Sulfuric Acid → I2-Ionone

Participants

Reaction Steps

The cyclizing agent [35 g of conc. sulfuric acid (95%) and 15 g of glacial acetic acid] was placed in a 250 ml three-necked flask with a mechanical stirrer, a dropping funnel, and a thermometer reaching into the reaction mixture. The flask was cooled in an ice bath and the cyclizing agent was vigorously stirred while pseudoionone (10 g ) was added dropwise during 15-20 minutes; the rate of addition was adjusted so that the temperature of the reaction mixture did not exceed 10° C. After addition, the cooling bath was removed and stirring was continued at 10°-15° C. for 5-10 minutes. The reaction mixture was poured into a mixture of ice and water (200 g) and ether (100 ml) with vigorous stirring. The water layer was again extracted with ether and the combined ether extracts were washed with water, sodium carbonate solution (1%), then to neutral with water and dried over anhydrous magnesium sulphate. After the removal of ether, the residue was distilled under reduced pressure. β-Ionone (5.1 g) was obtained as a pleasant smelling light yellow colored liquid; boiling point 73° C./0.25 mm; nD25 1.5164.

Provenance & Evidence