid did not show any specific influence on the hydrazinolysis of 1.Thise results lead to the conclusion that the borate catalysis occurs through an intramolecular transfer of the boron-coordinated hydroxide ion to the carbonyl carbon within a borate-substrate complex.
