In a
600-ml. beaker,
80 g. of polyphosphoric acid (Note
1) is warmed on a
steam bath to 90°. There is then added in one lot, with manual stirring,
22.0 g. (0.134 mole) of molten γ-phenylbutyric acid (Note
2), previously warmed to 65–70°. The mixture is removed from the steam bath and is stirred steadily by hand for 3 minutes; during this time a temperature of 90° or slightly higher is maintained by the heat of the reaction. An additional
70 g. of polyphosphoric acid is then added, and the mixture is again warmed on a steam bath for 4 minutes while being stirred vigorously by hand. The resulting solution is allowed to cool to 60°, and is hydrolyzed by addition to 200 g. of ice and water.
When the hydrolysis is complete, as indicated by the disappearance of orange, viscous material and the appearance in its stead of yellow oil, the aqueous mixture is transferred to a
500-ml. separatory funnel and extracted with two portions of
ether, 200 ml. and 100 ml., respectively. The extracts are combined and washed successively with 200 ml. of water, two
100-ml. portions of 5% sodium hydroxide solution (Note
3), 200 ml. of water,
100 ml. of 3% aqueous acetic acid,
100 ml. of 5% sodium bicarbonate solution, and 100 ml. of water. The
ether solution is dried over anhydrous
magnesium sulfate. The
ether is removed either by evaporation on a steam bath or by distillation from a
50-ml. flask into which the solution is introduced continuously, as fast as the solvent is distilled, by means of a
dropping funnel reaching below the side arm of the distilling head. The flask is fitted with a
6-in. Vigreux column, and the residual oil is distilled under reduced pressure. There is obtained
14.8–16.9 g. (
75–86%) of colorless oil, b.p.
90–91°/0.5–0.7 mm. or
94–95°/2.1–2.3 mm. (Note
4).