共查询到20条相似文献，搜索用时 62 毫秒
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以叶绿素-α重要衍生物脱镁叶绿酸-α甲酯1为研究对象,与溴化氢反应生成亲电加成产物卟吩2,然后在碱性条件下与四氧化锇作用,其7-8位的碳碳双键发生氧化反应,生成邻位二醇卟吩3.讨论了卟吩环系的共轭体系和芳香性质,以及与化学反应活性的联系. 相似文献
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以脱镁叶绿酸-α甲酯为起始原料,利用E-环β-酮酯的化学反应活性进行化学结构修饰,通过空气氧化反应和相应的重排反应,分离出红紫素-18甲酯和卟吩-f二酯.端向化学结构改造导致卟吩周环上质子发生不同程度的吸收变化,讨论了具有叶绿素碳架的卟吩核磁光谱的变化规律. 相似文献
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孙彩云 《唐山师范学院学报》2011,33(5):34-36
以蚕沙为原料,提取叶绿素,制备成脱镁叶绿酸,再与ZnSO4反应得脱镁叶绿酸锌,所得成品为墨绿色固体,不溶于水、乙醇、丙酮及酸性溶液中,但可溶于碱性溶液中,其红外吸收光谱证明锌离子结合在脱镁叶绿酸卟啉环外侧链羧基处。 相似文献
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过渡金属Cu、Fe、Co、Ni、Zn、Mn的可溶性盐类以及稀土金属La、Ce、Pr、Nd、Sm氧化物在HClO4中溶解后在一定条件下与脱镁叶绿素合成过渡/稀土金属叶绿素;过渡金属叶绿素皂化可形成可溶性过渡金属叶绿酸盐;可溶性过渡金属叶绿酸盐又可与某些金属离子反应形成难溶性的过渡金属叶绿酸盐。通过研究这些金属叶绿素配合物的Fourier变换红外光谱、紫外可见光谱（UV-Vis）并与脱镁叶绿素或脱镁叶绿酸对比,对其谱图的数据进行了分析。 相似文献
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在酸性条件下，用过二硫酸铵和硝酸银作引发剂使喹啉和脂肪酸发生自由基烷基化反应，合成了6种具有不同长短侧链的新喹啉衍生物，合成产物为α-单取代，其结果由元素分析，UV，IR，^1HNMR所证实,对反直条件进行了探索. 相似文献
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卤代烃是有机合成中的重要中间体,借助卤代烃这个中间桥梁可合成很多化合物,研究卤代烃在有机合成中的应用意义重大.
1 卤代烃在有机合成中的应用分析
1.1 烃与烃的衍生物的桥梁
烃类化合物在一定条件下可与卤素单质发生反应生成卤代烃,卤代烃在加热条件下可发生水解反应生成醇,醇氧化可生成醛或酮,醛继续氧化可生成酸,醇和酸发生... 相似文献
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从真江蓠(Gracilaria astatica)中分离、鉴定了12个化学成分:廿二烷基-β-单甘油醚(1),十四酸(2),十五酸(3),十六酸(4),十四酸甲酯(5),十五酸甲酯(6),14-甲基-十五酸甲酯(7),十八酸甲酯(8),Z-6-十八烯酸甲酯(9),Z-6-十八烯酸乙酯(10),Z-6-十九烯酸甲酯(11)和Z-9-十六烯酸甲醇(12)。其中1是新化合物,3、6和11是在自然界中首次发现。 相似文献
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《赣南师范学院学报》2019,(3):61-64
在模拟生理酸度(pH=7.4)的条件下,利用荧光猝灭法研究姜黄素嘧啶酮衍生物6-(4-羟基-3-甲氧基苯)-4-((1Z,3E)-羟基-4-(4-羟基-3-甲氧基苯)-1,3-丁二烯-1-基)嘧啶-2(1H)-硫酮与牛血清白蛋白(BSA)的相互作用.实验结果表明:该药物分子对BSA有强的荧光猝灭作用,其猝灭机理是静态猝灭为主;该药物分子与BSA结合位点数约为1,且其结合能力优于姜黄素;运用热力学方程得出热力学参数(ΔH,ΔS)均小于0,可知药物分子与BSA的相互作用力主要是氢键和范德华作用力. 相似文献
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在高中化学金属与酸的反应中,不同金属的活泼性不同．其活动性顺序为：钾钠钙镁铝锌铁锡铅（氢）铜汞银铂金,而酸又分为氧化性酸和非氧化性酸,常见的氧化性酸有：浓硫酸、浓（稀）硝酸．因此,金属跟酸的反应是高中阶段学生存在疑虑较多的地方．现将他们归纳如下： 相似文献
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罗艳萍 《读与写:教育教学刊》2008,5(6)
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. 相似文献
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Richard Denner 《海外英语》2007,(4):14-15
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. 相似文献
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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. 相似文献
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《海外英语》2007,(5):10-11
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? 相似文献
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陈美曦 《山东教育学院学报》2008,23(2):103-107
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. 相似文献
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邱崇丙 《唐山师范学院学报》2014,(1):21-23
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。 相似文献
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《海外英语》2007,(4):36
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. 相似文献