A
5-l. round-bottomed three-necked flask is equipped with a
mechanical stirrer in a suitable seal (Note
1), a
reflux condenser of the cold-finger type (Note
2) protected from moisture in the air by a drying tube, and a
gas delivery tube extending nearly to the bottom of the flask. The flask is surrounded by an
ice bath, and the cold finger is filled with solid
carbon dioxide in acetone. Approximately
1.7 l. of dry ether and
61 g. (2.5 gram atoms) of magnesium are placed in the flask and cooled to about 0°.
Methyl chloride (130 ml., 130 g., 2.6 moles) is condensed (Note
3) in a
250- to 300-ml. test tube held in a bath of solid
carbon dioxide in
acetone (Note
4). About
50 ml. of methyl chloride is allowed to distil from the test tube containing the
methyl chloride through the gas delivery tube into the rapidly stirred mixture of
ether and
magnesium. The reaction mixture is then warmed until the reaction of
methyl chloride and
magnesium is under way. A crystal of
iodine may be added if the reaction does not start readily. The
methyl chloride is then allowed to distil into the reaction mixture during a period of about 3 hours. The reaction mixture and the tube containing the
methyl chloride are cooled if the refluxing of the reaction mixture becomes so vigorous that the reflux condenser does not condense the
methyl chloride. After all the
methyl chloride has been added, the reaction mixture is warmed for 1 hour so that there is a gentle reflux.
At the end of this time, when almost all the
magnesium has reacted, the Dry Ice cold finger is replaced with a water condenser and the gas delivery tube with a
dropping funnel. A solution of
142 g. (2.02 moles) of freshly distilled crotonaldehyde in 300 ml. of dry ether is added dropwise while the reaction mixture is stirred vigorously and cooled. The reaction mixture is allowed to stand at room temperature for 1 hour.
The Grignard addition compound is decomposed by adding
435 ml. of a saturated ammonium chloride solution (Note
5) dropwise, with vigorous stirring, to the thoroughly cooled reaction mixture. A dense white precipitate, too heavy to be stirred mechanically, forms and settles to the bottom of the flask. After the reaction mixture has been allowed to stand for 1 hour, the
ether solution is poured off and the precipitate washed by decantation with two
300-ml. portions of ether.
The
ether is removed by distillation, and the residual
3-penten-2-ol is distilled through a short column (Note
6) at atmospheric pressure. The yield of material boiling at
119–121° is
140–150 g. (
81–86%). Pure
3-penten-2-ol boils at approximately
120°/740 mm.