微波辐射相转移催化合成对羟基苯甲酸杉酯的研究

以对羟基苯甲酸和氯化苄等为原料,以十六烷基溴化铵为相转移催化剂合成对羟基苯甲酸苄酯。通过实验考察了催化剂用量及物料配比等因素对酯化反应的影响。结果表明:微波辐射功率350W,辐射时间3min,n(对羟基苯甲酸)∶n(氯化苄)=1∶2,n(正十六烷基三甲基溴化铵)∶n(对羟基苯甲酸)=0.025,产率可达96.7%。     

微波辐射合成对羟基苯甲酸苄酯

以对羟基苯甲酸和氯化苄为原料,二甲基亚砜（DMSO）为溶剂,微波辐射合成对羟基苯甲酸苄酯.优化条件下：n（对羟基苯甲酸）/n（氯化苄）为1：1.70,微波辐射功率400W,反应时间4min,对羟基苯甲酸苄酯酯化收率达97.5%.     

氯化铁催化合成对羟基苯甲酸丙酯

以丙醇和对羟基苯甲酸为原料,FeCl3为催化剂,经过回流脱水酯化法合成了对羟基苯甲酸丙酯.讨论了催化酯化法中的影响因素,得到的反应最佳条件为∶n(丙醇)∶n(对羟基苯甲酸)=3∶1,n(FeCl3)∶n(对羟基苯甲酸)=0.06∶1,回流反应3h,其反应酯化率、酯的含量分别达到95%和98%以上.     

SO2-4/La2O3-TiO2-HZSM-5催化合成对羟基苯甲酸酯

将SO2-4/TiO2-HZSM-5负载镧制备了新型催化剂SO2-4/La2O3-TiO2-HZSM-5,以对羟基苯甲酸和丙醇的酯化反应为探针,考察了不同制备条件对催化剂性能的影响.结果表明:la3+浸渍浓度为0.07 mol/L,经110 ℃烘干后于500 ℃焙烧3h所得催化剂活性最好.对影响酯化反应的因素进行考察,最佳实验条件为n(醇):n(酸)=5:1,反应时间4h,催化剂用量3.0%(总物料),酯化率可达96.0%.且该催化剂具有良好的重复使用和再生能力,适宜合成对羟基苯甲酸酯.     

3-甲酰基-4-羟基苯甲酸的合成研究

以对羟基苯甲酸、氯仿为原料,以氢氧化钠溶液作为溶剂,氯化卞基三乙基铵为相转移催化剂,合成了3-甲酰基-4-羟基苯甲酸,用元素分析、IR对产物进行了表征.研究了反应物配比、溶剂浓度、反应温度、反应时间等对产物收率的影响.结果表明,当n(对羟基苯甲酸):n(氯仿)=1∶2.4,氢氧化钠水溶液的浓度35%,反应温度为65℃,反应时间为30min时,3-甲酰基-4-羟基苯甲酸的收率为55.7%.     

固体酸ZrO_2/SO_4~(2-)催化合成对羟基苯甲酸丁酯

本文研究了以固体超强酸ZrO2／SO42-为催化剂,对羟基苯甲酸和丁醇为原料合成对羟基苯甲酸丁酯,并考察了醇酸比、催化剂用量、反应时间、带水剂用量等对酯产率的影响。酯产率达87％以上。     

对羟基苯甲酸酯合成研究的新进展

综述了近年来合成对羟基苯甲酸酯研究的进展,并对其发展动态进行了展望。     

微波辐射三乙基苄基氯化铵催化合成肉桂酸苄酯

以肉桂酸钠和氯化苄为原料，三乙基苄基氯化铵作催化剂，采用微波辐射技术，在常压下直接合成肉桂酸苄酯，并对催化剂用量、微波辐射功率和辐射时间对酯产率的影响等进行了研究．研究结果表明，合成反应的最适宜的反应条件为：当n(肉桂酸钠)：n(氯化苄)一1：1．2时，三乙基苄基氯化铵的用量1．0g，微波功率300W，辐射40min，产率达81％以上．     

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。     

高效液相色谱法测定酱油和食醋中4种对羟基苯甲酸酯

建立了高效液相色谱法测定酱油和食醋中4种对羟基苯甲酸酯（对羟基苯甲酸甲酯、对羟基苯甲酸乙酯、对羟基苯甲酸异丙酯、对羟基苯甲酸丙酯）含量的方法。紫外检测器254nm处测定。结果表明,4种对羟基苯甲酸酯在0.0～50.0mg/L范围内呈现良好线性关系,各组分的检出限分别为0.1mg/kg、0.2mg/kg、0.25mg/kg、0.2mg/kg（S/N=3）,不同剂量的加标回收率为86.3%～101.6%,相对标准偏差（RSDs）为0.7%～3.1%。该方法简便、快速、灵敏,准确度和重现性较好,可作为酱油和食醋中测定多种对羟基苯甲酸酯类添加剂的有效方法。     

Western and Eastern culture differences in commercial field

The communication of people partially is the communication of cultures. Culture has a direct effect on international commercial activities in all aspects. Different conceptions about time, space, equality, law and the like, lead people to deal with things in different ways. So to know cultures of the counterpart is to facil-itate our enterprises so as to have a smooth and successful communication in commercial activity.     

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。     

风的曲线

Rosco and I wait for the fishermen to return.I sit at a wooden bench near the store at Mt.Baker Resort and watch the clouds change shape. Rosco has my belt around his neck and an eight foot tow chain hooked to a tree. Dogs must be on a leash. Ducks and rabbits are loose.     

团图为数的图中的闭团贯数

Given a graph G,a subgraph C is called a clique of G if C is a complete subgraph of G maximal under inclusion and |C|≥2. A clique-transversal set S of G is a set of vertices of G such that S meets all cliques of G. The clique-transversal number, denoted as TC (G), is the minimum cardinality of a clique-transversal set in G. The clique-graph of G, denoted as K (G), is the graph obtained by taking the cliques of G as vertices, and two vertices are adjacent if and only if the corresponding cliques in G have nonempty intersection. Let F be a class of graphs G such that F={G|K(G) is a tree}. In this paper the graphs in F having independent clique-transversal sets are shown and thus TC (G)/|G|≤1/2 for all G ∈ F.     

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?     

Social and Cultural Influence on Word Meaning

Different nations have different social cultures, and the social culture of every nation is developing with the development of the nation, language is greatly influenced by social culture, which enables language to possess national and historical characteristics. Word is the smallest, independent, meaningful linguistic unit of language. It can well reflect the national and historical characteristics. From synchronic aspect, the social and cultural influence on word meaning is mainly embodied in conceptual and associative meanings of word. The incorrespondence of word meaning is a phenomenon that exists in both conceptual and associative meanings of word among different languages. From diachronic aspect, the development of social culture causes some changes of word meaning to some extent. Therefore, social culture plays a key role in vocabulary learning and mastery of a language.     

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.