Precursor for 2C-E, etc.
One drop of concentrated sulfuric acid is added to a mixture of 110 g. (1.0 mole) of hydroquinone and 206 g. (190.3 ml., 2.02 moles) of acetic anhydride (Note 1) in a 1 L Erlenmeyer flask. The mixture is stirred gently by hand; it warms up very rapidly, and the hydroquinone dissolves. After 5 minutes the clear solution is poured onto about 800 ml. of crushed ice. The white crystalline solid which separates is collected on a Buchner filter and washed with 1 L of water. The filter cake is pressed occasionally to facilitate the removal of water; the solid is dried to constant weight over phosphorus pentoxide in a vacuum desiccator. The nearly pure product weighs 186-190 g. (96-98%) and melts at 121-122Â°C (Note 2); it can be recrystallized from dilute ethanol (Note 3).
A mixture of 50g (0.257 mole) of dry hydroquinone diacetate and 116g (0.87 mole) (Note 1) of anhydrous aluminum chloride is finely powdered in a mortar and introduced into a dry 500-mL RB flask fitted with an air condenser protected by a calcium chloride tube and connected to a gas-absorption trap. The flask is placed in an oil bath (Note 2) which is heated slowly from room temperature so that at the end of about 30 minutes the temperature of the oil reaches 110-120°C, at which point the evolution of hydrogen chloride begins. The temperature is then raised slowly to 160-165°C and maintained at that point for about 3 hours (Note 3); at the end of about 2 hours the evolution of hydrogen chloride becomes very slow and the mass assumes a green color and becomes pasty in consistency (Note 4).
The flask is removed from the oil bath and allowed to cool to room temperature. The excess aluminum chloride is decomposed by treating the reaction mixture with 350g of crushed ice followed by 25mL of concentrated hydrochloric acid. The solid obtained is collected on a BÃ¼chner funnel and washed with two 100mL portions of cold water. The crude product weighs about 35g (89-90%). Recrystallization from 4L of water yields 25-30g (64-77%) of green, silky needles melting at 202-203°C (Note 5).