A mixture of
312 g. (3 moles) of acetone dimethyl acetal (Note
1),
489 g. (6.6 moles) of butanol,
1.0 l. of benzene, and
0.2 g. of p-toluenesulfonic acid is placed in a
3-l. flask. The flask is connected to a packed
fractionating column and the solution distilled until the azeotrope of
benzene and
methanol, boiling at 58°, is completely removed (Note
2). The contents of the boiler are then cooled below the boiling point and a solution of
0.5 g. of sodium methoxide in
20 ml. of methanol (Note
3) is added all at once with stirring. The flask is replaced for further distillation, and most of the remaining
benzene is distilled at atmospheric pressure. The pressure is then reduced, and the remaining
benzene and unreacted
butanol are removed (Note
4). Finally, the pressure is reduced to 20 mm., the last traces of low-boiling materials are taken to the cold
trap, and the product is distilled. After a small fore-run,
acetone dibutyl acetal is collected at 88–90°/20 mm. The yield is
421–453 g. (
74.6–80.3%),
n25D 1.4105,
d254 0.8315.