烃氯代物种数判断的解题策略

判断烃氯代物数目的问题在高中有机化学和高考试题中屡见不鲜,解答这类习题,学生往往感到棘手。这类问题有无规律可循?下面我们进行分类研究。     

小议命题思路的改革

学习化学离不开解化学习题,但历来主要是围绕本学科的基本原理、基本概念或重要知识与技术命题。即使是化学竞赛的命题也大致如此。这类习题固然有助于学生巩固与深入学习课程的重要内容,包括有关知识点之间的综合与联系,但是一般难以真正贴近学生的生活和培养他们综合运用从各门课程中所学到的知识,不能不认为是这类习题的重要缺陷之一。     

结合生产内容的化学习题

在中学里通过学生解答有关生产内容的化学习题,可以使他们了解化学生产的概念,特别是了解如何充分利用原料,原料的综合利用和设备的生产率;并且能够使学生易于对化学工厂中所采用的设备有一立体的概念。下面列举一些与盐酸和硫酸生产有关的典型习题。演算斜体字的习题必须有一些理论知识,这些知识是学生在九、十年级所学到的。在应用这些习题时,教师可以根据学生的知识水平以及考虑到演算时所需的时间自行处     

谈谈构建化学教师的素材库

化学素材库中的素材,包括各种资料、习题、图表、照片、动画、声像等。在现代教学环境下,教师书写教案、演讲稿,编制习题、试卷时,离不开各种素材。本文较详细地论述了化学素材库中的素材类型及构建素材库的常用方法。     

例谈化学习题教学与探究实验的整合

习题教学是化学教学的重要组成部分。但现今的习题教学存在着量大重复、教师讲评方法刻板、学生解决方式单一等缺点。有效整合习题教学与探究实验,可以提高习题教学的效率,更好促进学生发展。     

谈提高化学习题教学的效益

化学习题教学是化学教学内容的重要构成之一,是贯穿整个教学过程、落实学生能力培养的一条重要脉络,也是师生双向交流最广泛的教学活动之一。新颁布的《全日制中学化学教学大纲》,明确提出了“加强化学习题教学”的课题。当前,化学习题教学耗时多,效益不高。落实大纲的要求,加强化学习题教学,减轻负担,提高效益,是十分紧迫的任务。1. 应当重新认识化学习题教学的作用,扭转以题海应付考试的不良倾向。     

创新性化学习题的设计

当前化学教学中,习题是培养学生创新意识和创新能力的主要手段。如何根据课程改革和高考改革的要求,编制高质量的创新性试题,是广大化学教师必须认真面对的重大研究课题。本文拟就创新性化学习题的编制做一些探讨。     

化学解题中的知识分析及其教学启示

以“书写电解池的电极反应式”的习题为例,对解题中所运用的化学知识进行具体分析。在解题的过程中,需要运用到解题步骤这一技能性知识,同时每一个子步骤都要运用到相应的化学事实性知识或理论性知识。其中任一知识的缺失都会导致解题的失败。可见,知识对于化学解题具有极其重要的意义,为了使学生更好地掌握化学知识,在化学教学中应注重知识的教学及其科学化。     

发挥习题课的作用 培养学生能力

说起习题,容易使人联想到“题海战术”,其实谁都知道“题海战术”要不得,但化学教学又绝对离不开化学习题,如何不搞“题海战术”而又能充分发挥化学习题在化学教学中的重要作用很值得我们化学教师去研究。我们在摒弃“题海战术”的同时,要以精心设计的习题课为引导,使学生通过做化学习题更全面地培养能力。     

写给青年朋友们

因为这次化学竞赛和各种考试不同,所以这份资料也就和各种习题解答不同。我们希望大家从中得到的不只是答案,更重要的是了解怎样思考和解决问题,怎样学好化学。     

利用手持技术改进测定乙醇分子结构实验

利用压强传感器代替排水集气法,改进测定乙醇分子结构实验的仪器装置,并探索最佳反应条件。另外,设计两个空白实验,结合压强变化曲线对实验误差进行相关讨论。     

光谱仪测试范围的扩展

由于石化行业的生产需要，其材质的使用具有多样性和广泛性，经常会出现顾客委托的测试样品的一个或几个元素跨越光谱仪现有测试程序测量范围的情况。本法通过对光谱仪测试原理的认识，根据光谱仪的测试能力及标样的采集，实现了一个或几个元素测量范围的扩展，并对其测量的影响因素进行了研究。     

