AUTOXIOATION OF BENZOIN Submitted by: Philip S. Chen, Atlantic Union College, South Lancaster, Mass. 01561
Tested by: Adele Hoskin, Hiram College, Hiram, Ohio 44234
PREPARATION
REMARKS
Two beakers, 250 ml. Dissolve 0.8 g benzoin in 100 ml methyl alcohol. Dissolve 2 g KOH in 4 ml water and allow the solution to cool to room temperature.
Benzoin, C6H5COCHOHC8HS,in its enediol form undergoes autoxidation in alkaline solution in the presence of air. The oxidation product benzil, CBH5COCOC,H,, which itself is colorless, is believed to combine withbenzoin and alkali to form the colored complex. This complex is very sensitive to oxidation and turns to straw yellow when. shaken with air.'
DEMONSTRATION
Pour the two solutions together. After a short induction period the solution acquires a violet color. On pouring i h e solution from one beaker to the other the violet color changes to a light straw color. The violet color reappears on standing. The cycle of changes may be repeated a number of times.
~FIESER, L. F. and Fieser, M., "Organic Chemistry," (3rd ed.), Reinhold Publishing Co., New York, 1965, p. 694.
Volume 47, Number
I , Jonuory 1970
/
A67
