303. Physicochemical studies of some cyclic carbonates. Part II. The rates of hydrolysis of ethylene carbonate and of propylene carbonate
303. Physicochemical studies of some cyclic carbonates. Part II. The rates of hydrolysis of ethylene carbonate and of propylene carbonate
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303.一些环状碳酸酯的物理化学研究。
DOI：
10.1039/jr9590001576
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发表时间：
1959
期刊：
影响因子：
--
通讯作者：
W. Lee
中科院分区：
文献类型：
--
作者：
R. Kempa;W. Lee
本文研究了碳酸亚乙酯和碳酸亚丙酯在碱性水介质中25 ″下的水解动力学，其速率常数ho~ 1分别为48.8和17.81。摩尔-l最小值- l的范围内。用电导法研究了这两种化合物水催化水解的起始速率，在25 ℃时，起始速率常数KH，O分别为14.2 × min和7.1 × min。l的范围内。在180 ℃时，碳酸亚乙酯的k= 10为5-7 × 10- 1 min。l，导致其初始水解的活化能为22.5kcal/l。据报道，用于冰点下降法的碳酸乙烯酯是不吸湿的，并且没有采取预防措施来防止从空气中吸收水分。然而，我们发现，放在恒温器中塞住塞子的电导池中的仔细纯化的环状碳酸酯样品的电导率逐渐增加。该效果似乎是由于水解;由于旨在在水中和水溶液中进行反应，为了研究环状碳酸酯对金属离子的络合物形成，似乎感兴趣的是获得碳酸亚乙酯和碳酸亚丙酯在碱性水溶液和水中的水解速率。碱性水解碱性水解后进行滴定，如Skrabal和Baltadenewa对开链酯的研究2中所述，其速率比水分子水解的速率大得多，因此我们可以将碱性溶液中的速率方程写成：
The kinetics of the hydrolyses of ethylene carbonate and propylene (ie, methylethylene) carbonate, in alkaline aqueous media, at 25” have been studied; rate constants, ho~, are 48.8 and 17.8 1. mole-l min.-l, respectively. Conductimetry was used to study the initial rates of the water-catalysed hydrolyses of these two compounds; at 25O, the initial rate constants KH, O were 14.2 x and 7.1 x min.-l, respectively. At 18O, k=, o for ethylene carbonate was 5-7 x 10-rnin.-l, leading to an activation energy for its initial hydrolysis of 22.5 kcal./mole.ETHYLENE CARBONATE for use in cryoscopy was reported to be non-hygroscopic, and no precautions were taken to prevent the absorption of moisture from the air. l We have found, however, that the conductivity of samples of carefully purified cyclic carbonates, left in stoppered conductivity cells in a thermostat, progressively increases. The effect appeared to be due to hydrolysis; as it is intended to carry out reactions in water, and in aqueous solutions, in order to study complex-formation of metal ions by cyclic carbonates, it seemed of interest to obtain rates of hydrolysis of ethylene carbonate and of propylene carbonate, in aqueous alkaline solution and in water. Alkaline Hydrolysis.-Alkaline hydrolyses were followed by titration, as in Skrabal and Baltadschiewa’s studies of open-chain esters2 The rates were so much greater than those for hydrolysis by water molecules that we may write for the rate equation in alkaline solution: