碘量法测定气态氨中硫

炼油过程中产生大量的污水 ,可用污水汽提的方法降低污水中硫和氨气的含量 ,在污水中通入蒸汽或用重沸而产生的蒸汽把硫化氢和氨气提出来 ,为了进一步回收硫化氢和氨气 ,需要对氨气中硫进行测定。用乙酸锌沉淀硫离子 ,再酸化硫化锌 ,释放出的硫化氢被过量的碘氧化 ,以硫代硫酸钠标准溶液滴定剩余碘来计算试样中硫[1] ,试验表明 ,本法操作简便 ,结果准确。1　试验部分1.1　主要试剂氢氧化钠溶液 :0 .2 5ｍｏｌ·Ｌ- 1异丙醇 氨水 :10 0 + 7乙酸锌溶液 :10 0ｇ·Ｌ- 1碘溶液 :0 .0 1ｍｏｌ·Ｌ- 1,称取碘化钾 13ｇ于5 0 0ｍｌ烧杯中 ,加入蒸…     

粮食中熏蒸剂硫酰氟残留量的顶空气相色谱测定

报道了利用顶空气相色谱 -电子捕获检测法测定玉米、大米、黄豆、大麦等粮食中熏蒸剂硫酰氟残留量的方法。该法回收率(硫酰氟含量为2.0×10-6时)为95.7%～101.3% ,相对标准偏差为1.4%～3.5% ,线性范围在1×10-1～1×10-7 g/L ,粮食中硫酰氟检出限低于1.0×10-8 。该法操作简单 ,分析时间短 ,可用于粮食中残留硫酰氟含量的检测     

全氟和多氟烷基磺酸的研究 Ⅹ.在亲核取代反应中全氟烷基3-氧杂全氟烷烃磺酸酯的唯一的硫-氧键断裂

以3-氧杂多氟烷烃磺酰氟XCF_2OCF_2CF_2SO_2F为原料,合成了全氟烷基3-氧杂全氟戊烷磺酸酯XCF_2OCF_2CF_2SO_3CF_2CF_2OCF_2X(1)[X=ICF_2(1a),X=ClCF_2(1b),X=HCF_2(1c),X=Cl_2CF(1d)].1极易和多种亲核试剂反应,其中催化量的卤离子和硫氰根离子即能将1分解成相应的磺酰氟和酰氟.所有的亲核试剂和1作用时均进攻硫原子而只得到硫-氧键断裂的产物.可能的解释是由于烷醇基α碳原子上两个氟原子的屏蔽作用,使亲核试剂难于进攻碳,只能进攻硫,从而导致唯一的硫-氧键断裂.     

用氟离子选择电极方法测定四氟乙烯与全氟[3,6-二氧杂4-甲基-△~7辛基磺酰氟]共聚物的交换容量

分析四氟乙烯与全氟[3,6-二氧杂4-甲基-△~7辛基磺酰氟]共聚物(简称QF-1)的组成,一般是先将此共聚物在氢氧化钠中水解,使磺酰氟基团变为磺酸钠,然后用盐酸转型为磺酸,再用氯化钠溶液进行交换,用标准碱溶液滴定。这个方法是按离子交换膜测定交换容量(IEC)的方法求得聚合物的当量值,从而得知其组成,但步骤较多。为了减少滴定的误差,聚合物用量也较多,一般需在0.5克以上。考虑到QFeel中除磺酞氟以外的氟原子对碱均很稳定。在水解时只发生下列反应.R,一50:F ZNaOH一)一一今R,一50必Na NaF H:O因而氟离子和磺酸基是等当量的.测定该聚合物碱水解液中的氟离子量,即可知交换当量.粉状树脂不需加工成膜,即可作为试样进行测定,操作简便。又由于氟离子选择电极灵敏度很高,     

