Competitive Nucleophiles

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Katie Smith
April 11, 2013

Competitive Nucleophiles
The purpose of this experiment was to compare the nucleophilicities of chloride and bromide ions toward the n-butyl and t-pentyl alcohols. We were able to analyze this by using refractometry to measure the amounts of alkyl chloride and alkyl bromide in each reaction.

Experiment Scheme
(Procedure A)
To begin the experiment, we assembled a reflux apparatus in the fume hood with a 100 mL round bottom flask and a condenser. Next we added 44 mL of sulfuric acid to a 125 mL Erlenmeyer flask. We also measured 4.75g ammonium chloride and 8.75g ammonium bromide into a 125 mL beaker, crushed the lumps, and placed in a 250 mL Erlenmeyer flask along with the sulfuric acid. We used heat to help the solutes dissolve. When they had dissolved, we allowed the flask to cool and then poured 17 mL of the solution into a separatory funnel and the rest of the solution into the reflux apparatus. 2.5 mL of 1-butanol was added to the reflux apparatus along with a boiling stone. We then started the circulation of water and brought the mixture to a gentle boil for 75 minutes. After that time we allowed it to cool in an ice bath. We then transferred the solution to a 125 mL separatory funnel and allowed the phases to separate. The lower layer was drained and the halide solution was decanted into a ground-glass stoppered flask. We then analyzed the sample using refractometry. (Procedure B)

We measured 2.5 mL if 2-methyl-2-butanol into the separatory funnel containing the other portion of solvent-nucleophile medium. To mix, we replaced the stopper and swirled, inverted, and released the pressure multiple times. The layers were allowed to separate and the lower layer was drained along with another small portion to eliminate any contamination. The remaining alkyl halide was drained into a beaker containing 0.5g of sodium bicarbonate and decanted into a ground glass stoppered flask. This sample was then...
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