1,2-Dichloroethane → Hydrochloric Acid

Participants

Reaction Steps

A solution of 3-oxo-4-chlorobutyryl chloride was prepared by passing in 0.645 mols of Cl2 gas into a solution of 0.645 mol of diketene at -20°C in 1,2-dichloroethane which was approximately two-thirds solvent by volume. The starting diketene was of approximately 98.1 percent purity as assayed by NMR spectroscopy. The solution was then treated in a three neck flask fitted with thermometer, dropping funnel, condenser, mechanical stirrer and a N2 inlet and outlet with 11.8 ml of water (0.655 mol) added slowly from the dropping funnel. A slow stream of N2 gas was passed through the flask and allowed to pass out the condenser and into a NaOH solution prepared from 80 ml of 7.93 N NaOH (0.635 mol) diluted to approximately 800 ml. The water was added with vigorous stirring at such a rate that no HCl escaped the NaOH trap while maintaining a temperature of 25°-30°C in the reaction mixture. The product acid began to crystallize from the reaction mixture about one-third of the way through the addition of water. After completion of the addition, stirring was continued overnight. The NaOH trap solution was then made up to 1 liter and a 100 ml aliquot removed. This was titrated to a phenolphthalein end point requiring 3.23 ml of 0.1043 N HCl showing a net excess of 3.36 milliequivalents of unused base remained. This corresponds to a 99.8 percent yield of HCl based on diketene. The solid acid was recovered by filtration and yielded 61.1 g (70.8 percent of theory) of snow white crystalline product MP 69°-71°C. Further washing of the flask with pentane removed 1.32 g of solids. 21.3 g of acid was recovered upon evaporation of the residual solvent filtrate at room temperature on a rotary evaporator under vacuum. Both solid products were washed with pentane and found to be pure via their NMR spectra. The combined yield was 83.7 g or 97 percent of theory. The melting point reported by Rosdig, Kleppe and Markl is 67°-69°C (Ber. 95, 1252 (1962).

Provenance & Evidence