Checked by V. Boekelheide and H. Kaempfen.
1. Procedure
A
2-l. flask containing
1.0 l. of anhydrous ether (Note
1) is fitted with a
stopper bearing an inlet tube dipping below the surface of the
ether and an outlet tube protected by a
calcium chloride drying tube. After the
ether has been cooled thoroughly in an
ice-salt bath, the flask is placed on a balance and
cold methyl bromide (Note 2) is introduced through the inlet tube until the gain in weight is 200 g. (2.1 moles).
In a
3-l. three-necked flask, equipped with a sealed mechanical stirrer, reflux condenser, and a pressure-equalizing separatory funnel (Note
3), are placed
48 g. (2 g. atoms) of magnesium turnings,
500 ml. of anhydrous ether, and a small crystal of
iodine. The cold
methyl bromide solution is transferred to the
separatory funnel and slowly added, with stirring. The reaction starts spontaneously, and the remainder of the
methyl bromide is added at a rate such that the solution boils gently under reflux. Generally, the addition is complete at the end of 1–2 hours and all the
magnesium should be dissolved. After the stirred solution of
methylmagnesium bromide is well cooled by using an
ice bath, a solution of
78.0 g. (0.5 mole) of γ-nonanoic lactone (Note
4) in
100 ml. of dry ether is added slowly over a period of 30 minutes. When the addition is complete, the mixture is placed on a
steam bath and boiled under reflux for 2 hours. Then the condenser is arranged for downward distillation (Note
5), and the
ether is removed.
To the thick, syrupy residue is added
200 ml. of benzene, and, after the solution is cooled in an ice bath and the condenser is set for reflux, 350 ml. of water is slowly added through the separatory funnel, with stirring. This is followed by the cautious addition of
325 ml. of a 20% solution of hydrochloric acid, and stirring is continued untill all the precipitate dissolves. The organic layer is then separated, and the aqueous layer and flask are washed with
50 ml. benzene. The combined
benzene extracts are washed successively with water, a
5% solution of sodium carbonate, and again with water. Concentration of the
benzene solution gives
88.5 g. of an oily residue. Careful fractional distillation (Note
6) of this residue gives, after a fore-run,
53.0 g. (
57%) of the pure
2-methyl-2,5-decanediol boiling at
65–69°/2 mm.,
n25D 1.4420.
2. Notes
2. Commercial
methyl bromide (Eastman Kodak Company, Rochester, New York) was used without purification.
3. The separatory funnel is fitted to an adapter tube extending to the bottom of the flask so that the
methyl bromide solution is introduced below the surface of the mixture. A drying tube is placed in the condenser outlet.
4.
Commercial γ-nonanoic lactone (Aldrich Chemical Co., Milwaukee, Wisconsin) was purified by distillation prior to use. The refractive index of the pure lactone is
n25D 1.4449.
5. As the removal of
ether proceeds, the viscous solution becomes difficult to stir and stirring may be stopped without harm.
6. The checkers found that an
ordinary Vigreux column wasineffective in separating lower-boiling impurities. An
efficient fractionating column 1m. in length and of 5 mm. I.D. gave excellent results. The infrared spectrum of the product gave no evidence of impurities.
3. Discussion
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