Heat capacities and entropies of organic compounds.: III.: Methylamine from 11.5°K.: To the boiling point.: Heat of vaporization and vapor pressure.: The entropy from molecular data
Heat capacities and entropies of organic compounds.: III.: Methylamine from 11.5°K.: To the boiling point.: Heat of vaporization and vapor pressure.: The entropy from molecular data
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DOI：
10.1021/ja01288a054
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发表时间：
1937-07-01
影响因子：
15
通讯作者：
Messerly, GH
中科院分区：
文献类型：
--
作者：
Aston, JG;Siller, CW;Messerly, GH
迄今为止，还没有关于简单胺的熵和自由能的工作出现。目前对甲胺的研究是一系列研究中的第一个，其目的是获得低级伯、仲和叔脂肪胺的数据。由于乙烷和甲胺的相似性，本文报道的结果更令人感兴趣。在乙烷的情况下，根据热数据和第三定律计算出的气体在沸点的熵比根据假设气体中的甲基自由内旋转的分子数据计算出的熵低1.5eu。 1 因为第三定律值与乙烷-乙烯平衡计算值非常一致，Kemp 和 Pitzer 发现有必要放弃气体自由旋转的假设并假设势垒为 3150 cal。四甲基甲烷和甲醇已经显示出类似的差异，分别为 2、3，即甲基为 1.7 eu。 Kassel3指出，甲醇平衡的数据与3000卡势垒的假设是一致的。对于甲醇，尽管他犹豫是否仅根据这一证据接受如此高的价值。在下面的段落中表明，假设自由旋转计算的甲胺的熵与热数据和第三定律计算的熵相差相同的量。 甲胺的制备和纯化。-为了消除二甲胺和三甲胺，根据常规程序通过重排溴乙酰胺来制备该化合物。通过从无水乙醇中重结晶尽可能地除去盐酸盐中的氯化铵。通过将饱和溶液滴到固体氢氧化钾上并用氢氧化钾棒干燥所得气体，然后在钢瓶中冷凝，由盐酸盐获得胺。然后将胺在 10 atm 下蒸馏两次。通过装满玻璃螺旋的高效玻璃分馏柱（10-15 理论塔板）。 4* 主要部分的一部分是
No work has so far appeared on the entropy and free energy of simple amines. The present study of methylamine is the first of a series of investigations whose purpose is to obtain such data for the lower primary, secondary, and tertiary aliphatic amines. The results herein reported are of further interest because of the similarity of ethane and methylamine. In the case of ethane the entropy of the gas at theboiling point calculated from thermal data and the third law is 1.5 eu lower than that calculated from the molecular data assuming free internal rotation of the methyl groups in the gas. 1 Be-cause the third law value is in good agreement with the value calculated from the ethane-ethyl-ene equilibrium Kemp and Pitzer have found it necessary to discard the assumption of free rotation in the gas and to assume a potential barrier of 3150 cal. Tetramethylmethane and methyl alcohol had already shown similar discrepancies, 2, 3 namely, 1.7 eu for methyl groups in each case. Kassel3 pointed out that the data on the methanol equilibrium are consistent with the assumption of a potential barrier of 3000 cal. for methyl alcohol, although he hesitated to accept such a high value solely on this evidence. In the following paragraphs it is shown that the entropy calculated for methylamine assum-ing free rotation differs by a like amount from that from the thermal dataand the third law.Preparation and Purification of Methylamine.—In order to eliminate di-and trimethylamine the compound was prepared by rearrangement of bromoacetamide ac-cording to the usual procedure. The hydrochloride was freed as far as possible from ammonium chlorideby recrystallization from anhydrous ethyl alcohol. The amine was obtained from the hydrochloride by dropping a saturated solution onto solid potassiumhydroxide and drying the resulting gas over potassium hydroxide sticks before condensing in steel cylinders. The amine was then twice distilled at 10 atm. through an efficient glass fractionating column packed with glass helices (10-15 theoretical plates). 4* A portion of the main fraction was