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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%. 相似文献
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以萘和乙酰氯为原料,经Friedel-Crafts酰基化反应生成中间体α-萘乙酮,然后该中间体与羟胺盐酸盐发生肟化反应制得α-萘乙酮肟.研究了三氯化铝的用量、反应温度、乙酰氯加入方式对酰化反应的影响以及水用量、羟胺盐酸盐用量、碱用量对肟化反应的影响.适宜的反应条件为:酰化反应的乙酰氯与三氯化铝的摩尔比为1∶1.5,反应温度为(25±2)℃,乙酰氯以0.3 mL/min的速度加入;肟化反应的α-萘乙酮∶羟胺盐酸盐∶水∶碱(摩尔比)为1∶1.5~2.0∶4.30~34.0∶5.0.在此反应条件下,产物总收率达87.0%.改进后的实验具有合成过程操作方便、分离提纯程序简单、安全等优点,对工业生产及实验教学有积极的指导意义. 相似文献
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探索了酸性功能化离子液体1-(3-磺酸基)丙基-3-甲基咪唑磷酸盐的微波合成及在Mannich反应中的催化活性.利用正交实验的方法,考察了反应条件对产率的影响,结果表明,当n(对硝基苯甲醛)∶n(环已酮)∶n(苯胺)=1∶1∶1.5,催化剂用量为0.7g,微波辐射功率为400W,辐射10min时,产率可达84.56%. 相似文献
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研究了以乙酸酐和2-羟基苯甲酸为原料,以对甲基苯磺酸为催化剂合成2-乙酰氧基苯甲酸的清洁合成工艺,考察了影响合成反应的诸多因素。最佳工艺条件是:物质的量n的比为n(2-羟基苯甲酸)∶n(乙酸酐)∶n(对甲基苯磺酸)=1.0∶2.0∶0.025,反应温度为80~85℃,反应时间为60min,2-乙酰氧基苯甲酸的收率为88.35%。该工艺具有原料价廉易得、不腐蚀设备和无环境污染等优点,可实现清洁化生产。 相似文献
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以硅胶负载硅钨酸为催化剂,通过丁醛与1,2-丙二醇反应合成了丁醛1,2-丙二醇缩醛.较系统地研究了醛醇量比、催化剂用量、带水剂用量及反应时间等条件对收率的影响.结果表明:在丁醛用量为0.20 mol,n(丁醛)∶n(1,2-丙二醇)=1∶1.3,催化剂用量为0.1 g,环己烷为带水剂用量为4 mL,反应时间30 min的优化条件下,丁醛1,2-丙二醇缩醛的收率可达82.6%. 相似文献
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以HBr为溴化剂,H2 O2为氧化剂,在水相中合成了α-溴代苯乙酮.通过实验优化并确定的工艺条件为:n(苯乙烯):n(HBr):n(H2 O2)=1:1.5:2;反应温度为85℃;反应时间为2.5 h;收率可达94%.本方法采用绿色氧化剂H2 O2,且不使用任何有机溶剂,对环境无污染,原子利用率高,操作简单,生产成本低,适合于规模化生产. 相似文献
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以二氧化硅负载Dawson型磷钨酸H6P2W18O62/SiO2为催化剂,采用环己酮和1,2-丙二醇为原料合成环己酮1,2-丙二醇缩酮.探讨H6P2W18O62/SiO2对缩酮反应的催化活性,较系统地研究了各种因素对产物收率的影响.实验表明:H6P2W18O62/SiO2是合成环己酮1,2-丙二醇缩酮的良好催化剂,在n(环己酮)∶n(1,2-丙二醇)=1∶1.5,带水剂环己烷6 mL,催化剂用量占反应物料总质量的0.6%,反应时间60 min的优化条件下,环己酮1,2-丙二醇缩酮的收率可达85.4%. 相似文献
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报道了以固体超强酸SO2-4/TiO2-WO3为催化剂,通过苯甲醛和乙二醇反应合成了苯甲醛乙二醇缩醛,探讨了SO2-4/TiO2-WO3对缩醛反应的催化活性,较系统地研究了醛醇物质的量比,催化剂用量,反应时间诸因素对产品收率的影响.实验表明:SO2-4/TiO2-WO3是合成苯甲醛乙二醇缩醛的良好催化剂,在n(醇)∶n(醛)=1.25∶1,催化剂用量为反应物料总质量的0 50%,环己烷为带水剂,反应时间50min的优化条件下,苯甲醛乙二醇缩醛的收率可达77 3%. 相似文献
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以H4SiW6Mo6O40/SiO2为催化剂,通过异丁醛和1,2-丙二醇为原料合成异丁醛1,2-丙二醇缩醛,探讨了H4SiW6Mo6O40/SiO2催化剂对缩醛反应的催化活性,较系统地研究了原料量比,催化剂用量,反应时间诸因素对产品收率的影响.实验表明:H4SiW6Mo6O40/SiO2是合成异丁醛1,2-丙二醇缩醛的良好催化剂,在n(1,2-丙二醇)∶n(异丁醛)=1.5∶1,催化剂用量为反应物料总质量的1.2%,环己烷为带水剂,反应时间1.0 h的优化条件下,异丁醛1,2-丙二醇缩醛的收率可达75.2%. 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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《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
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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. 相似文献
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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. 相似文献
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RUZBEHANI Mohsen 《重庆大学学报(英文版)》2004,3(1):20-25
1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec… 相似文献
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唐芳 《读与写:教育教学刊》2008,5(6)
During interview with English majors, it was found that a majority of students expressed disappointment with their experience of English literature classes. Students' dislike of learning English literature appears to be the major problem of teaching English literature in China. Reader response approach is a good way to solve this problem. In this paper, I explain the rationale behind the reader response approach, such as its origin, definition, features, assumptions, and strategies. Then I illustrate how reader response approach works as a teaching strategy by presenting several teaching models. At last I evaluate its usefuiness for teachers and present the advantages of reader response approach in Chinese context. 相似文献