SYNTHESIS OF t-BUTYL CHLORIDE (2-Chloro-2-methylpropane)

• In a 250-ml separatory funnel place 25 g (0.34 mol) of 2-methylpropan-2-ol (t-butyl alcohol, b.p. 82-83 °C, m.p. 25 °C) and 85 ml of concentrated hydrochloric acid (1) and shake the mixture from time to time during 20 minutes. 

• After each shaking, loosen the stopper to relieve any internal pressure. 

• Allow the mixture to stand for a few minutes until the layers have separated sharply; draw off and discard the lower acid layer. 

• Wash the halide with 20 ml of 5 per cent sodium hydrogen carbonate solution and then with 20 ml of water. 

• Dry the preparation with 5 g of anhydrous calcium chloride or anhydrous calcium sulphate. 

• Decant the dried liquid through a funnel supporting a fluted filter paper into a 100-ml distilling flask, add 2-3 chips of porous porcelain and distil. 

• Collect the fraction boiling at 49-51 °C. 

• The yield of t-butyl chloride is 28 g (90%). The p.m.r. spectrum (CC1 4 , TMS) shows a signal at 5 1.67 (s, 9H, Me 3 C— ).

Notes to keep in mind:

1. The addition of 10 g of anhydrous calcium chloride tends to concentrate the acid and assists the separation of the chloride; the yield is slightly improved.

Cognate preparation: 2-Chloro-2-methylbutane

• Use 22 g (27 ml, 0.25 mol) of 2-methylbutan-2-ol (t-pentyl alcohol) and 65 ml of concentrated hydro- chloric acid. 

• Distil the chloride twice from a Claisen flask with fractionating side-arm or through a short column. Collect the 2-chloro-2-methylbutane at 83-85 °C; the yield is 18 g (68%). 

• Record the p.m.r. spectrum (CC1 4 , TMS) and assign the signals which appear at 5 1.01 (t, 3H), 1.51 (s, 6H) and 1.73 (q, 2H); note the overlap of the latter two signals.