乙酸甲酯

The yield of the 3, 4-dihydropyrimidine-2(1H)-one was up to 95.4% under mole ratio of anisaldehyde, methyl acetoactate and urea is 1:2:5, ion-exchange membrane is 3 g, ethyl alcohol as solvent and refluxing for 2 h.

当对羟基苯甲醛、乙酰乙酸甲酯与脲的摩尔比为1：2：5，乙醇作溶剂，3 g离子交换膜，回流2 h，产物收率达95.4%。

Methoxycarbonyl-4-(4-methoxyphenyl )-6-methyl-3, 4-dihydropyrimidine-2(1H)-one was synthesized from anisaldehyde, methyl acetoactate and urea in presence of HF-1O1 strong acidic ion-exchange membrane.

在HF-101强酸性离子交换膜的存在下，由对羟基苯甲醛、乙酰乙酸甲酯与脲一步合成了5－甲氧羰基－4－（4－甲氧苯基）－6－甲基－3，4－二氢嘧啶－2(1H)－酮。

Aim To synthesize methyl 2-(4-methoxyphenyl)-2-oxoacetate from the ascidian Polycarpa aurata.

目的合成从太平洋海鞘 Polycarpa aurata中提取的天然产物2-(4-甲氧基苯基)-2-氧代乙酸甲酯。

In this paper, we recounted the recent development of solid supeeracids and their appliance in esterification.

采用溶胶一凝胶法制备SO_4~(2-)/TiO_2-SiO_2固体超强酸催化剂，考察它在乙酸甲酯酯化反应中的催化活性。

Cephalotaxine ester of 2-oxo-6-methylheptanoic acid was treated with lithium diisopropylamide and Me O-(1-methoxyisopropyl)glycolate to give a mixture of homoisoharringtonine and its stereoisomers with 56% yield. The four stereoisomers separated by TLC showed identical mass spectra and almost superimposed IR but with different 1H NMR spectra. The configuration of the 2'-C and 3'-C of the four isomers were postulated based upon their 1H NMR spectra as compared with the 1H NMR spectra of isoharringtonine and its stereoisomers.

2-氧代-6-甲基庚酰基三尖杉碱(3)与0-(1-甲氧基异丙基)羟基乙酸甲酯(4)在强碱性试剂二异丙胺锂存在下，起亲核加成反应，反应中间体5在室温用酸性丙酮水解，得到一种新的三尖杉酯类生物碱一一高异三尖杉酯碱(6c)及其立体异构体(6a、6b、6d)的混合物，产率56%、通过制备薄层层析分得这四个立体异构体，它们的1H NMR和异三尖杉酯碱及其立体异构体的1H NMR类似，推定了它们的绝对构型。

3 Explain why propanoic acid boils at 141℃,but methyl acetate boils at 57℃.

解释为什么丙酸沸点为141℃，而乙酸甲酯沸点为57℃。

This invention publishes a preparation method for methyl acetate and a reaction distillation column with combined trapezoid spray trays.

本发明公开了一种乙酸甲酯的制备方法和具有立体传质塔板的反应精馏塔。

The results showed that the optimal parameters of transesterification reaction were: molar ratio of methyl acetate to oil 14:1, 30% enzyme added based on oil weight, temperature 40℃ and reaction time 14 h.

研究结果表明，最佳酯交换条件为：脂肪酶Novozym 435加入量为棉籽油质量的30%，乙酸甲酯和棉籽油的摩尔比14：1，反应温度40℃，反应时间14 h。

We have concluded that the main losing activity reason of SO_4~(2-)/TiO_2-SiO_2 solid superacid catalysts used in synthesis of methyl acetate is the accumulated carbon of catalytic surface and the loss of SO_4~(2-).

3对催化剂的失活机理进行讨论，结果表明用于乙酸甲酯酯化反应的SO_4~(2-)/TiO_2-SiO_2固体超强酸催化剂失活的主要原因是催化剂表面积碳和SO_4~(2-)流失。

Purified sucralose-6-acetate which had been recrystallized was hydrolyzed in th system of sodium methoxide/methanol solution, and the mixture was quenched with H+ ion exchange resin, and cake was washed with methanol. The eluate was concentrated to remove methanol and methyl acetate. The aqueous solution was decoloured with active carbon. The filtrate solution was concentrated and crystallized above 38℃for sever hours, the product sucralose was collected.

重结晶的三氯蔗糖-6-乙酸酯于CH3ONa/CH3OH体系中醇解，用H+型阳离子交换树脂中和，蒸去甲醇、乙酸甲酯等，在水相中用活性炭脱色，水溶液经浓缩，在38℃以上结晶数小时，分离得三氯蔗糖。

According to the clear water experiment, aeration performance of the new equipment is good with high total oxygen transfer coefficient and oxygen utilization ratio.

曝气设备的动力效率在叶轮转速为120rpm～150rpm时取得最大值，此时氧利用率和充氧能力也具有较高值。

The environmental stability of that world - including its crushing pressures and icy darkness - means that some of its most famous inhabitants have survived for eons as evolutionary throwbacks, their bodies undergoing little change.

稳定的海底环境─包括能把人压扁的压力和冰冷的黑暗─意谓海底某些最知名的栖居生物已以演化返祖的样态活了万世，形体几无变化。