Question

To synthesize butane from isobutyl bromide

Answer 1

Answer:

Isobutyl bromide:-

With cooling, 1 mole of the tert-butyl alcohol is treated with 1.25 mole of hydrogen bromide (in the form of the 48%, constant-boiling, acid), and the obtained mixture is boiled and volatile tert-butyl bromide is distilled out from the reaction mixture directly (20-cm Vigreux column, vertical condenser, rate of distillation 2 to 3 drops per second). The obtained crude tert-butyl bromide is twice shaken carefully with about one-fifth of its volume of cold concentrated sulfuric acid or the same volume of concentrated hydrochloric acid in the separating funnel to dissolve the ether produced as a by-product. Then crude tert-butyl bromide is washed with water then it is freed from acid with sodium bicarbonate solution, washed again with water, dried over calcium chloride, and distilled through a 20-cm Vigreux column. The yield of isobutyl bromide is 60%, n20/D 1.4279; mp.p −20 °C; b.p. 71-73 °C; 1.22 g/mL at 20 °C. tert-Butyl bromide should contain 0.5% potassium carbonate as stabilizer.

Organicum. Practical Handbook of Organic Chemistry, by Heinz Becker, Werner Berger and Günter Domschke, Addison-Wesley Pub. Co, 195-196, (1973)

Alternatively, 1.6 moles of tert-butyl alcohol are added dropwise with stirring to a cooled mixture of 3.2 moles of 48 % hydrogen bromide and 100 ml of concentrated sulfuric acid at 20°C. The crude tert-butyl alcohol is separated after 30 min, washed twice with water, and dried with calcium chloride and a little calcium oxide, thus yielding 85% of tert-butyl bromide together with a little isobutene.

Explanation: