Potassium tert-butoxide. Strong base for the nonaqueous visual titration of weak acids
Potassium tert-butoxide. Strong base for the nonaqueous visual titration of weak acids
复制标题
叔丁醇钾。
DOI：
10.1021/ac60336a037
复制
发表时间：
1973
影响因子：
7.4
通讯作者：
H. Bosshard
中科院分区：
文献类型：
--
作者：
S. Ehrlich;H. Bosshard
在合成新氨基酸的过程中，我们需要在其中心碳原子上含有一个弱酸性质子的取代丙二酸酯（1，2）。如果有合适的强无水滴定剂，可通过非水滴定法检查此类化合物的纯度。季铵型氢氧化物已广泛用于弱酸的非水滴定（参见参考文献3、4）。然而，甲醇或痕量的水通常存在于这些碱中，根据我们的经验，这会有害地干扰非常弱酸的滴定。已报道用甲醇钾的二甲基甲酰胺溶液滴定各种烷基化丙二酸酯（5）。本文报道了用叔丁醇钾在叔丁醇-苯（1：1）中目视滴定溶于二甲基甲酰胺（DMF）的弱酸。该滴定剂是一种强无水碱，易于制备，可稳定数月。用2-硝基二苯胺或2-硝基苯胺作指示剂，在DMF中进行了各种丙二酸酯衍生物和其它弱酸性化合物的目视滴定。
In the course of the synthesis of new amino acids we were in need of substituted malonic acid esters (1, 2) which contain a weakly acidic proton at their central car-bon atom. The purity of such compounds might be checked by nonaqueous titration provided a suitably strong anhydrous titrant is available. Quaternary ammo-nium hydroxides have been widely used for the nona-queous titration of weak acids (see, eg, ref 3, 4). How-ever, methanol or traces of water are usually present in these bases which, in our experience, harmfully interferes with the titration of very weak acids. Titration of variously alkylated malonates has been reported with potassium methoxide in dimethylformamide (5). In the present note, we report the visual titration of weak acids dissolved in dimethylformamide (DMF) with potassium tert-butoxide in tert-butyl alcohol-benzene (1: 1). This titrant is a strong anhydrous base, it is easy to prepare and is stable for several months. Visual titrations of various malonic ester derivatives and of other weakly acidic compounds have been carried out in DMF using 2-nitrodiphenylamine or 2-nitroaniline as indicators.