微量元素锰污染对人体的危害

介绍了微量元素锰污染的来源、毒性机理以及对人体的危害。慢性锰中毒主要表现为神经毒性、生殖毒性,锰也能引起肝脏、肺等脏器的损害。由于锰不能被生物降解,在环境中只能发生各种形态之间的转化,所以锰造成的污染消除很困难,对人体引起的影响和危害成为人们更为关注的问题。     

锰染毒对大鼠血液胆碱酯酶的影响

为了探寻锰对血液胆碱酯酶的影响，观察了染锰大鼠慢性中毒过程中血液胆碱酯酶的活性值，结果显示，大鼠血液胆碱酯酶没有呈现明显的剂量－反应关系。     

湖南省湘潭锰矿596名儿童发锰含量的调查报告

对湖南湘潭锰矿地区空气、水质、土壤和食物中标元素浓缩状态进行调查，同时对锰区１～１４岁儿童共５９６例发锰含量作了调查研究．以求得锰工业区儿童发锰含量的本底值．以便进一步探讨锰污染对人体健康的影响．检测结果：湘潭锰矿儿童发锰上限１５．８４×１０－６～１６．２４×１０－６，高于国内正常发锰上限的０．６５７倍，高于湖南医科大学附二院儿童发锰正常值的３．８６倍．锰区降尘比国家规定高４．８５倍，土壤比非锰区高９．７４倍，大米比非锰区高０．７５倍，井水、池塘水分别高于国家标准５８．６倍和１１．５倍，大气高于国家规定０．６倍．表明湘潭锰矿地区锰元素高度浓缩状况（污染状况）．儿重发锰测定结果与该地区环境中的锰含量成正相关．发锰可作为锰浓缩地区的指示器，为环保、公卫工作提供科学依据。鉴于该矿从事锰作业２５年者出现严重的锰中毒脑病．从而提示体内锰过多可引起脑功能障碍，与儿童智力精神的影响相关．正在进一步探讨高浓度的锰对正在生长发育中的儿童潜在影响和远期危害．     

人体怎样补锰

缺锰可以引起多种疾病 ,但体内锰含量过高也不利于健康 ,如含量过高会发生锰中毒 ,还会损害中枢神经。锰在人体组织中总量只有 1 2～ 2 0毫克 ,人体对锰需要量并非很高 ,成人每天 5毫克就足够了。锰元素主要靠从食物中摄取 ,食物以坚果 (如核仁、栗子、松子等 )及粗粮、干豆含锰最多 ,其次是蔬菜、干果 ,水产品、鱼肝、鸡肝等锰含量也较高。在每日膳食中 ,若荤素兼备 ,人体就可摄食 5毫克锰 ,能满足人体对锰的需要。一般来说 ,动物性食品的锰较植物性食品易于吸收。需注意的是 ,进食动物性食品时 ,不要同吃菠菜 ,不要多喝茶 ,因为茶叶中鞣酸…     

饮水引起慢性锰中毒

为查找一家两例不明原因双下肢僵硬,有下坠感症状患者的致病因素,应用电感耦合等离子体发射光谱法（ICR－AES）检测了人发和井水中锰的含量,结果表明,患者发锰高于正常值2倍以上,其饮用井水超过国家饮用标准10倍,确诊为饮水导致的慢性锰中毒。     

硫酸亚铁铵滴定法测定锰渣中的锰含量

研究了高氯酸氧化-硫酸亚铁铵滴定法测定锰渣中锰含量的主要影响因素。采用磷酸分解试样,通过控制试样质量和磷酸用量的比例,优化确定了最佳溶样温度和溶样时间,探讨了放置冷却时间对测定结果的影响程度,分析了共存离子的干扰。建立了硫酸亚铁铵滴定法测定锰渣中的锰含量的方法,方法用于对锰渣标准物质和样品进行分析,测定结果的相对标准偏差为0.21%～0.35%,准确度和精密度均能满足锰渣中锰含量的分析要求。     

锰与社会

本文简要介绍锰的存在和发现,锰在钢铁冶金中的应用,锰盐的生产和广泛用途,以及锰与人体健康的关系。     

锰试剂在有机合成中的应用

主要综述了近年来有机锰化合物及单质锰直接参与的有机反应有机合成中的应用。     

四齿锰络合物对α－蒎烯及苯乙烯的催化环氧化研究

以西佛碱锰、四苯基卟啉锰和酞菁锰络合物为催化剂，研究了在次氯酸盐体系中对α－蒎烯和苯乙烯催化环氧化的性能．比较了不同结构西佛碱锰的反应活性，发现二价锰络合物同样有催化活性，对不同催化体系进行了比较。并研究了一相催化体系中的环氧化反应。     

从软锰矿到锰同位素：锰元素的发现及其概念的发展

1771年，瑞典化学家托伯恩·伯格曼明确提出软锰矿中含有新元素的假说，并将之初步命名为manganese(锰)。1774年，瑞典矿物学家甘恩首次制取出锰单质，锰元素假说得以验证。同年，瑞典化学家舍勒对锰单质的性质进行了表征，并确认manganese(锰)一词为该元素命名，锰元素的概念正式形成。同位素化学兴起后，1923年至今共发现25种锰的同位素，锰元素被明确定义为质子数为25的所有原子的总称。锰元素的发现浓缩了19世纪初系统分析法形成以前早期分析化学的发展，其概念的演变渗透出系统分析法的形成以及同位素化学的兴起，在定性到定量的研究过程中体现了科学思想和方法的进步。     

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.     

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.     

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.     

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.     

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.     

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.     

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.