Experiment 14: Preparation of 1-Bromobutane
Goal: To prepare 1-Bromobutane by the SN2 reaction from 1-Butanol with Sodium Bromide and Sulfuric Acid. Mechanism:
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.
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.
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.
Separate the layers and test for the organic layer.
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
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)
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