氯或溴甲基化

2021-07-07 来源：步旅网

The optimum conditions which we developed for the chlorornethylation of benzene involved the reaction of 3 moioles of benzene, 2 equivalents of trioxymethylene and 30 g. of zinc chloride in 200 ml. of glacial acetic acid with excess anhydrous hydrogen chloride (passed in tosaturation during the first 3 hours) at 60℃for 72 hours. The yield of benzyl chlorideis 65%, based on formaldehyde. Toluene was much more reactive-a 57% yield of the product was obtained in only 18 hours with half the quantity of the zinc chloride catalyst. In ease of manipulation and quality of

productthe procedure proved quite advantageous over that described byBlanc JAC.

To a stirred mixture of the ether 4 (10.0 g, 0.05mol) and paraformaldehyde(1.5 g, 0.05mol) in hexane (100ml) was added dropwise conc. HCl (50ml)at room temperature. After the solid was dissolved completely, the mixturewas stirred for another 30min and then stood still. The two layers wereseparated. The aqueous layer was extracted with hexane (2 50ml) again.The organic layer and the extracts were combined, washed with brine,dried, and evaporated in vacuo. Silica gel chromatography of the residueprovided the benzyl chloride 5 as colorless oil in 90% yield (11.1 g).

在三口瓶中加入 3 2 m L 3 6 ％( 0 .4 2 m o 1 ) 甲醛水溶液,41 m L ( 0 .4 2 mol) 水杨醛和2 7 0 mL浓盐酸，冷却搅拌下通人干燥的 H C 1气体，保持温度在 l 5～2 0℃，约 2h出现白色固体,继续通 HC1气体 2 .5h ,停止反应,将反应容器密封放置24h。

典型的实验方法即在三颈烧瓶中加入多聚甲醛1.6 g，无水氯化锌4.0 g 和浓盐酸6 mL , 加热搅拌,当温度升至60 ℃时,加入烷基苯0.2 mol,并迅速通入由浓硫酸和氯化钠反应产生的干燥氯化氢气体,通过浓硫酸的滴加速度控制通入气体的量,多余气体用水吸收. 反应6 h 后结束,冷却后于分液漏斗中分液,有机层依次用10 % 碳酸钠水溶液洗涤2 次、蒸馏水洗涤3 次, 然后用无水硫酸钠干燥, 过滤, 蒸除多余的烷基苯,最后减压蒸馏得到烷基苄氯, 称重计算收率.

In a 2-l. round-bottomed flask, equipped with a sealed mechanical stirrer (Note 1), a gas inlet tube, and a reflux condenser, are placed 200 g. (1.66 moles) of mesitylene, 1 l. of concentrated hydrochloric acid, and 63 ml. (0.84 mole) of formaldehyde solution (concentration, 37%) (Note 2). Hydrogen chloride is introduced below the surface of the mixture (Note 3), which is stirred vigorously and heated in a water bath kept at

55.These conditions are maintained throughout the reaction, which requires a total of 5.5 hours. At the halfway point, an additional 63 ml. (0.84 mole) of formaldehyde solution is added (Note 4).Organic syntheses

在氯甲基化反应过程中，多聚甲醛的溶解是很重要的，它直接影响着产品的质量和收率，因邻二甲氧基苯之前用盐酸将多聚甲醛充分溶解。经多次试验在 4 0～4 5 ℃保温 1小时即可全溶。全溶后多聚甲醛以甲醛分子状态存在，当加入邻二甲氧基苯的氯仿溶液时，氯甲基化反应即开始，经试验该反应在 2 8 ～3 0 ℃约需 5小时反应完成。反应温度不能太高，否则 3 ，4一二甲氧基氯苄将分解并有副产物形成。 4,6 - 二甲基一 1,3 一二( 溴甲基)苯的合成 250mL三颈瓶中加入多聚甲醛 4.5g ( 0.15mol)、溴化钠 18.1g (0.17mol ) 、间二甲苯 9．2 mL (0.075mol ) 及冰醋酸 78mL。将 36mL浓硫酸与等体积冰醋酸配制成混合液，剧烈搅拌下缓慢滴加到三颈瓶中，升温至 8 0～8 5 ℃，反应 4～6h。冷却至室温，溶液倾倒人 4 0 0 m L水中，析出白色絮状固体，抽滤，水洗至中性．烘箱 ( 3 0～3 5 ℃) 干燥。62%

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氯或溴甲基化