Purification of tetrahydrofuran

All precautions with regard to the purification of tetrahydrofuran, the quality of the iron powder, the rapid stirring, the maintenance of a nitrogen atmosphere, and the handling of cyclopentadiene, described in the preceding preparation, are followed. 

Propanol with magnesium in reduction of chlorobenzene, 47, 104 Propionyl fluoride, 46, 6 n Propylamine, 46, 85 n Propylhydrazine, 46, 85 C ( Propyl) N phenylmtrone, genera tion from phenylhydroxylamme and n butyraldehyde, 46, 97 Purification of tetrahydrofuran (Warning), 46,105 4H Pyran 4-one, 2 6 dimethyl 3,5 diphenyl, 47, 54... 

Tctrahydrofuran (purchased from Fluka AG or J. T. Baker Chemical Company) is distilled from sodium hydride prior to use. For warnings regarding the purification of tetrahydrofuran, see Org. Syn., Coll. Vol. 5, 976 (1973). 

Technical grade tetrahydrofuran was predried for a few days over sodium hydroxide. It was then heated under reflux over sodium wire with benzophenone until it developed a permanent blue color and distilled with exclusion of atmospheric moisture. [Caution See Org. Syntheses, 46, 105 1966), for a warning regarding purification of tetrahydrofuran.]... 

The ethylmagnesium bromide is prepared in dry tetrahydrofuran and stored no longer than 1 week in a 250-ml. tube fitted with a 3-way vacuum stopcock and a dropping buret. The solution is decanted into the buret, and the correct volume is transferred to the reaction flask with positive nitrogen pressure. The tetrahydrofuran is purified by distillation from lithium aluminium hydride. See Org. Syn., 46, 105 (1966), for warning regarding the purification of tetrahydrofuran. 

Tetrahydrofuran is dried by distillation from lithium aluminum hydride. (See Org. Syn., 46, 105 (1966) for warning note regarding the purification of tetrahydrofuran.)... 

The checkers used reagent-grade tetrahydrofuran (available from Fisher Scientific Company) from a freshly opened bottle. The submitters used tetrahydrofuran purified as described in L. F. Fieser, Experiments in Organic Chemistry, 3rd ed., Revised, D. C. Heath and Co., Boston, 1957, p. 292. (See Org. Syn., 46, 105 (1966) for a warning regarding the purification of tetrahydrofuran.)... 

It has been reported that serious explosions may occur when impure tetrahydrofuran is treated with solid potassium hydroxide or with concentrated aqueous potassium hydroxide, as has been recommended widely for the purification of tetrahydrofuran see Org. Syntheses, Coll. Vol. 4,474, 792 (1963) Vol. 40,94 (1960). There is evidence that the presence of peroxides in the tetrahydrofuran being purified was causal. It is strongly recommended, therefore, that this method not be used to dry tetrahydrofuran, if the presence of peroxides is indicated by a qualitative or quantitative test with acidic aqueous iodide solution. Traces of peroxide can be removed by treatment with cuprous chloride sec Org. Syntheses, 46, 57 (1965). The safety of this operation should be checked first on a small scale (1-5 ml.). It is recommended that tetrahydrofuran containing larger than trace amounts of peroxides be discarded by flushing down a drain with tap water. It must be kept in mind that mixtures of tetrahydrofuran vapor and air are easily ignitable and explosive purification is best carried out in a hood which is well exhausted and which does not contain an ignition source... 

Details for the purification of tetrahydrofuran are given in Inorganic Syntheses, 12, S17 (1970). 

Tetrahydrofuran (THF) was distilled from lithium aluminum hydride under nitrogen (Caution See Org. Synth., Coll., Vol. V1973, 976 for a warning regarding the purification of tetrahydrofuran. The checkers employed THF that had been purified by distillation from sodium and benzophenone.). 

Reagent grade tetrahydrofuran available from Fisher Scientific Company was used by the checkers. For warning regarding the purification of tetrahydrofuran see Org. Syntheses, 46, 105 (1966). 

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