Preparation of tri-n-heptyl carbinol
For the preparation of Grignard reagent, the apparatus and reagents must be perfectly dry. 36 grams of dry magnesium turnings and 275 ml of anhydrous ether are placed in a 1-liter three-necked flask. The reaction is commenced by adding 5.9 ml (or 8.6 grams) of dry 1-bromoheptane through the dropping funnel without stirring. A solution of 179.3 ml (or 260 grams) of 1-bromoheptane in 350 ml of anhydrous ether are introduced while stirring at such a rate that the mixture refluxes gently. The addition occupies about 45 minutes and the flask is cooled externally during the addition if necessary. After the 1-bBromoheptane solution in the ether has been added, the stirring is continued for a further 15 minutes. Then a solution of 53.5 ml (or 52 grams) of pure diethyl carbonate in 70 ml of anhydrous ether are dropwise added, with rapid stirring, over a period of about one hour. (Diethyl carbonate for the preparation of tri-n-heptyl carbinol may be purified by the following process. 100 ml of diethyl carbonate are washed with 20 ml of 10% sodium carbonate solution, 20 ml of saturated calcium chloride solution, and 25 ml of water. Diethyl carbonate is left for one hour over anhydrous calcium chloride with occasional shaking, then filtered into a dry flask containing 5 grams of the same desiccant, and allowing to stand for a further hour. The dried diethyl carbonate is distilled the fraction boiling at 125-126° C is collected.) A vigorous reaction sets in and the ether refluxes continually. When the diethyl carbonate has been added, the reaction flask is heated on a water bath with stirring for another hour. The reaction mixture is poured, with frequent shaking, into a 2-liter round-bottomed flask containing 500 grams of crushed ice and a solution of 100 grams of ammonium chloride in 200 ml of water, which is transferred to a separatory funnel. The ether layer is removed, and the aqueous solution is extracted with ether. The combined ethereal extracts are dried with anhydrous potassium carbonate or with anhydrous calcium sulfate, and the ether is removed by evaporation. The crude tri-n-heptyl carbinol is fractionated through a short column, collecting the fraction boiling at 195–200° C/6 mm. The yield of tri-n-heptyl carbinol is 75-80%.
Org. Synth. 1931, 11, 98