The bromination of pyridine
The bromination of pyridine
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DOI：
10.1021/ja01378a031
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发表时间：
1929-01-01
影响因子：
15
通讯作者：
McElvain, SM
中科院分区：
文献类型：
--
作者：
Englert, SME;McElvain, SM
Diehl7在水溶液中不能从溴和吡啶中得到确定的化合物，但在氯仿溶液中得到了一种分子式为CsHsN-Br的化合物。经过分析，这种四溴化物失去了溴，变成了一种化合物，这种化合物的分子式为CsHsN'Br^ Barthe8，这种化合物是从吡啶和溴中得到的，他给它定名为C5H5N-Br。特罗布里奇和迪尔还制备了吡啶盐类过溴化物。通过将溴放入氢溴吡啶水溶液中，他们得到了两种过溴化物，其中一种含有41.95%的溴，另一种含有33.66%的溴，以过溴溴的形式存在。后一种化合物在93℃熔化，分子式为C5H5N-HBr-Br。假设含过溴41.95%的过溴是C5HsN-HBr' br2和C5H6N-HBr-Br的混合物。这些研究人员还在水溶液中制备了一种过溴，并将其定式为05 6·2 20。它在118-120熔化，含有67.96%的过溴溴。在这里报告的工作中，发现冰乙酸是比水更好的溶剂，因为两种反应物（溴和氢溴吡啶）在这种介质中都很容易溶解，而所形成的过溴化物，在温乙酸中很容易溶解，在冷酸中却很不溶解。从一摩尔溴和一摩尔氢溴吡啶在乙酸溶液中得到过溴，该过溴在132-134℃熔化。产率为理论产率的95-97%。虽然该配方要求50%的过溴含量，但在132-134熔化的产品中只发现47%的过溴。一摩尔氢溴化吡啶和半摩尔溴在冰醋酸溶液中得到过溴，在101-103度熔化，含有39.7%的过溴化溴。在分子式CsHeN-HBr-Br的化合物中，过溴的含量为33.3%。作者还不能为这些过溴化物指定令人满意的公式，但希望进一步的工作将对这个问题有所启发。曾尝试用盐酸吡啶代替氢溴化吡啶制备过溴化物，但发现盐酸的得率比氢溴化物低得多，而且盐酸吡啶的过溴化物极易潮解，难以处理。当这些过溴化物在回流冷凝器下加热到230-250℃时，溴化氢发生剧烈演化，生成3-溴和3,5 -二溴吡啶。过溴含有47%
Diehl7 were unable to obtain a definite compound from bromine and pyridine in aqueous solution but in chloroform solution they obtained a compound which appeared to have the formula CsHsN-Br.!. On standing this tetrabromide lost bromine and passed into a compound which analysis showed to have the formula CsHsN'Br^ Barthe8 obtained from pyridine and bromine a perbromide to which he assigned the formula C5H5N-Br. Trowbridge and Diehl also prepared perbromides of salts of pyridine. By passing bromine into an aqueous solution of pyridine hydrobromide they obtainedtwo perbromides, one of which contained 41.95% of bromine and the other 33.66% of bromine that was present as perbromide bromine. The latter compound melted at 93 and the formula C5H5N-HBr-Br was assigned to it. The perbromide containing 41.95% of perbromide bromine was assumed to be a mixture of C5HsN-HBr'Br2and C5H6N-HBr-Br. These investigators also prepared a perbromide in aqueous solution to which they assigned the formula 05 6· 2 20. It melted at118-120 and contained 67.96% of perbromide bromine. In the work which is reported here it was found that glacial acetic acid was a much better solvent than water for the preparation of these per-bromides because both reactants (bromine and pyridine hydrobromide) were quite soluble in this mediumand the perbromides which were formed, while very soluble in warm acetic acid, were quite insoluble in the cold acid. From one mole of bromine and one mole of pyridine hydrobromide in acetic acid solution there was obtained a perbromide that melted at 132-134. The yield was 95-97% of the theoretical based on the formation of 06 5· 2. While this formula requires 50% perbromide bromine content, there was found only 47% of perbromide bromine in the product that melted at 132-134.One mole of pyridine hydrobromideand one-half mole of bromine in glacial acetic acid solution gave a perbromide that melted at 101-103 and had 39.7% of perbromide bromine. The perbromide bromine in the compound of the formula CsHeN-HBr-Br amounts to 33.3%. The authors are not able as yet to assign satisfactory formulas to these perbromides but it is hoped that further work will throw some light on this subject. An attempt was made to use pyridine hydrochloride insteadof pyridine hydrobromide for the preparation ofthese perbromides but it was found that the yields from the hydrochloride were considerably lower than those from the hydrobromide and that the perbromides of pyridine hydrochloride were very deliquescent and quite difficult to handle. When these perbromides were heated at 230-250 under a reflux conden-ser, there was a vigorous evolution of hydrogen bromide with the formation of 3-bromo-and 3, 5-dibromopyridine. The perbromide containing 47%