c 30 minutes refluxed for four hours and distilled to 124 u00b0 c 10 minutes the remainder of the hbr is removed when the mixture is cooled and concentrated on a rotary evaporator under vacuum at 6 mm pressure the resulting residue is dissolved in boiling etoh h 2 o 1175 ml 125 ml and allowed to crystallize at 4 u00b0 c for about 12 hours the crystals are collected by filtration washed with cold ethanol and then recrystallized from etoh h 2 o as described above the crystals are collected by filtration washed with cold etoh and dried in an oven under vacuum at 6 mm pressure at u02dc 60 u00b0 c for 12 hours the yield is approximately 254 4 g 78 of theoretical yield of white solid with a melting point of 170 171 u00b0 c this white powder is n 2 bromoethyl 1 2 ethanediamine dihydrobromide thin layer chromatography shows trace of a more polar impurity a higher percent yield of n 2 bromoethyl 1 2 ethanediamine dihydrobromide can be obtained by allowing the pot residue remaining after the final vigreux distillation to cool to 95 u00b0 c and then adding to this pot residue 100 ml of 100 ethanol n 2 bromoethyl 1 2 ethanediamine dihydrobromide will crystallize overnight the solid is collected and washed several times with ice cold 100 ethanol this yield is approximately 87 of theoretical yield the amount of hbr can be reduced to approximately 4 moles for every 1 mole of 2 2 aminoethylamino.