甲苯合成苯甲酸实验的改进

本文探讨在相转移催化剂催化下用高锰酸钾氧化甲苯合成苯甲酸。通过实验对催化剂种类，用量，原料摩尔比，水用量，反应时间进行了研究，最后找出最佳反应条件为：TBAB为催化剂，用量为5％（摩尔百分比），甲苯／高锰酸钾／水：1：2．2：260，反应时间为2h，收率可达80．50％。     

硫酸氢钠催化合成癸二酸二丁酯

研究了以硫酸氢钠为催化剂，癸二酸和正丁醇为原料合成癸二酸二丁酯。并考察了影响反应的因素．结果表明，醇酸摩尔比为3：1，催化剂用量为0．2g(癸二酸为0．05mol的情况下)，带水剂甲苯为5mL，反应温度为110。140℃，反应时间为1．0h是最适宜的反应条件，酯化率这98．6％．     

四氯化锡催化合成肉桂酸乙酯

四氯化锡能够代替硫酸用作酯化催化剂，在五水四氯化锡催化下合成了肉桂酸已酯，考察了n(肉桂酸)、n(肉桂酸)、反应时间、n(四氯化锡)等因素对反应的影响，结果表明：当n(肉桂酸)：n(乙醇)：n(四氯化锡)＝1：7．5：0．22，回流时间3h，酯收率达91．4％。同时用折射率、元素分析和红外光谱进行了表征，产品完全合格。     

为什么会多于理论量

例 由实验测知，加热3．5g高锰酸钾晶体到220℃，分解放出的氧气多于按下式计算的理论量．按下式计算的理论量为0．354g氧气，换算成标准状况下的体积为248mL，而实际测得的氧气为308mL(标准状况下)，超出308-248=60(mL)．     

氯化锡催化合成丁酸戊酯初探

本文使用氯化锡作为丁酸和戊醇的酯化催化剂。通过L9(3^4)正交实验探讨了回流时间、反应温度、催化剂与酸物质的量比、酸与醇物质的量比等因素对产品丁酸戊酯产率的影响。当n(催化剂)：n(酸)=1：150，n(酸)：n(醇)=1：1、4，在155—160℃下回流搅拌反应2．0h，不使用任何带水剂时；产品丁酸戊酯的产率为83．4％。     

高锰酸钾氧化甲苯的实验方法

甲苯的化学性质比苯活泼,能被高锰酸钾氧化,使高锰酸钾溶液褪色。因此常常利用这一性质和现象来鉴别苯和苯的同系物。但在课堂演示实验和学生实验时,往往出现甲苯不能使高锰酸钾溶液褪色或者苯也能使高锰酸钾褪色的“异常”现象。计对这一情况,我们进行了认真的分析,多次实验,并进行了如下改进。 1 适当的加热 由于甲苯不易溶于水,当甲苯与高锰酸钾溶液混合时,很快分成两层,即甲苯层和水层,不能使高锰酸钾与甲苯充分接触,很难发生反     

硅钨酸掺杂聚苯胺催化剂催化合成苹果酯

自制了硅钨酸(H4SiW12O40)掺杂聚苯胺(PAn)催化剂H4SiW12O40／PAn．以乙酰乙酸乙酯和乙二醇为原料合成苹果酯．较系统地研究了原料摩尔比、催化剂用量、反应时间诸因素对产品收率的影响．实验表明：最佳反应条件为n(乙酰乙酸乙酯)：n(乙二醇)=1：1．5。催化剂用量为反应物料总质量的0．5％。环己烷为带水剂，反应时间1．0h．上述条件下．苹果酯的收率为71．5％．     

活性白土负载磷钨酸催化合成乙二醇单乙醚醋酸酯

以醋酸和乙二醇单乙醚为原料，活性白土负载磷钨酸作为催化剂，合成了乙二醇单乙醚醋酸酯。考察了不同反应条件对产率的影响。最佳反应条件为：磷钨酸固载量35％、催化剂焙烧温度180℃、催化剂用量为醇醚质量的5％、酸醇摩尔比为1．2：1、带水剂甲苯用量为反应物质量的15％和反应时间为1．5h，产率可达到99％。     

高锰酸钾法制备对硝基苯甲酸

以高锰酸钾和对硝基甲苯为原料合成了对硝基苯甲酸．考察了制备对硝基苯甲酸时反应体系的酸碱性、稀硫酸浓度、反应物配比、反应温度、反应时间对产物对硝基苯甲酸收率的影响．结果表明：酸性条件,稀硫酸浓度1．5mol／L、反应物配比5：1、反应温度60℃、反应时间2h,为最适宜的反应条件．     

水杨酸戊酯的催化合成

以对甲苯磺酸为催化剂，通过水杨酸和戊醇酯化反应合成水杨酸戊酯、研究了催化剂用量、酸醇物质的量比以及反应时间等因素对水杨酸酯化率的影响．实验结果表明，对甲苯磺酸是合成水杨酸戊酯的良好催化剂．在酸醇物质的量比为1：1．6，催化剂用量为6％，带水剂甲苯10mL，反应时间5h，反应温度120～140℃的条件下，水杨酸的酯化率可达94．1％．     

汉字倒说

汉字的六书,《说文》对“转注”一类,语焉不详。后世学者提及转注,也仅限于许慎所举出的例字。《汉字例说》一文,作者从转注的角度综合考虑,对部分现代常用字作了分析,跟传统的解释有所不同。希望能抛砖引玉,互相切磋,以推进学术研究。     

卡思卡特城堡

It is worthy of noting that, whilst Crookston Castle witnessed the earlier and happier portion of Mary's variegated life,     

不同的吃喝玩乐

一、吃和喝吃苹果 eat an apple, 吃药 take medicine,吃糖 have some sweets,吃饭 have one's meals,吃馆子 dine out,吃惊 be surprised/     

漏洞百出的教育

Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help?     

钱生钱!

我们绝大部分人都同意一件事情——我们喜欢金钱。但是你对金钱的喜欢之情足够到让你创立一份事业么?.财富通常被人忽视,主要在于人们不能真正了     

Inequalities for inscribed simplexes

The problem on the geometrc inequalities involving an n-dimensional simplex and its inscribed simplex is studied. Aninequality is established, which reveals that the difference between the squared circumradius of the n-dimensional simplex andthe squared distance between its circumcenter and barycenter times the squared circumradius of its inscribed simplex is not lessthan the 2(n-1)th power of n times its squared inradius, and is equal to when the simplex is regular and its inscribed siplex is atangent point one. Deduction from this inequality reaches a generalization of n-dimensional Euler inequality indicating that thecircumradius of the simplex is not less than the n-fold inradius. Another inequality is derived to present the relationship betweenthe circumradius of the n-dimensional simplex and the circumradius and inradius of its pedal simplex.     

只要努力,不要后悔

There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love.     

浅谈移民问题

Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject.     

微薄的薪水,高尚的情操

现在,我们可以没有面包,没有钱,没有房子,没有车子……但我们唯独不能丢失的是高尚的情操,笃定的信念,还有,满满的希望!     

Virtual reality approach for 3D large model browsing on web site

Using virtual reality for interactive design gives a designer an intuitive vision of a design and allows the designer to achieve a viable, optimal solution in a timely manner. The article discusses the process of making the Virtual Reality System of the Humble Administrator＇s Garden. Translating building data to the Virtual Reality Modeling Language （VRML） is by far unsatisfactory. This creates a challenge for computer designers to do optimization to meet requirements. Five different approaches to optimize models have been presented in this paper. The other methods are to optimize VRML and to reduce the file size. This is done by keeping polygon counts to a minimum and by applying such techniques as object culling and level-ofdetail switching.