微波消解-氢化物发生原子荧光法测定塑料原料及其制品中的砷、汞

采用微波消解进行样品前处理，以硫脲为预还原剂，用氢化物发生原子荧光法测定塑料原料及其制品中的砷、汞。测定砷和汞的线性范围均为0～8μg／L，砷、汞的检出限分别为0．005、0．076μg／L，测定结果的相对标准偏差分别为4.96％～7．38％、2．94％～7．20％(n=6)，回收率分别为92．0％～103．2％、92．0％～98.0％。     

Asymmetric Henry reaction catalyzed by C2-symmetric tridentate bis(oxazoline) and bis(thiazoline) complexes: metal-controlled reversal of enantioselectivity

[reaction: see text] C(2)-symmetric tridentate bis(oxazoline) and bis(thiazoline) ligands with a diphenylamine backbone have been investigated in the catalytic asymmetric Henry reaction of alpha-keto esters with different Lewis acids. Their Cu(OTf)(2) complexes furnished S enantiomers, while Et(2)Zn complexes afforded R enantiomers, both of them with higher enantioselectivities (up to 85% ee). Reversal of enantioselectivity in asymmetric Henry reactions was achieved with the same chiral ligand by changing the Lewis acid center from Cu(II) to Zn(II). The results show that the NH group in C(2)-symmetric tridentate chiral ligands plays a very important role in controlling both the yields and enantiofacial selectivity of the Henry products.     

胺类化合物气相色谱保留指数与结构的相关性研究

应用Ａｍ指数和引力指数Ｇ１对在３种体系下的胺类化合物的气相色谱保留指数和结构进行了相关性研究,并运用最佳子变量集算法和人工神经网法进行了计算分析,在非极性固定相ＯＶ－１０１和极性固定相ＯＶ－２２５和ＮＧＡ下均获得了比较好的相关模型。     

固定pH滴定法测定弱酸弱碱性药物

报道一种水溶液吕测定弱酸弱碱性药物的新型滴定分析方法－固定ｐＨ滴定法，其理论基础是弱酸弱碱在水溶液中各种存在形式的分布系数在ｐＨ值固定时为常数，对甲硝唑，盐酸美西律等离散常数在１０＾－８至１０＾－１１范围内的７种弱酸弱碱性药物进行测定。结果与药典法吻合，回收率在９９．４％～１００．６％，方法简便，快速，准确，制剂中的赋形剂及色物不影响测定。     

STUDY OF ACOUSTIC EMISSION DURING NON-ISOTHERMAL CRYSTALLIZATION OF POLYPROPYLENE

In this paper we have presented the results of acoustic emission (AE) during non-isothemal crystallization of polypropylene (PP) melt with mean cooling rate 4℃/min, and discussed the effects of molecular weight (MW) on AE activity. It is shown that the amount of AE ring-down counts during whole crystallization of PP depends on the MW strongly.The copious AE bursts have been observed at the late stage of PPcrystallization. AE bursts are caused by cracking, crazing and cavitation between spherulites and inside spherulites.     

Completely geometrically optimized DFT/ONIOM triple-helical collagen-like structures containing the ProProGly, ProProAla, ProProDAla, and ProProDSer triads

We report completely optimized ONIOM DFT/AM1 molecular orbital calculations on several collagen-like triple helices based upon the repeating triad, ProProGly. The requirement of Gly as every third amino acid in collagen can be attributed to its enantiomorphic nature, as it behaves as a Damino acid in collagen. We, therefore, explored related collagen-like triple helices with one of the central Gly's mutated to either L or DAla; l-Ala appreciably destabilizes, while d-Ala slightly stabilizes the triple helical structure. Mutation of the same Gly to DSer, which is simply DAla with an OH in place of one of the methyl H's, induces a much greater stabilization due to an additional H-bond formed between this OH and a C=O on an adjacent peptide strand. Energies are presented for the triple helices and their component strands (both optimized and distorted to their triple helical geometries) relative to the component amino acids. The variation of relative energies with the chosen reference is delineated.     

Efficient and mild benzoin condensation reaction catalyzed by simple 1-N-alkyl-3-methylimidazolium salts

The benzoin reaction, catalyzed by simple 1-N-alkyl-3-methylimidazolium salt-based ionic liquid via carbene intermediate, to give the α-hydroxyl ketone proceeds in CH₂Cl₂ under mild conditions.     

Spiro(benzoxasilole) catalyzed polymerization of oxetane derivatives

A spiro(benzoxasilole) catalyst, 3,3,3′,3′-tetrakis(trifluoromethyl)-1,1′-(3H,3H′)-spirobis(1,2-benzoxasilole) was used to polymerize 3,3-R,R′-oxetanes: BEMO (R, R′ = ethoxymethyl), AMMO (R = azidomethyl, R′ = methyl), NMMO (R = nitratomethyl, R′ = methyl), BAMO (R, R′ = azidomethyl), and BCMO (R, R′ = chloromethyl) with descending rates in this order. ³¹P-NMR of polymerization mixtures quenched using Bu₃P are consistent with an oxonium ion propagating species. Water is not a cocatalyst because it increases the induction period which is not eliminated by the proton trap 2,6-di-t-bu-tylpyridine. The propagating chains were terminated by transfer with the ether oxygen of the polymer either intermolecularly or intramolecularly. The index of propagation to chain transfer, Kk_ik_p/k_tr, varies over more than three orders of magnitude for BEMO > AMMO > NMMO > BAMO. However, k_p/k_tr for the four monomers differ by less than a factor of five indicating the same factors are affecting propagation and chain transfer. Addition of benzyl alcohol and propandiol produced poly(BEMO) having one and two hydroxyl termini, respectively. These telechelic polymers can be used to synthesize linear triblock or multiblock copolymers of oxetane derivatives. © 1992 John Wiley & Sons, Inc.     

The Synthesis and Structure of Silica-Sodalite from Nonaqueous Systems

A silica polymorph, silica-sodalite was synthesized from a nonaqueous system NaOH-SiO2-C2H4(OH)2 and its chemical compositionwas determined to be Si12 O24,2C2H4(OH)2 by the X-fluorescence,thermogravimetric and organic elemental analyses. The single crystal X-ray diffraction structure determination of the silica-sodaliteshowed that the silica-sodalite is cubic, spacing group I23 and unitcell parameter a= 8.8354A. The IF and solid state high resolution Siand 13 C NMR spectra of the silica-sodalite were measured and discussed .     

甲基丙烯酸三丁基锡和甲墓丙烯酸异戊酯共聚合参数的测定

有机锡聚合物兼具杀菌防腐的生物活性功能和一般高分子材料的结构功能，有着潜在的应用前景［１］。本工作应用Ｘ射线萤光光谱测定甲基丙烯酸三丁基锡（ＴＢＴＭ）和甲基丙烯酸异戊酯（ＩＰＭＡ）共聚物中锡的含量。方便，迅速地获得了该共聚物的组成，计算了ＴＢＴＭ和ＩＰＭＡ在四氢呋喃中，５５℃下共聚合的竞聚率，其结果分别为０．２９和０．２４。