双烯合成反应浅析

对“双烯合成”的反应性、区位选择性和次级构象效应问题,从理论上进行了初步分析,主要讨论逆双烯合成反应和分子内双烯合成反应及其在合成上的应用。     

双烯合成反应浅析

对“双烯合成”的的应性、区位选择性和次级构象效应问题,从理论上进行了初步分析,主要讨论逆双烯合成反应和分子内双烯合成反应及其在合成上的应用。     

从合成子角度讨论Diels-Alder反应

本文提出合成子的活性概念,从合成子的活性定性讨论不同结构的反应物进行Diels—Alder反应的难易程度;并且通过对合成子的结合方式重点讨论Diels—Alder双烯合成和1.3偶极环加成的方向选择性问题.     

浅析高考化学试题中的双烯合成反应

从中学化学的角度介绍了双烯合成反应和相关历史背景,从双烯合成反应、化学学科思想和理念以及化学学习潜能三个维度对双烯合成反应的命题价值进行了分析,解析、点评了相关的部分高考化学试题。     

路易士酸络合催化Diels—Alder双烯加成反应探究

Diels-Alder 反应是双烯体和亲双烯体发生的1.4—环加成反应,反应速度快,应用范围广,是合成环状化合物的重要方法。双烯体包括直链和脂环二烯烃,具有易变动电子体系的芳香族化合物及含 C=O、C=N、C=C 基团的双烯体系。亲双烯体具有/n形式(Z,Z′为 X、CHO、COR、COOR、COAr、C=N、NO_2、SO_2等)。通常,双烯体分子中具有给电子基团时可加速反应;在亲双烯体中具有吸电子基团时可加速反应。     

Diels-Alder反应再认识

简单介绍了绿色介质（水、离子液体）中进行的Diels—Alder反应的特点以及反双烯合成在有机化学中的应用前景.     

α-氧代烯酮环二硫代缩酮化学——Grignard试剂与α-肉桂酰基烯酮环二硫代缩酮的区域选择性加成反应

乙基、丙基、丁基、苯基和苄基卤化镁等Grignard试剂与具有三亲电中心的肉桂酰基烯酮环二硫代缩酮类化合物2反应,生成选择性共轭加成产物3,为合成含复杂烃基的a-氧代烯酮环二硫代缩酮提供了一条新的途径.该反应体现了2中的环二硫缩酮基对反应的调控作用.     

高纯度共轭亚油酸的制备及其转化过程的表观动力学特征

共轭亚油酸是一种具有多种生理活性和潜在应用前景的脂肪酸 .研究了可用于规模化生产的高纯度共轭亚油酸的合成方法及其纯化的工艺路线和条件 .以红花油为原料 ,通过脲包纯化、共轭化制备出纯度高达 95 %的共轭亚油酸 ,总收率在 4 8%以上 .并对以葵花油为原料的亚油酸转化为共轭亚油酸的反应动力学进行了研究 ,建立了其表观动力学模型 ,为工业设计提供了依据     

苹果皮渣中苹果多酚的提取工艺优化及其抗脂质氧化活性研究

通过正交实验,对苹果渣中苹果多酚的提取工艺条件进行了优化研究,确定最佳工艺条件为:70%乙醇,料液比1:15,提取温度80℃,提取时间2.5h,提取2次,在此最优条件下,苹果多酚得率为4.69g/kg.通过抑制鱼油和葵花子油脂质氧化中过氧化值(PV)、共轭双烯值(CDH)试验表明,苹果多酚具有很强的抗氧化能力.     

Diels—Alder反应再认识

简单介绍了绿色介质（水、离子液体）中进行的Diels-Alder反应的特点以有反双烯合成在有机化学中的应用前景。     

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?     

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.     

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.     

Sister Carrie, an Adherent of Desires

Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities.     

Improvement of one-cycle controller by use of proportional integral differential controller

1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec…     

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.