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查尔酮合成方法的研究进展 总被引:4,自引:0,他引:4
查尔酮是一种黄酮类化合物,其常见合成方法是以苯甲醛和苯乙酮为原料,加入碱、酸或金属等物质作为催化剂进行醛酮缩合反应,但产率较低,副产物多。近年来查尔酮化合物的合成采用了新技术,是以苯甲醛和苯乙酮为原料,BF4作为反应溶剂,水滑石为催化剂,在温度为343 K的条件下进行反应,查尔酮产率可以达到98.5%,该法具有反应时间短、操作简便、收率高等优点。分析了近年来查尔酮几种合成方法的优缺点,催化剂的选择及其适用的条件。 相似文献
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Claisen-Schmidt缩合反应是制备α,β-不饱和醛酮的重要方法。对近几年利用Claisen-Schmidt缩合反应合成取代查尔酮衍生物的反应进行了综述,主要包括无机碱促进的Claisen-Schmidt缩合反应、有机碱促进的Claisen-Schmidt缩合反应、酸促进的Claisen-Schmidt缩合反应和金属氧化物促进的Claisen-Schmidt缩合反应。 相似文献
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固体超强碱催化环己酮羟醛缩合反应的研究 总被引:2,自引:0,他引:2
环己酮自身羟醛缩合产物2-(1-环己烯基)环己酮与2-环己亚烷基环己酮是合成柑桔类杀菌防腐剂邻苯基苯酚(OPP)的中间体,传统合成方法主要采用液体碱等均相催化剂,催化效率低且产品难以分离,为此本文以改进的Na/NaOH/γ-Al2O3型固体超强碱为催化剂,探索了一种新的合成工艺,同时对反应条件进行了优化.实验结果表明:反应温度为190 ℃、催化剂用量为原料质量的10%、反应时间为3 h时,二聚物产率最高,达85.66%.该合成工艺催化效率高,产品易分离,后处理简单,具有一定的工业应用前景. 相似文献
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利用Benson基团贡献法估算了饱和脂肪酸或酯与甲醛羟醛缩合反应生成多一个碳的α,β-不饱和脂肪酸或酯的标准生成焓、标准熵和摩尔比定压热容,对反应体系的热力学性质进行计算。分析了反应的方向与限度,考察了温度对反应热力学性质的影响,比较了热力学数据随产物分子结构的变化规律。结果表明:在498—698 K的温度区间内,文中涉及的生成通式为CH=2CR1COOH的反应,均为自发放热反应。当R1为H时,较烷烃取代基自发放热反应程度偏小,R1为烷烃取代基时,其碳链的增长对羟醛缩合反应热力学性质的影响可以忽略。生成通式为CH=2CHCOOR2的反应,反应热随R2取代基上与氧相连碳原子由—CH3,—CH2变化到—CH而降低,反应程度下降。 相似文献
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Passing a catalytic amount of electricity (7.5 × 10?3 F mol?1) into solution of aldehydes in DMF leads to formation of α, β-unsaturated carbonyl compounds through the aldol-type condensation with extremely high current efficiency (1 × 104%). 相似文献
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Olefin-aldehyde condensation reaction on solid acids 总被引:1,自引:0,他引:1
A vapor phase octadiene synthesis from isobutyraldehyde and isobutene was examined over various catalysts at 523 K. Although solid bases were totally inactive, solid acids exhibited high activity to yield dienes. Niobic acid was found to be an excellent catalyst in the total yield. WO3/TiO2 and Ag-O/SiO2 were also excellent catalysts with respect to the diene selectivity (98–99%), though the yields were slightly lower than that of niobic acid. Acid strength required for the reaction was found to be in the range of −8.2
Ho −3.0. Reactions from furan derivatives and octanol were also investigated. 相似文献
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The effect of chemisorbing water on three catalysts previously evaluated in the acetone condensation reaction has been studied.
The active sites in that reaction are Lewis acid sites present either on the surface of alumina or of nonframework alumina
in zeolites. These sites are poisoned by water and the reaction rate decreases at the pace of the loss of Lewis sites. The
stoichiometry of the poisoning reactions is one water molecule per site on alumina and two water molecules per site on nonframework
alumina.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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采用固相反应法以硼酸和磷酸二氢铵为原料制备磷酸硼 (BPO4)产品,研究了原料配比(氧化硼与五氧化二磷物质的量比)、反应温度对产物化学组成和结构的影响,确定的最佳工艺条件为:n(氧化硼)/n(五氧化二磷)为1.0~1.05,反应温度为850~1 000 ℃。用红外光谱(IR)、X射线衍射(XRD)研究了产品的物相结构。温度是影响物相结构的主要因素,当固相反应温度达到1 000 ℃时,所得产品晶体结构完整,产品质量稳定。采用热重-差热分析(TG-DTA)和差示扫描量热法(DSC)研究了高温固相反应过程,提出了该工艺的反应机理,并确定了在技术上、经济上可行的工艺路线。 相似文献
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新型催化剂上醇醛缩合的进展 总被引:1,自引:0,他引:1
综述了近几年来在醇醛缩合反应中,各种固体催化剂的研究进展,其中有固体酸碱催化剂及新型的固体手性催化剂,评论了各自的反应活性及影响因素。 相似文献
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固相反应合成Al4SiC4材料 总被引:1,自引:0,他引:1
采用粒度14μm的磨料级碳化硅,粒度10 μm的工业级金属铝粉和粒度5 μm的工业级炭黑粉为原料,按SiCAlC质量比为225919配料制成试样,在氩气保护下,分别在1200℃8 h、1600℃2 h和1650℃2 h烧成,研究了通过固相反应合成Al4SiC4材料的条件和动力学过程.通过X射线衍射仪进行物相分析,扫描电子显微镜和透射电子显微镜的形貌分析以及能谱分析确定成分.结果表明反应体系在1200℃以下,铝和炭黑反应首先生成中间相Al4C3;从1200℃开始通过SiC+Al4C3=Al4SiC4固相反应生成Al4SiC4;当合成温度达到1650℃时,获得Al4SiC4材料;制备的Al4SiC4材料的颗粒均匀,尺寸在几百纳米到几微米之间. 相似文献
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A variety of catalysts consisting of MgO, SiO2, Al2O3 and ZrO2, with and without added cesium, were evaluated in the aldol condensation of propionic acid with formaldehyde to produce methacrylic acid. Reactions were performed in a fixed-bed reactor operating at atmospheric pressure and 598 K. Stepwise TPD of pre-adsorbed NH3 and CO2 was used to estimate the number and strength of surface acid and base sites, respectively. Both a strong solid base such as MgO and a non-basic solid such as SiO2 were ineffective at catalyzing the aldol condensation reaction. However, Cs-loaded silica and alumina exhibited moderate activity and high selectivity for the reaction. Results from reactivity measurements and surface characterization suggest that both acid and base sites are needed to catalyze the reaction, and the observed rates over the bifunctional ZrO2 catalyst support this hypothesis. A reversible inhibition of the rate by added water was observed over Cs–SiO2 and is attributed to migration and agglomeration of the cesium on the support in the presence of water. 相似文献