Kinetic Isotope Effects in H and D Abstraction Reactions from Alcohols by D Atoms in Aqueous Solution
摘要:
Electron paramagnetic resonance free induction decay attenuation measurements were performed in the range of liquid D2O for the reactions of D atoms with undeuterated and deuterated alcohols. Excellent Arrhenius behavior represented by log(k/M-1 s(-1)) = (10.97 +/- 0.14) - [(24.7 +/- 0.8) kJ mol(-1)/2.303RT)] for CH3OD, log(k/M-1 s(-1)) = (11.09 +/- 0.12) - [(20.8 +/- 0.6) kJ mol(-1)/2.303RT)] for CH3CH2OD, log(k/M-1 s(-1)) = (11.45 +/- 0.10) - [(28.4 +/- 0.6) kJ mol(-1)/2.303RT)] for CD3CD2OD, log(k/M-1 s(-1)) = (11.32 +/- 0.15) - [(21.3 +/- 0.8) kJ mol(-1)/2.303RT)] for CH3CH2CH2OD, log(k/M-1 s(-1)) (11.60 +/- 0.06) - [(21.2 +/- 0.3) kJ mol(-1)/2.303RT)] for(CH3)(2)C(H)OD, log(k/M-1 s(-1)) = (11.48 +/- 0.12) - [(24.7 +/- 0.7) kJ mol(-1)/2.303RT)] for(CD3)(2)C(D)OD, was found in all cases. Compared with the gas phase, the reactions exhibit slightly higher activation energies, in agreement with expectation for solvation based on a predicted decrease of the dipole moment from the reactant alcohol to the transition state. A pronounced increase in Arrhenius preexponential factors is attributed mostly to equilibrium solvation of the D atom, but a significant difference between H2O and D2O suggests contributions of a dynamic solvent effect.
Surface-mediated isomerization and oxidation of allyl alcohol on copper(110)
作者:Robert L. Brainard、Cynthia G. Peterson、Robert J. Madix
DOI:10.1021/ja00195a003
日期:1989.6
3})CHsub2}O-)sub (a)} and complete hydrogenation to CHsub 3}CHsub2}CHsub2}Osub (a)}. Propanal forms at 320 K via further reaction of these oxametallacycles. Evidence for a pi}-bonded allyl oxide CHsub2}double bond}CHCHsub2}Osub (a)}, which is more stable than n-propoxide (CHsub 3}CHsub2}CHsub2}Osub (a)}) toward beta}-hydride elimination, is presented. This allyl oxide decomposes
Heterogeneous<sup>1</sup>H and<sup>13</sup>C Parahydrogen‐Induced Polarization of Acetate and Pyruvate Esters
作者:Oleg G. Salnikov、Nikita V. Chukanov、Larisa M. Kovtunova、Valerii I. Bukhtiyarov、Kirill V. Kovtunov、Roman V. Shchepin、Igor V. Koptyug、Eduard Y. Chekmenev
DOI:10.1002/cphc.202100156
日期:2021.7.2
1-13C-enriched forms with parahydrogen over Rh/TiO2 catalysts in methanol-d4 and in D2O. The maximum obtained 1H polarization was 0.6±0.2 % (for propyl acetate in CD3OD), while the highest 13C polarization was 0.10±0.03 % (for ethyl acetate in CD3OD). Hyperpolarization of acetate esters surpassed that of pyruvates, while esters with a triple carbon-carbonbond in unsaturated alcoholic moiety were less
[1- 13 C]超极化羧酸盐(最显着的是[1- 13 C]丙酮酸盐)的磁共振成像使人们能够观察肿瘤和其他病理中的异常代谢。在此,我们利用仲氢对未同位素标记和1- 13 C 富集形式的相应乙烯基、烯丙基和炔丙基前体进行非均相氢化,研究了具有乙基、丙基和烯丙醇部分的乙酸酯和丙酮酸酯的 1 H 和13 C 超极化效率在Rh/TiO 2催化剂上,在甲醇-d 4和D 2 O中。获得的最大1 H极化为0.6±0.2 %(对于CD 3 OD中的乙酸丙酯),而最高13 C极化为0.10±0.03 %(对于 CD 3 OD中的乙酸乙酯)。醋酸酯的超极化超过了丙酮酸酯,而不饱和醇部分中具有碳-碳三键的酯作为仲氢诱导极化前体的效率低于具有双键的酯。在所研究的化合物中,观察到乙酸丙酯的最大1 H 和13 C NMR 信号强度。乙酸乙酯产生的 NMR 信号强度稍弱,但明显强于所研究的其他酯。
Study of the Mechanism for the Hydrolysis of Alkoxy(aryl)(phenyl)-<b><i>λ</i></b><sup>6</sup>-sulfanenitriles, ArPhS(OR)(N)
The hydrolysis of alkoxy(aryl)(phenyl)-λ6-sulfanenitriles in several buffer solutions was found to follow a good pseudo-first-order kinetic equation, giving the corresponding sulfoximides and alcohols (for the case of the hydrolysis of neopentyloxy-λ6-sulfanenitrile, giving a rearranged product, 2-methyl-2-butanol). The dependence of the rate of hydrolysis on the structure of the alkyl group showed
发现烷氧基(芳基)(苯基)-λ6-硫腈在几种缓冲溶液中的水解遵循良好的准一级动力学方程,得到相应的亚砜酰亚胺和醇(对于新戊氧基-λ6-的水解)磺腈,得到重排产物,2-甲基-2-丁醇)。水解速率对烷基结构的依赖性显示出与通常的 SN2 特征相反的趋势,即 Me < Pr < Bu ≈ Et < i-Pr,除了新戊基。pH 速率曲线表明,在 pH 值大于 6.08 时,水解速率在 [H+] 中也是一级的,并且在低 pH 值时趋于饱和。根据这些动力学结果,提出了两步反应机制,包括烷氧基-λ6-硫腈的氮原子上的预平衡质子化,然后根据烷基的结构,通过烷基碳原子上的 SN2 或 SN1 机制决定速率的 CO 键断裂。从 1/kobs 与 1/[...
Isotope effects in the base cleavage of (dihalomethyl)trimethyltins. Additional evidence for proposed mechanistic pathways
作者:W. Stanczyk、J. Chojnowski
DOI:10.1016/s0022-328x(00)92673-1
日期:1980.12
Solvent deuterium isotope effects on the reaction rate (RIE) and on the isotopic composition of the product (PIE) were studied for the three component reactions of the base cleavage of (dihalogenomethyl)trimethyltins(Me3SnCHX2; X Cl, Br) in 8/2 v/v n-propanol/water in the presence of ammonia buffer. The results support the mechanisms in which free carbanions are separated in the rate determining
研究了溶剂氘同位素对反应速率(RIE)和产物同位素组成(PIE)的影响,研究了(二卤代甲基)三甲基锡(Me 3 SnCHX 2; XCl,Br)的三价反应在氨水缓冲液中于8/2 v / v正丙醇/水中溶解。结果支持了在涉及溶剂共轭碱,scb的反应的速率确定步骤中分离出游离碳负离子的机理,同时证实了在亲和过程中由氨气催化的亲电助溶剂的重要性(通用基地)。
Khatoon, T.; Edelbuettel-Einhaus, J.; Hoyermann, K., Berichte der Bunsen-Gesellschaft, 1989, vol. 93, p. 626 - 632
作者:Khatoon, T.、Edelbuettel-Einhaus, J.、Hoyermann, K.、Wagner, H. Gg.