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3. The filtration must be done rapidly, preferably through a preheated funnel. Any material which crystallizes in the receiver is brought into solution again by warming on the steam bath.
. 4. Alternatively, the reaction mixture may be cooled at once and the solid product removed. The filtrate is successively concentrated and chilled three times, each crop of crystals being rinsed with acetone. For example, in a run using 480 g. of aceto-phenone, the amounts obtained were 297, 92, 53, and 16 g. respectively, and 42 g. from the acetone washings, making a total of 500 g. or 66 per cent of the theoretical amount.
5. The excess dimethylamine hydrochloride is held in solution by the acetone.
6. The material is somewhat hygroscopic and holds traces of water tenaciously. The melting point is lowered by the presence of moisture; a preliminary shrinking is usually observed.
7. After it has been dried for an additional four hours, the product melts at 152-153°. The product melts at this same temperature after it has been kept for sixty hours in a vacuum desiccator, except that then there is no preliminary shrinking.
8. These directions are applicable equally well for runs of larger size.
9. The diethylamino homolog results when diethylamine hydrochloride is used.
3. Method of Preparation
The procedure described is an example of a general reaction,1'2 the Mannich reaction, a review of which, from the experimental point of view, has recently been published.3
1 Mannich and Heflner, Ber. 55, 359 (1922).
2 Blicke and Burckhalter, J. Am. Chem. Soc. 64, 453 (1942).
8 Blicke, Organic Reactions 1, 303 (1942), New York, John Wiley & Sons.
p-ETHOXYETHYL BROMIDE (Ethane, l-bromo-2-ethoxy-)
ÇÑãÍáÎÑÍãÑÍçÎÍ + PBr3 -+ ÇÑ2Í5ÎÑÍ2ÑÍ2ÂÃ + P(OH)3
Submitted by George C- Harrison and Harvey Diehl.
Checked by R. L. Shbiner and Ñ. H. Tilford.
In a 2-1. three-necked flask, fitted with a mechanical stirrer (Note 1), a reflux condenser, and a dropping funnel, is placed 630 g. (670 cc., 7 moles) of /Ç-ethoxyethyl alcohol (Note 2). The stirrer is started, and 600 g. (210 cc., 2.2 moles) (Note 3) of phosphorus tribromide is added from the dropping funnel over a period of one and one-half to two hours. The temperature is permitted to rise until the reaction mixture refluxes gently.
The mixture is then distilled, and the distillate boiling below 150° is collected in a 2-1. flask containing 11. of water. The lower layer of crude /Ç-ethoxyethyl bromide is separated and dried over
10 g. of calcium chloride. The liquid is decanted and distilled through a 25-cm. fractionating column, and the fraction boiling at 125-127°/760 mm. is collected (Note 4). The yield of pure product is 660-670 g. (65-66 per cent of the theoretical amount based on the phosphorus tribromide).
1. A rubber sleeve lubricated with a drop of oil provides an effective seal for the stirrer.
2. Technical /Ç-ethoxyethyl alcohol is marketed commercially as Cellosolve; it should be dried over calcium oxide and distilled.
3. A slight excess of /Ç-ethoxyethyl alcohol gives the best results.
4. The first fraction, boiling at 38-40°, is ethyl bromide, and it weighs 120-130 g. Lower yields (56-59 per cent) of /3-ethoxy-
ethyl bromide are obtained by distillation without a fractionating column. The residue, however, should not be overheated, for at high temperatures phosphorous acid decomposes to give phos-phine and perhaps even elementary phosphorus, and then, when air is admitted to the apparatus, an explosion may occur. A minor explosion in connection with this preparation has been reported (N. L. Drake, private communication), and a similar situation has been observed in reactions with phosphorus trichloride.1
3. Methods of Preparation
/Ç-Ethoxyethyl bromide has been prepared by the action of sodium ethoxide upon ethylene bromide; 2 by the action of bromine upon jS-ethoxyethyl iodide;3 and by the procedure adopted here, which was first used by Chalmers.4 The action of sodium bromide and sulfuric acid on /Ç-ethoxyethyl alcohol cleaves the ether linkage.
P-ETHOXYPROPIONITRILE (Propionitrile, p-ethoxy-)
Ñ2Í5ÎÑÍ2ÑÍ2ÂÃ + NaCN -> C2H5OCH2CH2CN + NaBr
Submitted by George C. Harrison and Harvey Diehl.
Checked by R. L. Shriner amd Ñ. H. Tilford.
In a 3-1. three-necked flask, equipped with a Hershberg stirrer (Org. Syn. 17, 31; Coll. Vol. 2, 1943, 117), a reflux condenser, and a dropping funnel, are placed 175 g. (3.6 moles) of sodium cyanide
1 Coghill, J. Am. Chem. Soc. 60, 488 (1938); see also Org. Syn. Coll. Vol. 3, 1943, Note 5, p. 40.