The Generation of Sodium Acetylide in Tetrahydrofuran

The problems of handling liquid ammonia are alleviated in this modification of the sodium acetylide generation procedure. Finely divided sodium is prepared in boiling toluene, the toluene is replaced by THF, and a direct reaction between sodium and acetylene is carried out. The resulting sodium acetylide is employed in ethynylation reactions as before. 

Reaction with Alkyl Halides The gas inlet tube is replaced by an addition funnel, and 10 ml of HMPT is added rapidly with stirring. The mixture is cooled to 10-15°, and a solution of the alkyl halide (0.1 mole) in 20 ml of THF is added dropwise over a period of 30-40 minutes. The mixture is then heated to 40° for 2-3 hours. The thick white suspension of the sodium halide is cooled and dilute cold hydrochloric acid is carefully added until the mixture is clear. The organic layer is separated, and the aqueous layer is extracted three times with 20-ml portions of ether, the ethereal extracts then being combined with the organic material. The ethereal solution is washed twice with saturated sodium chloride solution and dried. The ether and THF are removed under reduced pressure (rotary evaporator), and the alkyne is distilled. 

1-Heptyne, bp99-100°, Wd 1.4084, is obtained in 57% yield from 1-bromopentane. 

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