Pentamethylene bromide (CAS NO.: ), with other names like 1,5-dibromopentane, could be produced through the following synthetic methods.

A hydrobromic acid solution is prepared in a 500-ml. round-bottomed flask by passing sulfur dioxide into a mixture of 120 g. (37.7 ml., 0.75 mole) of bromine, 50 ml. of water, and 150 g. of crushed ice. This is equivalent to a mixture of 253 g. (1.5 moles) of 48% hydrobromic acid and 74 g. of concentrated sulfuric acid. To the mixture 21.5 g. (0.25 mole) of tetrahydropyran (p. 794) is added, a reflux condenser is attached to the flask, and the light-brown homogeneous mixture is refluxed for 3 hours.

The heavy lower layer is separated, washed once with a saturated solution of sodium bicarbonate and once with water, and then dried over 4–5 g. of anhydrous calcium chloride. The crude product is decanted from the calcium chloride, and the drying agent is rinsed once or twice with a small quantity of ethyl bromide which is added to the main product. The mixture is distilled under reduced pressure, and the pentamethylene bromide, which weighs 46–47 g. (80–82%), is collected at 104–106°/19 mm.