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Reaction of the Bromo Ketones with Methylamine.-One-tenth of a mole of the bromo ketone was added drop-wise with vigorous stirring to 0.25 mole of methylamine (in the form of a 30% solution in absolute alcohol) over the required period of time (one hour for bromopropiophenone, seventeen to eighteen hours for a-bromobutyrophenone, twenty-four hours for a-bromovalerophenone). The reaction flask was immersed in ice water during the reaction and stirring was continued for one-half to three-quarters of an hour after the addition of the bromo compound. Cold, coned. hydrochloric acid was then added very slowly along with some finely cracked ice until the mixture was acidic. If it became warm the product turned very dark in color and a larger pro- portion of tar was produced. At this point the reaction mixture was orange or red due t o the presence of some bromo ketone that had not reacted and to the formation of cer- tain tarry by-products. These were extracted with ether from the water layer and the bromo ketone recovered. The water layer was evaporated to dryness in DUGUO, treated with a little chloroform and evaporated to dryness again to assist in removing the moisture from the rather hard mass. After standing in a vacuum desiccator for a day, the residue was extracted several times with fresh portions of chloroform and each time the insoluble crystals of methylamine hydrochloride were filtered. The chloroform solution was then evaporated until it was very concentrated, and acetone was added to cause the crystallization of the amino ketone hydrochloride. Recrystallization was carried out by dissolving in a small amount of alcohol, filtering, and adding about twice the volume of acetone in small portions. |
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2楼2014-02-13 18:20:27