1,3,5-Hexatriene (CAS NO.: ), which is also known as hexatriene, could be produced through the following synthesis routes.

A. 1,5-Hexadien-3-ol. In a 5-l. three-necked flask fitted with a stirrer, a dropping funnel and an ice-water condenser are placed 153.0 g. (6.28 g. atoms) of magnesium turnings, 360 ml. of anhydrous ether, and a few crystals of iodine. A solution of 351.0 g. (2.90 moles) of allyl bromide in 2.6 l. of ether is added in small portions until the reaction begins, and then at such a rate as to maintain gentle refluxing of the ether. The addition requires about 3 hours, after which the reaction mixture is refluxed on a steam bath for an additional hour. (104.0 g., 1.86 moles) is added during 2 hours, and this causes gentle refluxing. After an additional hour at room temperature the reaction mixture is poured slowly into 2 l. of ice water. The precipitate is dissolved by adding slowly a solution of 120 ml. of concentrated sulfuric acid (sp. gr. 1.84) in 400 ml. of water. The organic layer is separated and the water layer extracted with three 200-ml. portions of ether. The combined oil and ether extracts are dried over 8–10 g. of anhydrous magnesium sulfate. After removal of the ether, the residue is distilled through a 6-in. column packed with glass helices to yield 104–108 g. (57–59%, based on acrolein) of 1,5-hexadien-3-ol; b.p. 62–65/50 mm., n_D25 1.4440.

B. 1,3,5-Hexatriene. In a 500-ml., three-necked, round-bottomed flask fitted with a mechanical stirrer, a thermometer, and a graduated dropping funnel are placed 114 g. (0.42 mole) of phosphorus tribromide and 2 drops of 48% hydrobromic acid. As the contents of the flask are stirred and maintained at 10–15° by means of an ice-water bath, 98 g. (1.00 mole) of 1,5-hexadien-3-ol is added in the course of 1.5 to 1.75 hours. The mixture is allowed to stir at 10–15° for 40 minutes and then to stand at room temperature overnight. The flask is cooled in an ice-salt bath for 20 minutes, and the upper organic layer is decanted from the residue while still cold. The organic layer is successively washed with three 40-ml. portions each of ice water, 5% sodium bicarbonate, and water. The crude bromohexadiene weighs 147–153 g. (91–95%).

In an assembly similar to that used for the previous reaction, 90 g. (0.67 mole) of dimethylbenzylamine, 0.13 g. of hydroquinone, and 500 ml. of water are stirred and heated at 50°. The crude bromohexadiene (107 g., 0.67 mole) is added in the course of 20–40 minutes, and stirring and heating are maintained at 50° for 2–2.5 more hours. The flask is then fitted for downward distillation, and the mixture is distilled at about 40–50° and 30 mm. until no more oil distils with the water. A total of 133–200 ml. of distillate is collected. This is discarded.

A solution of sodium hydroxide (106 g., 2.7 moles) in 535 ml. of water is placed in a 2-l. flask equipped with a sealed mechanical stirrer and an outlet arranged for downward distillation into an ice-cooled receiver. The aqueous solution of the quaternary bromide is added dropwise to the boiling solution of sodium hydroxide during a period of 2.5–4 hours. The hexatriene and dimethylbenzylamine which form are distilled with the water. Distillation is continued for 10–15 minutes after the final addition of quaternary bromide solution. The clear upper layer of the distillate is separated, cooled to 5–10°, washed with three 170-ml. portions each of cold 2N hydrochloric acid and water, and dried over anhydrous sodium sulfate. The oil is then distilled, a spinning-band column being used to give 32.0–34.0 g.. (54–60%) of 1,3,5-hexatriene; b.p. 80–80.5°, n_D20 1.5103–1.5119.