流动注射-毛细管电泳直接紫外测定环境水中硝酸根和亚硝酸根

采用流动注射与毛细管电泳联用（FI-CE）接口进行自动连续采样。对检测波长、电渗流改性剂浓度、载流中四硼酸钠浓度、载流PH、载流流速及采样环体积等条件进行优化，并对环境水样中常见阴离子的干扰进行研究，建立了同时测定水中硝酸根和亚硝酸根的方法。在采样量为50μl时硝酸根和亚硝酸根的检出限（3σ）分别为0.2和0.4mg/L；峰高RSD分别为1.6%和2.0%(20mg/L,n=25)，峰面积RSD分别为1.7%和1.6%(20mg/L,n=25)，采样频率为60/h。用本法测定井水水样的结果与离子色谱法一致。水样中加入10mg/L硝酸根和亚硝酸根的回收率为98%-108%。     

2-氨-6-氯嘌呤用于亚硝酸根离子的荧光光度法测定

应用荧光光谱法研究了2-氨-6-氯嘌呤与亚硝酸根离子间的相互作用并建立了亚硝酸根离子测定的新方法.在0.25 mol/L的H2SO4水溶液中,2-氨-6-氯嘌呤分子上的氨基与亚硝酸根离子发生重氮化反应生成重氮盐,重氮盐在沸水浴中加热水解,氨基被羟基取代,产生弱荧光的2-羟基-6-氯嘌呤.此反应导致荧光强度降低且在一定范围内与亚硝酸根离子浓度呈良好的线性关系,据此建立了荧光猝灭法测定亚硝酸根离子的新方法,其线性范围为1.00×10-7 ～1.30×10-5 mol/L,方法检出限为7.54×10-8 mol/L.该方法应用于自来水中亚硝酸根离子的测定,回收率为102% ～110%.     

毛细管离子电泳法同时测定腌菜中硝酸根和亚硝酸根

以溴离子(Br-)为内标,建立了毛细管离子电泳同时测定腌菜中的硝酸根和亚硝酸根的方法。讨论了缓冲液pH、样品和缓冲液中氯化钠浓度、分离电压对分离的影响。结果表明:以含1mol LNaCl的40mmol LH3PO4 NaOH缓冲-、-得到基线分离。NO3-和NO2液(pH3.5)为背景电解质,4min内Br-、NO3-检出限分别为0.1g L和0.3g L,峰面积相对标准偏差分别为4.6%和NO25 8%。     

动力学分光光度法测定痕量亚硝酸根和硫氰酸根的研究

基于亚硝酸根对溴酸钾氧乙基橙反应的催化作用及硫氰酸根对此反应的抑制作用，建立了动力学光度法测定痕量亚硝酸根和硫氰酸根的新方法，测定亚硝酸根的线性范围为５－１００μｇ／Ｌ，测定硫氰酸根的线性范围为３－１２μｇ／Ｌ，用于湖水和蔬菜中的亚硝酸根量及化学试剂和尿中的硫氰酸根测定，结果满意。     

催化荧光法测定痕量亚硝酸根和硝酸根

亚硝酸盐广泛存在于土壤、天然水、食品等物质中,其易于仲胺、酰胺等反应,生成强烈致癌的亚硝胺化合物,是水污染的指标之一.亚硝酸根的测定通常采用Griess比色法,近年来又报道了极谱法和动力学法.试验发现,在稀磷酸溶液中.亚硝酸根对溴酸钾氧比罗丹明6G的反应有很强的催化作用,据此建立了测定痕量亚硝酸根的催化荧光分析方法,硝酸根可用锌粉还原至亚硝酸根进行测定.本法用于雨水中痕量亚硝酸根和硝酸根的测定,得到了满意结果.     

溴酸钾氧化酸性品红催化光度法测定亚硝酸根

研究了在强酸介质中亚硝酸根催化溴钾氧化酸性品红的褪色反应及其动力学条件，建立了高灵敏测定痕量亚硝酸根的新催化光度法。方法灵敏度为３．７×１０＾－１１ｇ／ｃｍ＾２亚硝酸态氮，线性范围为０．０６－０．４２μｇ／１０ｍＬ，用于测定唾液及硝钾中亚硝酸根。     

荧光动力学光度法同时测定硝酸根及亚硝酸根的研究

基于亚硝根对溴酸钾氧化罗丹明６Ｇ的催化及锌粉使硝酸根还原为亚硝酸根的原理，建立了同时测定亚硝酸根和硝酸根的荧光动力学法，用于饮用水、质控水样、饮料中硝酸根及亚硝酸根的测定，测定下限分别为０．０７４ｎｇＮＯ２＾－／ｍｌ和０．２５ｎｇＮＯ３＾－／ｍｌ。     

溴酸钾氧化茜素绿催化光度法测定痕量亚硝酸根

基于酸性介质溴酸钾氧化茜紊绿反应,提出了测定痕量亚硝酸根新的催化光度法.本法的Sandell灵敏度为9.4×10~(-5)μg/cm~2亚硝酸态氮,测定亚硝酸根量的线性范围为0.01～0.12μg/ml,可用于水样中亚硝酸根测定。     

溴酸钾氧化荧光素动力学荧光法测定痕量亚硝酸根

基于稀硫酸介质中,亚硝酸根催化溴酸钾氧化荧光素,建立了动力学荧光法测定痕量亚硝酸根的新方法。本方法具有高灵敏度和高选择性,测定亚硝酸根的线性范围为2～80ng/ml,可用于直接测定水样中亚硝酸根。     

催化光度法测定痕量亚硝酸根

寻找新指示物质,建立新催化动力学体系用于亚硝酸根测定能显著提高测定的灵敏度,特别是在水体及食物中痕量亚硝酸根的测定中,具有很重要的意义。本文利用亚硝酸根能灵敏地催化高碘酸钾氧化N-苯基邻氨基苯甲酸显色的反应,建立了测定痕量亚硝酸根的新方法,固定反应时间,并加入一定量的氢氧化钠溶液,以冷水流冷却,可使该催化反应中止。其反应机理为:     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.