A Kinetic Isotope Effect Study on the Hydrolysis Reactions of Methyl Xylopyranosides and Methyl 5-Thioxylopyranosides: Oxygen versus Sulfur Stabilization of Carbenium Ions
作者:Deepani Indurugalla、Andrew J. Bennet
DOI:10.1021/ja011232g
日期:2001.11.1
(J. Am. Chem. Soc. 1986, 108, 7287-7294) KIEs for the acid-catalyzed hydrolysis of methyl alpha- and beta-glucopyranosides, it is possible to conclude that at the transition state for xylopyranoside hydrolysis resonance stabilization of the developing carbenium ion by the ring oxygen atom is coupled to exocyclic C-O bond cleavage, and the corresponding methyl glucopyranosides hydrolyze via transition
以下动力学同位素效应 KIEs (k(light)/k(heavy)),分别在 HClO(4) (mu = 1.0 M, NaClO( 4)) 在 80 摄氏度:alpha-D,1.128 +/- 0.004,1.098 +/- 0.005;β-D, 1.088 +/- 0.008, 1.042 +/- 0.004; 伽马-D(2)、(C5) 0.986 +/- 0.001、0.967 +/- 0.003;离去基团 (18)O, 1.023 +/- 0.002, 1.023 +/- 0.003; 环 (18)O, 0.983 +/- 0.001, 0.978 +/- 0.001; 异头 (13)C, 1.006 +/- 0.001, 1.006 +/- 0.003; 和溶剂,0.434 +/- 0.017、0.446 +/- 0.012。结合报道的 (J. Am. Chem. Soc. 1986