Reaction XIX.— a Condensation of Anthranol Derivatives with Glycerol

Reaction XIX. (a) Condensation of Anthranol Derivatives with Glycerol. (B., 44, 1666.)—This condensation gives rise to the benz-anthrones which are used as intermediates in the dye industry. The reaction may be assumed to go as follows — 

Sulphuric acid is the condensing agent used. The reaction might be compared with the preceding reaction and with Skraup s quinoline synthesis (see p. 165). 

10 gms. (1 mol.) of anthranol are dissolved or suspended in 150 gms. of sulphuric acid (80%), and 10 gms. (excess) of glycerol are added. The mixture is carefully heated to 120°, when S02 is evolved, and kept there till the reaction is complete (4 hours). The cooled mass is poured into water, and the product which separates is collected, washed, boiled for 30 minutes with 13 times the quantity of 1% sodium hydroxide solution, pressed and dried. It is recrystallised from alcohol. 

Pale yellow needles insoluble in cold alcohol and in dilute acids and alkalis soluble in cone, sulphuric acid with a reddish-brown colour, and deep orange fluorescence M.P. 170°. (D.R.P. 176018 see also B., 44, 1666 O.S., XIV., 4 U.S.P., 1791309.) 

---