SYNTHESIS OF BUTYL CHLORIDE (1 -Chlorobutane)

• Fit a 250-ml round-bottomed flask with a reflux condenser, the top of which is connected to a device for absorbing hydrogen chloride. 

• Place 68 g (0.5 mol) of anhydrous zinc chloride and 40 ml (47.5 g) of concentrated hydrochloric acid in the flask, add 18.5 g (23 ml, 0.25 mol) of butan-1-ol and reflux the mixture gently for 2 hours. 

• Arrange the condenser for downward distillation, and distil the reaction product, collecting the material which boils below 1 15 °C. 

• Separate the upper layer of the distillate, mix it with an equal volume of concentrated sulphuric acid (1) and transfer the mixture to a 250-ml flask fitted with a reflux condenser. Reflux gently for 15-30 minutes, and then distil the chloride from the acid; it will pass over at 76-79 °C. 

• Wash the distillate successively with 25 ml of water, 10 ml of 5 per cent sodium hydroxide solution and 25 ml of water; dry over 1-2 g of anhydrous calcium chloride, filter and distil from a small distilling flask. Collect the butyl chloride at 75-78 °C. The yield is 15-16g (65-69%). 

• The p.m.r. spectrum (CC1 4 , TMS) shows signals at (50.95 (t, 3H, Me), 1.10-2.00 (m, 4H, — CH 2 -CH 2 — ) and 3.49 (t, 2H, — CH 2 C1). The base peak in the m.s. appears at m/z 56 (M - HC1).

Notes to keep in mind: 

1. The sulphuric acid treatment removes high-boiling impurities which are not

easily separated by distillation.

Cognate preparations:

• The following alkyl chlorides may be prepared in sim- ilar yield by replacing the butan-1-ol in the above preparation by the appro- priate quantity of the requisite alcohol: 1 -chloropentane, b.p. 104-107 °C, from 22 g of pentan-1-ol; l-chloro-3-methylbutane, b.p. 98-100 °C, from 22 g of 3-methylbutan-l-ol (isopentyl alcohol); 2-chlorobutane, b.p. 67-69 °C, from 18.5 g of butan-2-ol.