Liquid Ammonia as a Dipolar Aprotic Solvent for Aliphatic Nucleophilic Substitution Reactions
作者:Pengju Ji、John Atherton、Michael I. Page
DOI:10.1021/jo102173k
日期:2011.3.4
free-energy relationships, the ionization constants of phenols ions in liquid ammonia were obtained using UV spectra. These equilibrium constants are the product of those for ion-pair formation and dissociation to the free ions, which can be separated by evaluating the effect of added ammonium ions. There is a linear relationship between the pKa of phenols in liquid ammonia and those in water of slope 1.68
已经确定了各种亲核试剂与取代的苄基氯在液氨(LNH 3)中反应的速率常数。为了充分解释相关的线性自由能关系,使用紫外光谱获得了液氨中酚离子的电离常数。这些平衡常数是离子对形成和离解成游离离子的那些常数,可以通过评估添加的铵离子的作用来分离。p K a之间存在线性关系液氨和坡度为1.68的水中的苯酚的含量 氨离子以无质子化的游离碱形式存在于液氨中,其电离常数无法通过NMR确定。取代苄基氯在25°C的液氨中的溶剂分解速率显示Hammettρ为零,对环取代基的依赖性很小或没有依赖性,这与取代苄基卤化物在水中的水解速率形成鲜明的对比,后者的变化范围为10 7折。苄基氯被取代的酚盐离子的取代率在表示S N 2过程的亲核试剂浓度中是一阶的,并且速率常数对液氨中苯酚的p K a的依赖性产生了布朗斯台德(Brønsted)βnuc = 0.40。与溶剂分解反应相反,酚盐离子与4-取代的苄基氯的反应得到的Hammettρ=
Kinetics and mechanism of the reaction between 4-t-butylphenolate anion and tetrahydroxoargentate(III) in aqueous alkaline media
作者:Rama K. Panda、Louis J. Kirschenbaum
DOI:10.1039/dt9890000217
日期:——
The reaction of [Ag(OH)4]– with 4-t-butylphenolate (L–) follows a biphasic absorbance change, each phase exhibiting pseudo-first-order kinetics under limiting conditions of the silver(III). A subsequent, slow, and very small absorbance increase (t0.5 > 1 h) is accompanied by the precipitation of metallic silver. In the [L–] range 0.5 × 10–3– 10 × 10–3 and [OH–] range 0.12–1.2 mol dm–3 at 25 °C and
A new type of double picket-fence porphyrin, bearing pyrimidine rings at the meso-positions was prepared from the corresponding pyrimidine-5-aldehydes using either Rothemund or McDonald condensation reactions. (C) 1999 Elsevier Science Ltd. All rights reserved.
(Alkoxycarbonyl)- and (aryloxycarbonyl)cobalt carbonyls