Goal: To prepare 1-Bromobutane by the SN2 reaction from 1-Butanol with Sodium Bromide and Sulfuric Acid. Mechanism:
1.Place 27g of NaBr, 20mL of n-butyl alcohol, and 30mL of water into a 250mL round bottom flask. 2.Put the mixture in an ice-water batch and cool briefly, then slowly add 23 mL of conc H2SO4 while stirring with a magnetic stirrer. 3.Place a water-cooled condenser and heat the flask until the mixture boils while still stirring with a magnetic stirrer. (note the time and adjust the hot plate to maintain a brisk, steady reflux with vigorous stirring) 4.The upper layer that separates is the alkyl bromide (because the aqueous soln of inorganic salts has a higher density. 5.Reflux for 50 mins and then cool to room temp.
6.Remove the condenser and set up a steam distillation apparatus with a 100-mL round bottom flask as a receiver. 7.Add 50mL of water and distill the mixture (add water if necessary to keep volume constant. 8.Pour the distillate into a separate funnel and add 20mL of water stopper and then shake. (the butyl bromide layer is the LOWER layer) 9.Decant the lower layer into a fresh Erlenmeyer flask.
10.Clean and dry the separatory funnel and place the butyl bromide into it. 11.Thoroughly cool 20ml of conc H2SO4 in an ice bath and add to funnel. . 12.Shake carefully and VENT.
13.Separate the layers and test for the organic layer.
14.Wash the butyl bromide with 20mL of 10% of sodium hydroxide solution to remove traces of acid. 15.Separate and wash with 15mL of saturated salt solution
16.Dry the cloudy butyl bromide by adding a few grams of calcium chloride and stir in an ice bath for a few minutes. 17.Decant the dried liquid into a 25mL round bottom flask and preform simple distillation collecting the distillate at 99-103°C. (yield should be around 6-10 g)