逆向配平法

逆向配平法是从给生成物配系数开始配平氧化还原反应方程式的一种方法。此方法根据氧化还原反应中氧化数的增减总数相等的原则,配平氧化还原反应方程式的步骤如下。(1)写出反应式,标出发生氧化和还原的元素原子在反应前后的氧化数,例如:Cu2S 1-2 HN 5O3Cu 2(NO3)2 H2S 6O4 N 2O H2O(2)分别确定氧化剂、还原产物、还原剂和氧化产物的代表,通常它们的代表是化学式中标明氧化数的原子和标明氧化数的同种原子部分(如Cu 12S-2中的Cu 12)。例如在上面反应式中,氧化剂HN 5O3的代表是N 5,还原产物N 2O的代表是N 2,还原剂Cu 12S-2的代表是…     

有机化合物的氧化数

有机化合物的氧化数吴阿富（浙江医科大学药学系，杭州３１０００６）无机化合物、有机化合物的氧化还原反应在化学反应中占有重要地位￣［１］。但它们之间的反应机理略有不同：无机化合物的氧化还原反应有明确的电子转移，氧化剂获得的电子数等于还原剂失去的电子数；而...     

计算氧化还原当量的简捷方法——差示氧化数法

氧化还原反应是一种电子得失（或转移）反应,其氧化还原当量可由下式求得：氧化还原当量=分子量/总电子得失（或转移）数对无机物来说,得失电子数极易看出,计算当然简单。     

对立统一规律在氧化还原反应中的体现

氧化还原反应是化学反应中一个十分重要的内容。运用辩证唯物主义观点,正确理解和掌握氧化还原反应,对生产实践很有好处。氧化还原反应体现了事物对立统一的法则氧化还原反应,就是体系内有关各种物质的元素原子参与电子得失过程所引起的化学变化。得电子的过程叫还原,失电子的过程叫氧化。在氧化还原反应中,得电子与失电子是一对矛盾。没有失电子,就无所谓得电子;一物质失去电子的同时,必有另一物质获得电子。假如没有氧化剂存在,还原剂就不会无的放矢地把电子释放出来;没有还原剂放出电子,氧化剂就不可能获得电子。在 S~(2-)离子变成 S 的反应中失去了两个电子,但这仅仅是反应的一半,必须有另一物质获得     

《电子得失守恒法》解题探讨

在涉及氧化还原反应的化学计算题中,应用电子得失守恒关系,可快速简捷地解答题目.     

无机氧化还原反应的专题复习

氧化还原反应知识是一条贯穿高中化学始终的“动脉” ,其重要性不言而喻 ,有必要进行专题复习。1　概念体系在氧化还原反应中 ,氧化剂表现氧化性、还原剂表现还原性。2　反应类型为了研究的方便 ,可以把氧化还原反应按不同的标准分类 ,如 :3　反应规律3.1　表现性质规律 :元素处于最高价时只具有氧化性、处于最低价时只具有还原性、处于中间价态时既具有氧化性又具有还原性。3.2　性质强弱规律 :在“氧化剂 +还原剂→还原产物 +氧化产物”中 ,氧化性 :氧化剂 >氧化产物 ;还原性 :还原剂 >还原产物。3.3　正易逆难规律 :若“氧化剂 +e- →还…     

梳理知识提高应用能力——小议"氧化还原反应"的专题复习

氧化还原反应是极为重要的化学反应类型,也是历年高考的重要考点。对此考试大纲明确提出:“理解氧化还原反应,了解氧化剂和还原剂等概念;掌握重要的氧化剂和还原剂之间的常见反应;能判断氧化还原反应中电子转移的方向和数目,并能配平反应的化学方程式”等5项考点。另一方面新课     

关于氧化还原平衡处理方法的讨论

氧化还原滴定是分析化学教学的基本内容之一。但氧化还原滴定的理论处理尚不如酸碱与络合滴定理论处理那样完善,有的问题还处于研讨之中。本文拟对氧化还原平衡处理方法中出现的两个新概念——电子活度与半反应平衡常数谈一谈看法,并对氧化还原平衡的图解法提出作者的建议。     

氧化还原滴定计算新思路

提出一种计算氧化还原滴定的新思路.该思路根据电子守恒原则,提出了电子条件式的概念和书写方法.利用该法可一步写出氧化还原滴定计量关系式,且所得计算式容易从化学的角度来理解.     

硝基苯还原反应的机理探讨

硝基苯在不同的还原剂及不同的介质中可以被还原成亚硝基苯、苯胲、偶氮苯、氧化偶氮苯、氢化偶氮苯等不同产物。这一性质深刻揭示了还原剂的还原能力除了与本身的性质有关之外,还与反应介质密切相关。由于这些还原产物结构复杂,相应反应的机理在国内外常见经典有机化学教科书中鲜有描述,给初学者的学习理解造成了困难。本文从氧化还原反应中电子守恒原理出发,探讨了这一组还原反应的可能机理,并导出了完整的化学反应方程式。     

非那雄胺合成工艺改进

非那雄胺能抑制5α-还原酶的活性,明显降低二氢睾酮水平,是一种治疗良性前列腺增生的有效药品。该合成工艺以甾烯酮酸为原料,将其与氯化亚砜反应,无须分离即与叔丁胺反应得17β-酰胺化合物,再氧化开环,环合,氢化,脱氢合成了非那雄胺。经元素分析、IR、1HNMR、13CNMR、MS分析表征了其结构。该法无须使用昂贵的2,2-二吡啶二硫化物和剧毒药品苯亚硒酸酐,且以乙酸铵代替氨气,降低了对设备的要求和腐蚀,更适用于工业生产。     

