Выход кислоты по методе около 55%... Потери при переходах на эфир и обратно неминуемы... И получится из 100 г исходника (не очень-то и дешевого) понты. "Эфирная" овчинка выделки не стоитНЕКОЗЛЮ писал(а):А почему бы не перегнать ее эфир (например, метиловый)?
Тогда возможно и вашей лабы хватит
Уважаемый rombach а что это за методика с таким хорошим выходом троповой кислоты? Поделитесь методой если она у Вас есть (метода с использованием реактива Иванова не рулит). И что нет никаких побочных реакций? По методике, имеющейся у меня, кроме троповой к-ты образуется так же 2-фенилакриловая (атроповая) к-та.rombach писал(а):Кислота вообще-то твердая. Плавится под 130С. Получается из фенилуксусной с выходом 80%, отделяется фильтрованием. Зачем перегонять-то?
Magnesium (97.3 g.) and 2 liters of anhydrous ether were placed in a 5-liter, 3-necked flask fitted with a stirrer, dropping funnel and a 2-ft. reflux condenser. About 2 cc. of ethyl bromide and 10 cc. of isopropyl chloride were added, and the mixture was warmed to initiate the reaction. Isopropyl chloride (330 g.) was then added, dropwise, at such a rate that the mixture refluxed. After all of the chloride had been added, the mixture was refluxed for one-half hour. Phenylacetic acid (240 g.), dissolved in 2 liters of dry benzene, was added to the stirred solution at such a rate that the mixture refluxed. After the addition was completed, the material was refluxed (about 12 hours) until no more gas was evolved. Since a large volume of propane was evolved during and after the addition of the phenylacetic acid, this operation should be carried out in a hood or the gas should he passed through a tube which carries it out of the laboratory. The mixture was cooled in an ice-bath, and the dropping funnel was replaced by the side-arm of a distillation flask. The side-arm was made of wide glass tubing and was bent at a right angle. The horizontal section of the side-arm should be about 6 inches long and the vertical section should be long enough so that after it has been inserted into the reaction flask the end of the side-arm is about 1 inch above the surface of the stirred liquid. Paraformaldehyde (140 g.) (Mallinckrodt), which had been dried for two days in a desiccator over phosphorus pentoxide, was placed in the distillation flask which was heated in an oil-bath at 180-200'. The formaldehyde was carried into the vigorously-stirred mixture by a slow stredm of dry nitrogen. The latter operation required from three to three and one-half hours. The reaction mixture was then poured into a mixture of 300 cc. of concd. sulfuric acid and 3 liters of finely crushed ice which had been placed in a 2-gal. crock, and the mixture was stirred for one-half hour. The solid material was removed by filtration, the organic layer separated, and the aqueous layer, and also the filtered solid, were placed in the original reaction flask. The mixture was warmed on a steam-bath for one-half hour, or until most of the solid had disappeared, then thoroughly cooled, filtered, and extracted with three 300-cc. portions of ether. The ether extracts and the organic layer were combined, and the solvents were removed under reduced pressure until the volume in the distillation flask had been reduced to about 500 cc. The mixture was then cooled for 12 hours, the precipitated tropic acid filtered, the filtrate concentrated to one-half of its original volume, cooled and more tropic acid removed by filtration. The crude tropic acid was heated with 500 cc. of benzene to dissolve unchanged phenylacetic acid, cooled, filtered, and washed with a small amount of cold benzene. The air-dried acid melted at 116-117"; yield 207-245 g. (71-83%).
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