在 Pt/TiO2上光催化降解污水中的对氟苯甲酸

在Pt/TiO2存在下,研究了光催化降解对氟苯甲酸的反应.考察了反应时间、溶液初始pH值以及污染物初始浓度对光催化反应的影响.结果表明,溶液的紫外吸光度值随反应时间不断下降;反应7 h时,溶液的TOC去除率达23.2%;反应0.5～2 h内,氟离子平均生成速率为3.53×10-5mol.L-1.h-1;在反应3～7 h内,氟离子平均生成速率为6.22×10-5mol.L-1.h-1.在溶液初始pH值=3.34～3.72时,氟离子生成速率最大,在碱性范围内,氟离子的生成速率为零.当C0(p-fluorobenzoic acid)<1.80×10-3mol.L-1时,光催化降解生成氟离子的速率随着对氟苯甲酸浓度的增大而增大;当C0(p-fluorobenzoic acid)>2.00×10-3mol.L-1时,光催化降解生成氟离子的速率不再随污染物浓度的变化而发生变化.探讨了可能的反应机理.     

用碘离子选择性电极测定砷(Ⅲ)

砷是自然界中普遍存在而且对人体有毒的化学元素之一 ,目前分析砷的方法很多[1,2 ] ,本文用碘离子选择性电极间接测定砷 (Ⅲ )的含量 ,方法操作简单 ,结果可靠 ,检出限可达到 6.2 5× 1 0 -7ｍｏｌ·Ｌ-1。1　试验部分1 .1　主要仪器与试剂ｐＸＳ 2 1 5离子活度计(上海精科雷磁公司 )79 1型磁力加热搅拌器碘离子选择性电极 (江苏电分析仪器厂 )离子强度调节剂 :0 .5ｍｏｌ·Ｌ-1ＫＮＯ3 +0 1ｍｏｌ·Ｌ-1氯乙酸水为二次蒸馏水1 .2　试验方法取 5 0ｍｌ容量瓶若干个 ,分别加入 0 .5ｍｏｌ·Ｌ-1ＫＮＯ3 溶液 5ｍｌ,0 .1ｍｏｌ·Ｌ-1氯乙酸 2…     

硝酸活化高灵敏度离子选择性电极法测定氟

先在0．5 mol·L-1硝酸介质中活化氟离子选择性电极,再在含硝酸的总离子强度调节混合液(TISAM)中测定氟,线性范围为1×10-7～1×10-2mol·L-1,检出限为1．9μg·L-1。该方法应用于绿茶饮料、水、牛奶中痕量氟的测定,结果的RSD小于4．8％,回收率在96．1％至100．2％之间,对氟离子选择性电极在硝酸介质中的活化机理作了阐述。     

离子选择性电极非线性测定水中氟离子的含量

利用氟离子选择性电极测定系列氟离子标准溶液的电极电位(vs.SCE),用测得的电极电位值与氟离子标准溶液的浓度数据进行非线性工作曲线拟舍,可准确测定1×10~(-6)～1×10~(-5)moL/L氟离子溶液的浓度。该法易于实现氟离子溶液的自动连续监测,适于氟离子溶液浓度的在线测量。     

离子色谱法同时分析中药丹参中碱金属和碱土金属

用离子色谱法同时分析中药丹参中碱金属和碱土金属 ,结果表明 ,丹参中常见离子Li+ 、Na+ 、NH+4、K+ 、Mg2 + 、Ca2 + 含量比例各有不同。各离子的检出限为 0 .0 1～ 0 .0 3mg·L-1,线性范围分别为 0 .1～ 10 .0mg·L-1(Li+ 、NH+4)和 0 .2～ 5 0 .0mg·L-1(Na+ 、K+ 、Mg2 + 、Ca2 + )     

铜(Ⅰ)-硫氰酸盐-丁基罗丹明B体系高灵敏度显色反应研究及其应用

铜 (Ⅱ )被还原后 ,可与SCN- 、丁基罗丹明B形成三元配合物 ,该化合物在 0 .0 4mol·L- 1硫酸介质及 0 .4g·L- 1乳化剂OP存在条件下 ,可形成 1∶3∶2的离子缔合物。其最大吸收峰为6 0 5nm ,摩尔吸光系数为 2 .5 8× 10 5L·mol- 1·cm- 1,检测范围为 0～ 3.5 0 μg/2 5ml。检出限为 0 .30 μg/2 5ml。该方法用于粮食及人发等试样中铜的测定 ,结果满意     

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%.     

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.     

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.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

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.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

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.