Dichroism of absorption and polarization of phosphorescence of molecules of the closed form of nitrobenzospirothiopyran

The spectral-polarization characteristics of absorption and phosphorescence of molecules of the initial form of nitro-substituted indolinospirobenzothiopyran were studied in oriented polyethylene films and in solutions with different polarity. An oscillator model of the electron transitions responsible for the formation of absorption and luminescence spectra was suggested. It was established that the principal differences in the spectral and photophysical properties of the compound studied and its oxygen-containing analog are associated with the fact that the electronegativity of the S atom is lower than that of the O atom. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1143–1146, June, 1997.     

Acid hydrolysis of carboxymethylcellulose of low degree of substitution

Cotton cellulose was swollen in a sodium hydroxide solution and carboxymethylated by a two-bath method for different periods of time for each process. The kinetics of acid hydrolysis and the crystallinity of the swollen and carboxymethylated samples were measured. The proportion of broken bonds, rate constants for hydrolysis, and permeability of cellulose to hydrolyzing agents were calculated. The susceptibility of glycosidic linkages to acid hydrolysis was improved by carboxymethylation more than by swelling in alkali. The increased accessibility of carboxymethylcellulose to acid was regarded as a consequence of increased intra-and intercrystalline swelling and of the glycosidic bonds' weakness caused by the electron-attracting carboxymethyl group on the C-6 position.     

Estimation of Kinetic Parameters of Thermal Oxidation of Ilmenite

The aim of the presented work was the investigation of thermal oxidation of ilmenite in static air atmosphere. The investigations were carried out by use of a derivatograph (MOM, Hungary). The changes of crystallographic structure of investigated samples were identified by X-ray diffractometry on Philips PW-1710 diffractometer. In temperature above 500°C appears structure of hematite Fe₂O₃. On the basis of the thermogravimetric measurements, the contracting area and contracting volume models were found as the best fitting experimental data. This revised version was published online in August 2006 with corrections to the Cover Date.     

Mechanism of action of base-catalyzed oxygenation of phenol derivatives

Cyclopropyl derivative of 2,6-di-tert-butylphenol is synthesized as a probe to investigate the mechanism of base-catalyzed autooxidation of phenol derivatives. Our study indicates that one electron reduction of molecular oxygen from phenolate gives phenoxyl radical 3, a key intermediate of autooxidation. The coupling of phenoxyl radical and superoxide radical gives peroxylate anion 4 and produces the final epoxy alcohol adduct 6.     

氯氧化镁生成热的研究

用氧化镁氯化镁水溶液制备了8水合氯氧化镁[nMg(OH)2·MgCl2·8H2O], 并测定了其在盐酸中的溶解热, 实验结果表明, 氯氧化镁溶解热与n值呈线性关系, 根据溶解热求出5Mg(OH)2·MgCl2·8H2O和3Mg(OH)2·MgCl2·8H2O的生成热分别为-7727.1和5888.1kJ·mol^1^-。     

化学计量中不确定度评定研究进展

测量不确定度是表征合理地赋予被测量之值的分散性的参数。本文针对化学计量不确定度评定基础模型仅适用于线性模型、概率分布为正态分布或缩放位移t分布等局限,介绍了近年来不确定度评定的研究热点:蒙特卡罗方法(Monte Carlo Method,MCM),不确定度评定的来源、评定概念、评估方法及其发展过程,扩大了测量不确定度评定与表示的适用范围。     

微量钙的测定方法研究进展

介绍了1995-2006年期间测定微量和痕量钙的方法,如电感耦合等离子体-原子发射光谱法、原子吸收光谱法以及离子色谱法等的工作原理和特点,并说明了其测定微量钙的应用领域。并对微量钙的测定技术进行了展望(引用文献55篇)。     

Stages of thermal decomposition of sodium oxo-salts of sulphur

Thermal behaviour of sodium oxo-salts of sulphur: Na₂SO₄, Na₂S₂O₇, Na₂S₂O₆, Na₂SO₃, Na₂S₂O₅, Na₂S₂O₄, Na₂S₂O₃, Na₂S₃O₆ and of sulphides Na₂S and Na₂S₂ was studied on heating up to 1000°C. The experiments were performed with anhydrous compounds obtained from commercial products by recrystallisation and dehydration. The stage mechanisms of decomposition of anionic sub-lattices of the salts have been proposed basing on the Górski’s morphological classification of simple species. The thermal stability and the stage decomposition mechanisms were correlated with the structure and the potential chemical properties of the salt anions. The thermal decomposition processes were studied by means of thermal analysis, and the decomposition products were identified by means of X-ray phase analysis.     

Synthesis of phenolic components of Grains of Paradise

Two vanilloids, (5E)-8-(4-hydroxy-3-methoxyphenyl)oct-5-en-4-one (1) and 4-[3-hydroxydecyl]-2-methoxyphenol (2), isolated from the dried seeds of Grains of Paradise (Aframomum melegueta), were synthesized; the latter compound was made as the S-enantiomer and the material derived from the seeds was found to be a 1:1.7 mixture of the R and S isomers. The synthetic route used should allow the preparation of analogs having extended alkyl chains and consequently different lipophilicity, and 3, a homolog of 2, was also prepared.