Hydrochloric Acid → 2-Chloro-5-(trifluoromethyl)benzaldehyde

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Reaction Steps

3-Amino-4-chlorobenzotrifluoride (A.E. Porai-Kosic et al., Zh. Prikl. Khim. 28, 969, 1955; Chem. Abstr. 50, 4880, 1956) (222 g) is slowly added to a stirred solution of 260 ml hydrochloric acid in 2330 ml water. The resultant suspension of the hydrochloride is cooled, treated with 450 g of ice and diazotized at 0°-5° C. with a solution of 80 g of sodium nitrite in 110 ml of water, added dropwise. The mixture is stirred for 1 hour at 0°-5° C. and treated with a cooled solution of 100 g of sodium acetate trihydrate in 150 ml water. The undissolved substance is separated (distillation recovers 70.8 g starting 3-amino-4-chlorobenzotrifluoride) and the solution of the diazonium salt is added while stirring at 10°-20° C. to a solution of formaldoxime (prepared by boiling a mixture of 57.5 g paraformaldehyde, 131.5 g of hydroxylamine hydrochloride, 255 g of sodium acetate trihydrate and 850 ml of water for 15 minutes) and a solution of 32.5 g cupric sulfate pentahydrate, 5 g sodium of sulfite and 800 g of sodium acetate in 300 ml water with the addition of 300 ml of toluene. The mixture is stirred for 2 hours, 1100 ml of hydrochloric acid added and the mixture refluxed for 2 hours. It is then distilled with steam and the distillate extracted with benzene. The extract is washed with a 5% sodium hydrogen carbonate solution and evaporated. The residue is dissolved in 200 ml ether and the solution stirred for 2 hours with 450 ml of 40% sodium hydrogen sulfite solution. After standing overnight, the precipitated addition product is filtered with suction, washed with ether, and suspended in 1 liter of water, then, 200 ml of hydrochloric acid are added and the mixture refluxed for 2 hours. After cooling, it is extracted with benzene, the extract dried with magnesium sulfate, evaporated and the residue processed by distillation. There are obtained 49.1 g (31% per conversion) of 2-chloro-5-trifluoromethylbenzaldehyde, b.p. 93°-96° C./2.1 kPa.

Provenance & Evidence