聚乙烯醇基质树脂的羧基化及其对l-赖氨酸的吸附

醋酸乙烯酯与异氰尿酸三烯丙酯经悬浮聚合后醇解制备的聚乙烯醇基质树脂,有较好的亲水性,将其含有的羟基进行羧基功能基化,制备了3种不同基团的羧基树脂,用化学滴定法测定了树脂的羧基含量,基质树脂的羟基转化率分别为PVA-CM为20.0%、PVA-SuA为47.6%、PVA-TPA为57.2%。3种羧基化树脂及基质树脂对赖氨酸的吸附性能用静态吸附等温线方法测定。结果表明,25℃在2.0~80.0mmol/L浓度范围内树脂对赖氨酸的吸附等温线符合Freundlich方程;吸附能力顺序为PVA-SuA>PVA-CM>PVA>PVA-PTA。考察了羧丙酸酯树脂PVA-SuA对初始浓度为50.90mmol/L赖氨酸的吸附动力学。实验结果表明,其对赖氨酸的吸附符合二级动力学模型。     

pH Neutralization while Succinic Acid Adsorption onto Anion-Exchange Resins

Succinic acid is a useful chemical and its purification from fermentation broth by ion-exchange resins has widely drawn attention. In this study, pH neutralization in the process of adsorption of succinic acid from model solutions and fermentation broth by anion-exchange resin NERCB 04 has been tested. Adsorption capacity of NERCB 04 was about 0.41 g succinic acid/g resin at concentrations of succinic acid in the range of 10–50 g/L in packed column. In the process of succinic acid removal, pH of the system could also be neutralized. The neutralizing ability of the resin as a neutralizing agent has also been studied in the model cycle system and in the real fermentation cycle process. It was found that NERCB 04 showed stable adsorption capacity and pH neutralization ability after each regeneration. A certain amount of anion-exchange resin could neutralize the low pH values (pH 2–5) and maintain the system around pH 7.0. This means the anion-exchange resins have the function of neutralizing reagent in the process of adsorbing succinic acid.     

Adsorption of Biologically Active Carboxylic Acids on a Copper Electrode

The adsorption of salicylic, acetylsalicylic, ascorbic, and nicotinic acids on a copper electrode has been studied in the cathodic range of potentials. These acids are adsorbed as either anions or neutral molecules, depending on the electrode potential. The characteristics of the adsorption process are connected with the structure and degree of dissociation of the acids and also on the presence of oxygen in the solution.     

芳香氨基酸在吸附树脂上的传质速度的研究

本文建立了测量芳香氨基酸在吸附树脂上传质速度的方法。引用Boyd方程模型测定了苯丙氨酸和酪氨酸的有效内扩散系数;研究了树脂结构与芳香氨基酸扩散速度之间的关系;同时考察了温度、pH值诸因素对扩散速度的影响。     

Transport of Acids through Polyether-Sulfone Anion-Exchange Membrane

Diffusion dialysis of sulfuric acid and hydrochloric acid into water with a polyether-sulfone anion-exchange membrane was studied. Transport of sulfuric acid and hydrochloric acid through the membrane has been quantified by diffusion coefficients and mass transfer coefficients. The mass transfer coefficients were investigated as a function of the rotational speed of the stirring rate of both sides of the membrane and with different pH ranges. It was observed that the diffusion dialysis seems to be dependent on the rotational speed of the stirrer; in contrast, the membrane mass transfer coefficients are independent of rotational speed, but they are slightly affected by the initial acid concentration in donor phase. Copyright 2001 Academic Press.     

大孔吸附树脂的吸附机理

大孔吸附树脂(macroprous adsorption resin, MAR)是近几十年发展起来的一种具有多孔立体结构、人工合成的有机高分子聚合物。由于其特殊的理化性质和吸附性能,已被广泛应用于化学、医药、环保和食品等领域。本文介绍了近年来国内外对大孔吸附树脂在吸附机理研究方面的进展,重点介绍了不同温度条件下大孔吸附树脂对靶标分子的吸附热力学行为模式,靶标分子在大孔吸附树脂表面及孔内的吸附扩散行为模式。此外,大孔吸附树脂性能参数和靶标分子结构参数之间构效关系也对其吸附选择性规律具有重要的影响。因此,大孔吸附树脂与底物间构效关系的匹配程度及其对选择性的影响是大孔吸附树脂分离理论研究的核心。本文最后介绍了可以准确客观描述吸附过程并具有一定使用范围的大孔吸附树脂吸附模型的建立和评价。     

Activation of Carboxylic Acids in Asymmetric Organocatalysis

Organocatalysis, catalysis using small organic molecules, has recently evolved into a general approach for asymmetric synthesis, complementing both metal catalysis and biocatalysis. 1 Its success relies to a large extent upon the introduction of novel and generic activation modes. 2 Remarkably though, while carboxylic acids have been used as catalyst directing groups in supramolecular transition‐metal catalysis, 3 a general and well‐defined activation mode for this useful and abundant substance class is still lacking. Herein we propose the heterodimeric association of carboxylic acids with chiral phosphoric acid catalysts as a new activation principle for organocatalysis. This self‐assembly increases both the acidity of the phosphoric acid catalyst and the reactivity of the carboxylic acid. To illustrate this principle, we apply our concept in a general and highly enantioselective catalytic aziridine‐opening reaction with carboxylic acids as nucleophiles.     

