The direct conversion of carbamates to ureas using aluminum amides

The conversion of carbamates into ureas using aluminum amide complexes is reported. This reaction is a convenient method to prepare bi-, tri- and tetra-substituted ureas from carbamate-protected primary or secondary amines by reaction with primary or secondary amines in the presence of stoichometric quantities of trimethylaluminum. A reactivity trend of the various carbamates was observed and methyl and benzyl carbamates were reacted selectively in the presence of t-butyl carbamates.     

Preparation and separation of all possible rotamers of a stereochemical analog of meso-tartaric acid: optically inactive and optically active isomers of (R,S)-2,2′-bis(methoxycarbonyl)-6,6′-dimethyl-9,9′-bitriptycyl

All the three possible rotamers of the title compound were separated by chromatography, and unambiguously identified by NMR and X-ray analysis. One of the isomers was optically inactive C_i conformation. The other optical active forms were resolved to give a pair of enantiomers, which were characterized by optical rotation and CD spectra. Thus the optical inactivity of a compound such as meso-tartaric acid that can take C_i conformation in solution, is now ascribed to that the molecule has an optically inactive C_i conformer and equal amounts of optically active conformers, that are enantiomers, in solution.     

Crystal Structures of Lanthanum Complexes with Nitrobenzoic Acids

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GC/MS SIM法快速测定酒中的游离脂肪酸

本文介绍一种简单、快速、灵敏、直接分析酒中游离脂肪酸的测定方法。用涂有OV-17熔融石英毛细管柱。选择游离脂肪酸质谱图中的基峰离子m/z 60进行SIM检测。定量测定了茅台酒、珍酒及鸭溪窖酒中十二种游离脂肪酸。     

红细胞膜上各种磷脂中脂肪酸的测定

应用自制硅胶板的薄层色谱法分离了红细胞膜上四种主要磷脂。将分离后的每种磷脂斑点硅胶涂层刮下，不经萃取，直接在无水甲醇－苯－乙酰氯溶液中进行转移甲基化，然后用毛细管相色谱分离测定其脂肪酸组成和含量。上述方法已成功地用于先天愚型病人和正常人红细胞膜上各种磷脂中脂肪酸轮廓分析，获得有意义的结果。     

植物油的质谱分析：1.蓖麻油

运用一种植物油的系统分析方法测定蓖麻油的精细组分，这包括皂化，ＢＦ３－ＭｅＯＨ甲基化，ＧＣ－ＣＩＭＳ法测定脂肪酸碳链长度和不饱和度，ＡＭＰ衍生化，ＧＣ－ＥＩＭＳ测定不饱和脂肪酸的双链位置，分析了蓖麻油的十一种脂肪酸组分，有五个为未知组分，并测定了其中三个组分的双链位置。     

Keggin型杂多酸在镀锌钝化中的应用

比较了H_4SiMo_(12)O_(40)、H_3PW_(12)O_(40)、H_4SiW_(12)O_(40)、H_3PMo_(12)O_(40)及铬酸盐对镀锌层钝化效果。H_3PMo_(12)O_(40)钝化的最佳条件为:H_3PMo_(12)O_(40)5g/L,pH 1.1,钝化时间35秒,温度15℃,空留时间10秒,封闭温度100℃(水)。经扫描电镜、XPS、AES、IR和Raman光谱等测定,表明在锌表面形成了一种含有P、Mo、O及Zn的耐蚀性膜。其中钼以Mo(Ⅵ)、Mo(Ⅴ)和Mo(Ⅳ)存在,P/Mo比为1:3.0。推测锌表面形成了一种形如Zn_x(PMo_3)_rO_z/ZnO/Zn的复杂钝化膜。     

2-Cyanoacrylates in the conjugate addition of trifluoroacetic acid and nucleophilic reagents

In the presence of trifluoroacetic acid, ethyl 2-cyanoacrylate readily reacts with nucleophilic reagents, such as 2-chloro-1,3,2-benzodioxaphosphole, (EtO)₃P, (EtO)₂PCl, Ph₂PCl, Ph₃P, and thiourea. In these reactions the acid proton enters position 2 of the cyanoacrylate, whereas the nucleophilic component enters position 3, in accordance with the electron density distribution in the acrylate. In the absence of trifluoroacetic acid the above reagents, except 2-chloro-1,3,2-benzodioxaphosphole, cause ethyl 2-cyanoacrylate polymerization. The interaction of ethyl 2-cyanoacrylate with 2-chloro-1,3,2-benzodioxaphosphole and trifluoroacetic acid is the first example of a 2-cyanoacrylate taking part in the acid-initiated electrophilic conjugate addition of a weak nucleophile.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1245–1247, July, 1993.     

镧系(Pr~(3+)、Ho~(3+))-8-羟基喹啉-5-磺酸—氯化十六烷基吡啶体系的导数吸收光谱研究及分析应用

本文用导数分光光度沾测定了镧系(Pr~(3+))、Ho~(3+))与8-羟基喹啉-5-磺酸及氯化十六烷基吡啶体系的零阶及三阶导数吸收光谱,并计算了它们的摩尔吸光系数及摩尔导数吸光系数。提出了一个混合稀土中直接测定镨的方法,该方法的准确度及选择性较好。     

Functionalization of chitosan with 3-nitro-4-amino benzoic acid moiety and its application to the collection/concentration of molybdenum in environmental water samples

A chitosan resin functionalized with 3-nitro-4-amino benzoic acid moiety (CCTS-NABA resin) was newly synthesized for the collection/concentration of trace molybdenum by using cross-linked chitosan (CCTS) as base material. The carboxyl group of the moiety was chemically attached to amino group of cross-linked chitosan through amide bond formation. The adsorption behavior of molybdenum as well as other 60 elements on the resin was examined by passing the sample solutions through a mini-column packed with the resin. After the elution of the elements collected on the resin with 1 M HNO₃, the eluates were analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) and atomic emission spectrometry (ICP-AES).

The CCTS-NABA resin can adsorb several metal ions, such as vanadium, gallium, arsenic, selenium, silver, bismuth, thorium, tungsten, tin, tellurium, copper, and molybdenum at appropriate pHs. Among these metal ions, only molybdenum could be adsorbed almost completely on the resin at acidic regions. An excellent selectivity toward molybdenum could be obtained at pH 3–4. The adsorption capacity of CCTS-NABA resin for Mo(VI) was 380 mg g⁻¹ resin. Through the column pretreatment, alkali and alkaline earth metals in river water and seawater samples were successfully removed.

The CCTS-NABA resin was applied to the adsorption/collection of molybdenum in river water and seawater samples. The concentrations of molybdenum in river water samples were found in the range of 0.84 and 0.95 ppb (ng g⁻¹), whereas molybdenum in seawater was about 9 ppb. The validation of the proposed method was carried out by determining molybdenum in the certified reference materials of SLRS-4, CASS-4, and NASS-5 after passing through the CCTS-NABA resin; the results showed good agreement with the certified values.