一种基于形成杂多核络合物的荧光增敏效应的研究 Ⅲ.锰(Ⅱ)、钴(Ⅱ)的混合荧光增敏及其连续测定

本文研究了Mn~(2+)和Co~(2+)对7-(8-羟基-3,6-二磺基萘偶氮)-8-羟基喹啉-5-磺酸-硼砂反应体系的混合荧光增敏作用。实验条件下,荧光增敏强度满足线性加和关系的范围是:Mn~(2+)浓度0～2.9×10~(-7)mol/L;Co~(2+)浓度0～8.8×10~(-7)mol/L;总浓度不超过1.0×10~(-6)mol/L。检出限量为Mn~(2+)4.5×10~(-9)mol/L和Co~(2+)1.4×10~(-8)mol/L。实现了Mn~(2+)和Co~(2+)的连续测定。     

枳壳炮制前后微量元素的测定

采用等离子体原子发射光谱法对枳壳进行了炮制前后32种微量元素含量的测定比较．结果表明:枳壳经麸炒后，微量元素的含量有不同程度的变化。为深入研究枳壳炮制机理提供了参考依据．     

铜在3%NaCl溶液中腐蚀行为的光电化学研究

Cu以其优异的导电性、导热性和易加工性广泛用于工农业生产中．自然Cu的腐蚀和防腐成为人们很关注的问题．人们已经注意到，Cl-对Cu的腐蚀有影响，并进行过一些研究．但目前使用光电化学方法研究这一问题的文章尚不多见，特别是利用测量开路光电压及其瞬态波形这一现场的、无损的、灵敏的监测方法研究户对Cu电极腐蚀全过程的文章尚未见到．本文正是利用如上方法及XPS，AES方法，研究了Cl-对Cu电极腐蚀的全过程，取得了一些有意义的结果．1实验方法Cu电极用99．99％（质量分数）的Cu制成，面积约为39mm2；电极底部由Cu导线焊接引出，…     

α-Oxo Ketene Dithioacetals Chemistry-A Facile Route to the Synthesis of Fused Heterocyclic Compounds

Q-Oxo ketene dithioacetals and related compounds are versatile synthons in organicsynthesis'-'. The substitution reaction of or-oxo ketene dimethylthio acetals with diamineis one of the impel'tant applications for the synthesis of corresponding a-oxo ketenecyclic N, N-acetals. Junjappa and co-workers described this reaction ill a review'.However, since some kinds of ketene dimethylthio acetals are not easy to prepare, themethod melltioned above is limited. Zhu and co-workers had successfully…     

Canon-π Interactions. Synthesis and Crystal Structure of Palladium Complex:[K(DB18C6)]_2[Pd(SCN)_4]

Noncovalentinteractionsplayadominantroleinmanyforefrontareasofmodemchemistry,frommat6rialsdesigntOmolecularbiology.Recelltly,theK -ninteractionshaveattractedmuchattentionbecauseoftheionseleCtivityinpotaSsiumchannelsl.Inothersystem,Sunneretal.showedthefirsttimebymassspectrometrythatK bindstobenzeneinthegasPhase:.ThisfindingstimulatedthestUdyoftheK -xinteractions.Indeed,theK -ninteractalshavealsobeen,identifiedbyX-raysinglecrystaldistractionanalysisforseveralcompouxtds:Km-be~usor--Phenyl',…     

Preconcentration and separation of trace Pd(II) and Pt(IV) with silica gel bonded by aminopropyl-benzoylazo-4-(2-pyridyl-azo)-resorcinol

This paper reports a simple and highly selective method for preconcentrating and separating of trace Pd(II) and Pt(IV) with silica gel bonded by aminopropyl-benzoylazo-4-(2-pyridy-lazo)-resorcinol (ABPR-SG). ABPR-SG is stable in solution from 6 mol/L HCl to pH 7.0 and in common organic solvents. The maximum adsorptive capacity of Pd(n) on ABPR-SG is 362 μmol/g. After preconcentration and separation by using ABPR-SG column, Pd(II) and Pt(IV) of μg/L level in artificial water samples can be measured reliably by common spedrophotometry. The maximum concentration factors of Pd(II) and Pt(IV) on ABPR-SG column are 143 and 125 respectively. The chromatographic column packed with ABPR-SG can be reused. The method is simple and efficient.     

Synthesis and 1H NMR study of 3,4-di ethyl-1,2,3,3a,4,5-hexahydro-canthinone-6

The racemic mixtures of the two epimers of 3,4-diethyl-l,2,3,3a,4,5-hexahydro-canthinone-6 (3,4-diethyl-2,3,3a,4,5,6-hexahydro-6-oxo-1H-indolo-(3,2,1 ,de) (1,5)naphtyridine) have been prepared. They were separated by crystallization of one of the synthesis intermediates. Identification of the configuration was possible by 1h NMR spectroscopy after running a 2D J-resolved spectrum of the “cis”-isomer.     

Studies related to cephalosporins. Part 2 . Displacement reactions on 3-bromomethylcephems with salts of carboxylic acids

The reactivity of Δ³- and Δ²-3-bromomethylcephems toward carboxylate nucleophiles has been studied. The Δ³-bromomethylcephem 1 , less reactive than the Δ²-analogue 4 , is converted in high yields into 3-acyl-oxymethyl-3-cephems 2a-d , generally with no isomerization of the double bond, only within a narrow range of conditions. In particular, the Δ³-7-aminocephalosporanic acid (7-ACA) derivative 2a has been obtained as the only product in 91% yield by treatment of 1 with triethylammonium acetate in acetic acid. The Δ²-bromomethyl-cephem 4 is easily converted into the Δ²-acyloxymethyl-cepheras 5a-d without double bond isomerization, in very high yields.     

Enhanced aromaticity of the transition structures for the diels-alder reactions of quinodimethanes: evidence from ab initio and DFT computations

The Diels-Alder reactions of various quinodimethanes with ethylene are studied by means of ab initio molecular orbital and density functional theory (DFT) to show the effect of aromaticity on the reaction path. The calculations reveal that these reactions are both kinetically and thermodynamically much more favored than the prototype butadiene-ethylene Diels-Alder reaction due to the aromatization process in the transition state (TS) and product. A progressive aromaticity gain is noticed during the reaction, and hence the partial pi-delocalized peripheral diene ring function is coupled with the six-electron sigma,pi-delocalized cyclic unit resulting in an enhanced aromaticity of the TS. The magnetic criteria such as magnetic susceptibility exaltation and nucleus independent chemical shift provide definitive evidence for and fully support the aromatization process and the aromaticity of the TS. The extent of sigma-pi delocalization and the bond make-break at the TS are consistent with each other, and this is strongly influenced by the adjacent pi-aromatization process. Moreover, the aromaticity trends in the resulting TSs and products parallel the activation and reaction energies; the extent of aromatization increases with increasing reaction rate and exothermicity. This confirms that aromaticity is the driving factor governing cycloadditions involving quinodimethanes.     

Isolation of pure (2S,1'S,2'S)-2-(2'-carboxycyclopropyl)glycine from Blighia sapida (Akee)

The isolation of (2S,1'S,2'S)-2-(2'-carboxycyclopropyl)glycine (CCG I, 2) from Blighia sapida (Akee) was achieved through column chromatography on deactivated silica gel followed by ion-exchange chromatography. A HPLC method has also been devised in order to assess the purity of the isolated product.