突破纤维素水解的技术难点

纤维素水解实验比较难做的主要因素有 2个 ;一是水解时间过长 ,二是水解液的碱化终点不好判断。笔者经过反复研究 ,发现了一种仅用 4ｍｉｎ就足以完成这一包括水解—中和—检测 3个环节的实验方法。现提供给大家 ,供同行们参考。1　实验方法(1)水解液的制备①取少许药棉 (即脱脂棉 )用水润湿 ,挤出水分并捻成一团后松开约黄豆粒大小 ,装入试管。②向试管中注入 2ｍＬ浓Ｈ2 ＳＯ4 并用力振荡试管使液体呈无色粘稠状。把试管放进沸水中浴热(预先备好沸水浴装置 )。③大约 1ｍｉｎ ,液体表层微显亮棕色 (表层以下的液体仍呈无色粘稠状 )。此时…     

蔗糖、淀粉、纤维素水解的演示实验

新编全日制十年制高中课本第二册第六章中的演示实验[实验6-2]、[实验6-3]、[实验6-4]、[实验6-9]等四个实验,从教材编排来看,主要通过演示实验达到突出糖类的水解及酶的作用,所以做好这四个演示实验对讲清糖的水解和酶的特性起很重要作用。     

元素硫水解反应机理研究

元素硫沉积加剧油气田管材和设备的腐蚀,为探寻元素硫水解腐蚀机理,对元素硫水解后溶液的p H值及S2-、SO2-4含量进行了测定,研究实验温度、反应时间及硫含量对硫水解反应的影响。结果表明:实验温度对硫的水解起决定作用,只有当温度超过某一临界值(60℃),水解反应才能发生;硫的水解存在诱导期(2h),其后,硫的水解反应程度随反应时间的延长而增强;硫含量同样能够影响硫的水解。基于实验结果,建立了元素硫水解模型,讨论了元素硫水解机理,水解过程中所形成的"氢离子载体"能自催化元素硫的水解。     

手持技术支持下的乙酸乙酯水解实验探究*

乙酸乙酯的水解实验是现行高中有机化学教学内容中的重要实验,教材中提出通过观察酯层消失的时间差异来判断水解速率的差别,在实际操作过程中实验效果并不理想。借助手持技术分别探究了乙酸乙酯在中性、酸性、碱性、不同温度条件下的水解速率情况,并借助相关知识理论分析了乙酸乙酯在酸性和碱性条件下水解速率的差异,旨在帮助教师和学生深度理解乙酸乙酯发生水解的条件及规律。     

油脂与醣类作化学上加工制造的学校实验(二)——淀粉加工制造

淀粉的加工制造淀粉水解实验使学生知道多醣类与已经学过的水溶性醣类的关系;并以科学原理使学生知道食品工业的重要部门和在人体组织中发生的现象(如在唾液酵素作用下)。自淀粉制造葡萄糖是一个很有趣的实验,但是费时颇入,如果把整个操作分成几个部分,这一实验是可放在课上进行的。     

“温度对盐类水解影响”的实验探讨与设计

在对实验中选取的FeCl3、指示剂和pH传感器存在的问题进行理论和实验说明的基础上,明确应选择仅存在单纯水解平衡的溶液体系,且将水解平衡自身现象的变化应作为实验的判断依据。进而从生成气体、沉淀和溶液颜色变化3个角度对反应物的选取进行了理论分析,并选取常用的盐类代表物进行实验验证,提出Fe(NO3)3、Fe2(SO4)3、CuSO4及酸化后的SnCl2溶液适合作为高中探究"温度对盐类水解影响"的反应物。     

油脂与醣类作化学上加工制造的学校实验(三)——纤维素水解

纤维素水解(主要是木材水解)制造酒精及一系列其他产品在工业上逐年扩大。(5)纤维素水解为葡萄糖及葡萄糖醱酵为酒精的实验阐明了水解工业的整本化学过程意义,而图,表,模型的演示指出关于这些过程在工厂条件下实行的概念。木材糖化的工业方法,是用木材与稀硫酸(0.5％)加热进行。要使水解进行得相当快需要较高温度;因之反应物在加压下加热。在180°时水解带率对工业上说是满意的。在学校中不易使实验在加压下进行,因之需要浓酸来增加水解速率。     

淀粉、纤维素水解实验的改进

现行高级中学课本化学(选修)第三册多糖的教学内容中,安排了淀粉和纤维素水解的两个演示实验。做好这两个实验,对引导学生学好淀粉和纤维素的重要性质很有必要。     

镁和氯化铵溶液反应的实验研究

在学习了“盐类水解”之后,许多学生认为镁能够与氯化铵溶液剧烈反应的原因是:氯化铵水解呈酸性,镁与水解产生的H+反应生成氢气,反应的离子方程式为NH4++H2O NH3·H2O+H+,Mg+2H+Mg2++H2↑;这种观点也为许多教师所认同,在有些教学参考资料上也有类似的解释[1],但笔者认为这一解释不符合反应事实,为此笔者进行了以下5个实验。实验1:在盛有3.0mL1.0mol/LNH4Cl溶液的试管中加入0.20g镁粉观察到有大量气泡产生,一段时间后溶液中有白色沉淀形成。实验2:在盛有3.0mL1.0mol/LCH3COONH4溶液的试管中加入0.20g镁粉,观察到有大量气泡生成,…     

锌跟硫酸铜溶液反应的研究

锌跟硫酸铜溶液反应．在锌粒表面生成一层黑色粉状物。通过实验证实,黑色粉状物是铜、氧化铜和锌粉的混合物。氧化铜的生成,是硫酸铜水解生成氢氧化铜,氢氧化铜分解生成氧化铜。锌跟硫酸铜溶液反应,要观察到紫红色铜的生成,就要抑制水解,把硫酸铜配成饱和溶液。     

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。