Propylamine → N-Butyl-N'-propylurea

205.8 Grams (3.48 moles) of n-propylamine and 250 ml of dichloromethane were charged to a round bottom flask equipped with stirrer, thermometer, reflux condenser and dropping funnel. 313.7 Grams (3.16 moles) of butyl isocyanate were added to the dropping funnel and then metered into the flask with stirring and strong external cooling (solid CO2 bath) at a rate slow enough to maintain the contents generally below 0° C. except for brief excursions to higher temperatures. The resulting mixture was left to stand overnight and then freed of solvent and lights under vacuum with a rotary evaporator leaving 462.3 g of crude product (92.6% crude yield). After further drying of a portion under vacuum a 97.6 area % purity was recorded by gas chromatography. The product contained substantially only one compound by gas chromatography. It melted at 70°-72° C.