Determination of Low Molecular Weight Carboxylic Acids in Water by HPLC with Conductivity Detection

Abstract

Low molecular weight carboxylic acids (C₂-C₈) were measured in aqueous samples using reverse phase HPLC coupled with conductivity detection. The aqueous samples are adjusted to pH 2 with H₂SO₄ and extracted with diethyl ether. The ether is allowed to evaporate over distilled water. The acid concentrate is analysed using a Zorbax-ODS column (25 mm × 4.6 mm). The method is simple, fast, and because of the selectivity of the conductivity detector, is relatively free from interferences. Average precision is estimated to be approximately ± 13% for the overall method.     

羧酸的还原方法

羧酸的还原是有机化学中的一类重要反应,有着广泛的用途。氯化铝锂是还原羧酸的常用试剂,但是,该试剂能还原多种官能团,因此选择性较差,近年来,化学工作者研究亲报道了许多新的还原方法,如用NaBH4/I2、NaBH4/H2SO4、NaBH4/BOP体系等还原羧酸成醇以及还原羧酸成醛的特殊方法。本文拟对这些新的研究进展作一介绍。     

Capillary Gas Chromatographic Separation of Carboxylic Acids Using an Acidic Water Stationary Phase

An acidic water stationary phase is used for the analysis of carboxylic acids in capillary gas chromatography (GC). Under regular pH 7 operating conditions, these analytes are largely ionized and elute poorly, if at all, from the water phase. However, by adjusting the phase to pH 2, it is found that various acids are neutralized and can be readily eluted and separated in the system. Sulfamic acid is found to provide a stable pH for the water phase over time, whereas hydrochloric acid and other more volatile additives quickly evaporate from the column. Under optimal low pH conditions, the acidic analytes yield good peak shape and are readily observed for masses investigated down to 5 ng on-column. By comparison, on a conventional non-polar capillary GC column, the same analytes display threefold more peak tailing and are not detected for masses below 30 ng on-column. Through altering the phase pH, it is found that the selectivity between certain analytes can be potentially enhanced depending on their respective pKa values and/or ionizability. The analysis of various different samples containing carboxylic acids is demonstrated and the results indicate that this approach can possibly offer unique and beneficial selectivity in such determinations.     

Microwave-Assisted Esterification of Diverse Carboxylic Acids and Chiral Amino Acids

A facile and efficient synthetic method of esters from their corresponding carboxylic acids and amino acids is described. The esterification reaction of carboxylic acids and amino acids could be greatly accelerated under microwave irradiation because the reactions described in this article took place in only 5 min with almost quantitative yields, and distinct acidity of catalytic acids was well tolerated. Unlike the racemation problem in microwave-assisted N-acylation reactions, the esters of chiral amino acids could be achieved with retention of configuration under this condition.     

分光光度法测定水溶液中的有机酸含量

利用水溶液中的有机酸在高氯酸羟胺(HAP)和N,N′-二环己基碳酰亚胺(DCC)存在的条件下生成的羟肟酸,以及羟肟酸在酸性高氯酸铁溶液中显色的性质,建立了一种分光光度测定水中有机酸含量的方法。对显色剂的酸度、浓度、加入体积、HAP和DCC的浓度、加入体积以及显色反应的温度、反应时间对吸光度的影响进行了考察。结果表明,该显色反应在反应条件:0.0687mol/LHAP1.0mL、0.6mol/LDCC0.5mL、震荡均匀后室温下放置反应15min、0.02mol/L酸性高氯酸铁溶液(高氯酸浓度0.3mol/L)显色条件下具有最大的吸光度;并对正丁酸、正戊酸、苯甲酸进行了线性关系考察。结果表明,该检测方法具有仪器简单、操作方便、线性范围较宽、准确度高等优点,可用于那些不易从水溶液中萃取的有机酸的测定,也可用于液相色谱洗脱液中有机酸的测定。     

Synthesis of Peroxide Monomers Based on Unsaturated Carboxylic Acids

Russian Journal of Organic Chemistry -     

Preparation of Functionalized Esters of Carboxylic Acids

The synthesis of simple esters (methyl, ethyl, etc.) of carboxylic acids is generally a trivial synthetic transformation due to the great variety of mehtods available (CH₂N₂, MeOH-H⁺,Me₂SO₄-Base, copper salts-alkylhalides¹, and CaO with alkylhalides²). However, what was sought in this laboratory were methods for preparation of functionalized esters. Specifically, Investigations are underway to develop methods for intra molecular transfer or intramolecular reaction of the functionalized (“R”) portion of the carboxylic acid ester (as illustrated below).     

乙酸乙酯水溶液中水在3A分子筛上的吸附平衡与动力学

乙酸乙酯水溶液中水在3A分子筛上的吸附平衡与动力学;乙酸乙酯;水;吸附平衡与动力学;表面扩散系数;3A分子筛     

One-Pot Reduction of Carboxylic Acids via O-Acylisoureas

A simple one-pot reduction of aliphatic carboxylic acids to primary alcohols, by treatment with dicyclohexylcarbodiimide followed by lithium borohydride, is reported. The same methodology applied to aromatic carboxylic acids is shown to give a mixture of the alcohols with N-cyclohexylcarboxamides.     

Reaction of N-Cyanotrialkylammonium Fluorborates and Carboxylic Acids

Since the preparation of stable N-cyanotrialkylammonium fluoroborates (1)^2,3 we have been examining the reactions of the salts with a variety of nucleophiles. We wish to report the reactions of the salts with carboxylic acids. In principle there are two pathways for reaction with a nucleophile. Path A, the alkylation reaction, has been known for a long time and is the basis of the von Braun reaction.^4–6 Path B, the cyanation reaction, has been observed or postulated to occur in a few cases in the reaction of cyanogen halides and acids.^6–7