Influence of viscosity of medium on processes of oxygen quenching of excited states of mesoporphyrin

The oxygen quenching rate constants for singlet and triplet excited states of the dimethyl ester of mesoporphyrin IX increase with decreasing viscosity of the medium and reach a maximum at a viscosity of approximately 0.4 mPa·sec, after which the rate constants begin to decrease. The drop in rate constant with increasing fluidity of the medium may be related to a nonequilibrium character of the elementary act in the interaction of the reactants in the solvent cage. In viscous media such as isopropyl alcohol, isobutyl alcohol, and isoamyl alcohol, the reaction radius is greater than the sum of the radii of the reacting particles. The long-range character of these processes is due to the relatively weak dependence of the quenching probability on distance.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 2, pp. 161–167, March–April, 1989.     

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.     

Determination of heats of detonation and influence of components of composite explosives on heats of detonation of high explosives

The heats of detonation of 20 simple high explosives and explosive mixtures were determined by means of an adiabatic detonation calorimeter designed by the authors. The results indicated that the performance of the instrument was reliable and the experimental data were very accurate. For explosive mixtures, there was a linear accumulative relationship between the heats of detonation of the explosive mixture and its components. Accordingly, the heats of detonation of explosive mixtures could be calculated directly from the heats of detonation of simple explosives and the characteristic heats of other components. The experiments showed that the gold or brass shell of the cylindrical charge could be substituted by a thick-walled porcelain shell, which had the advantage of cheapness.

     

物质分配系数的测定实验改进

实验教学目的是从解决实际问题出发,以实验技术训练和实验设计思想培养为目标。介绍了将单一的物质分配系数测定实验改进为综合实验,提高了实验效果及实验资源利用率。     

Neutral diterpenoids of oleoresins of five species of conifers of Transcarpathia

The compositions of the neutral diterpenoids of the oleoresins of five species of conifers growing in the Transcarpathia have been studied. It has been found that the oleoresins ofAbies alba M.,Larix decidua M., andPicea excelsa L. contain more than 50% of neutral diterpenoids. The group and qualitative compositions of the oxygen-containing diterpenoids have been determined. In the oleoresins ofAbies alba,Picea excelsa, andPicea abies tertiary alcohols — cis-abienol and isocembrol — predominate, while inLarix decidua the main component is the hydroxy ester larixyl acetate. Primary alcohols related to the resin acids have been found in all the oleoresins investigated. Features of the distribution of diterpenoids according to the species of conifers have been revealed. The results obtained are necessary for the chemotaxonomy of conifers of the family Pinceae.Novosibirsk Institute of Organic Chemistry, Siberian Branch, Academy of Sciences of the USSR. Translated from Khimiya Prirodynkh Soedinenii, No. 6, pp. 812–816, November–December, 1988.     

Calculation of enthalpies of hydrogenation of hydrocarbons

Sets of hydrogen molecule equivalents have been developed which permit the calculation of hydrogenation of different types of carbon-carbon bonds from ab initio total energies (3-21G and 6-31G* basis sets, and, to a more limited extent, for MP2/6-31G* data) of reactants and products. The calculated enthalpies of hydrogenation are in good agreement with experiment for unstrained molecules, with average errors on the order of 2 kcal/mol. The 6-31G* equivalents allow the enthalpies for strained molecules to be calculated accurately, but the 3-21G equivalents do not. The equivalents for both basis sets have been tested by calculating the enthalpies of hydrogenation of carbon-carbon bonds in nitrogen- and oxygen-containing organic molecules, free radicals, and classical carbocations. The results are in good agreement with experiment in most cases.     

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。