二酸的

To improve water solubility of betulin, two acyl groups were introduced at C-3 and C-28 hydroxy groups of betulin. 3, 28-di-O-glutaryl-betulin was synthesized with pyridine as solvent and DMAP as catalyst from betulin and glutaryl anhydride.

为了增强桦木醇的亲水性，对桦木醇的C-3位、C-28位羟基进行修饰，在吡啶作溶剂、二甲基氨基吡啶作催化剂的条件下，与戊二酸酐反应合成桦木醇戊二酸酯。

The results showed that intermidiate 1, 2-propanediol-sebacate of low relative molecular mass was synthesized with toluene-p-sulfoinc acid as catalyst, benzene as watercarrying agent, and of mole ratio of sebacic acid to 1, 2-propanediol of 1:4. The glass-transition temperatures of PPSC were below 0 ℃ which confirmed that PPSC would be in a high-elastic state of ambient temperature and human body temperature. PPSC was a elastomer with moderate crosslinkage, low module and high elongation, and had rapid degradation ratio (degradation degree more than 50%) in phosphate (pH value 7.4) at 37℃.

结果表明，以对甲苯磺酸为催化剂、苯为带水剂，在酸醇比为1，4的条件下可合成较低相对分子质量的中间体癸二酸聚酯二元醇；PPSC弹性体的玻璃化转变温度在0℃以下，于室温及人体温度下处于高弹态；PPSC为适度交联的、低模量高伸长的弹性体，其在37℃、pH值为7.4的磷酸盆缓冲溶液中具有较快的降解性（降解度超过50%）。

The influence factors such as amount of catalyst,molar ratio of maleic anhydride to n-butanol,and reaction time on the yield of dibutyl maleate were discussed.

以La2(SO4)3/SiO2为催化剂，顺丁烯二酸酐和丁醇为原料，合成内增塑剂顺丁烯二酸二丁酯，探讨了催化剂用量，酐醇物质的量比以及反应时间等对收率的影响。

Ordinarily the reaction rate of amino acids is faster than that of glycols, but the carbon chain of ethylene glycol is very short, the reaction rate of L-aspartic acid was longer than that of ethylene glycol.

另外，丁二醇比乙二醇碳链长，位阻大，反应慢；通常氨基酸的反应速度要比醇快，但由于乙二醇的碳链很短，导致其比天冬氨酸的反应速度还快。

Oxidation of the terminal ch2oh group of hexoses without oxidation of the reducing function produces hexuronic acids, hooc--cho.

醛糖分子两端氧化形成糖二酸，hooc-n-cooh，例如酒产生的糖醛酸，hooc-4-cho。

The catalyzed oxidation of cyclohexanol with 30% aqueous hydrogen peroxide by mass fraction to produce adipic acid can be achieved using tungstic acid -acidic additive catalyst system in the absence of organic solvents and phase-transfer reagent.

以钨酸-酸性添加剂为催化体系，在无有机溶剂和相转移剂的情况下，催化30%过氧化氢氧化环己醇合成己二酸。

When the molar ratio of tungstic acid∶acidic organic additive∶cyclohexene∶hydrogen peroxide was 1∶1∶40∶176 (tungstic acid, 2.5 mmol) and the tungstic acid/resorcinol used as catalyst, the isolated yield of adipic acid was up to 90.9% for 8 h.

以钨酸/有机酸性添加剂为催化体系，在无有机溶剂、相转移剂的情况下，催化30%过氧化氢氧化环己烯合成己二酸。

The simple and fast determination method presented is based on initial chelation of Sn4+, Cu2+, Pb2+ and other metal ions with EDTA and its subsequent decomposition with trihydroxybenzoic acid, mercaptosuccinic acid and dithiocarbamic propanoic acid.

本文提出的简易、快速测定方法是用EDTA螯合锡、铜、铅和其它金属离子，然后分别用三羟基甲酸、巯基丁二酸和氨荒丙酸解蔽。

The major acid detected in the apple rhizosphere and the wormcast was oxalic acid, malic acid, tartaric acid, succinic acid and malonic acid, one of highest content was oxalic acid.

苹果根际和蚯蚓粪中检测到的有机酸主要有草酸、苹果酸、酒石酸、琥珀酸和丙二酸，以草酸含量为高。

An improved chemical method for the determination of the molar substitution degree of hydroxyethyl guar gum has been described.

本文用模型小分子一缩二乙二醇的醚键断裂实验证明了可行性，羟乙基瓜尔胶上的羟乙基链段与过量对甲苯磺酸-乙酸酐在130℃下反应14hr，醚键完全断裂生成酯，并在pH=11条件下煮沸1hr使酯完全水解，转变为乙二醇。

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。