In a 2-l. three-necked round-bottomed flask, equipped with a sealed stirrer, dropping funnel, and a reflux condenser topped by a calcium chloride tube, is placed 440 g. (6 moles) of dimethylformamide (Note 1). While the flask is carefully cooled in an ice bath, 253 g. (1.65 moles) of phosphorus oxychloride is added dropwise with stirring. An exothermic reaction occurs with the formation of the phosphorus oxychloride-dimethylformamide complex. When all the phosphorus oxychloride has been added, and the heat of the reaction has subsided, 200 g. (1.65 moles) of dimethylaniline (Note 2) is added dropwise with stirring. When the addition of the dimethylaniline is complete, a yellow-green precipitate begins to form. The reaction mixture is heated on a steam bath, and stirring is continued for 2 hours. The yellow-green precipitate redissolves when heating is begun. The mixture is then cooled and poured over 1.5 kg. of crushed ice in a 5-l. beaker. Any precipitate that remains in the flask may be washed into the ice mixture with cold water. The solution is neutralized to pH 6–8 (Universal Test Paper) by the dropwise addition of approximately 1.5 l. of saturated aqueous sodium acetate with vigorous stirring (Note 3). p-Dimethylaminobenzaldehyde begins to precipitate soon after the addition of the sodium acetate is begun. The neutral mixture (total volume about 4.5 l.) is stored in the refrigerator overnight (Note 4). The greenish-tinted crystalline precipitate is filtered by suction, with the aid of a rubber dam, and washed several times with water on the filter. The green color is readily removed during the washing. The very light-yellow to nearly colorless product, after air-drying, weighs 198–208 g. (80–84%) and melts at 73–74°. It is essentially pure and useful for most purposes as obtained (Note 5).