Cyclomethyhexnene Synthesis

This experiment consisted of the formation n-butyl bromide from 1-butanol and sodium bromide under SN2 conditions. In theory, the bromine atom, a strong nucleophile, must attack the protonated alcohol and displace water, which becomes a better leaving group than the original –OH. Because of the primary carbon of 1-butanol, the bromide anion backside attacked which led to a transition state, followed by a change in stereochemistry, forming n-butyl bromide.

While preparing the n-butyl bromide, 17.0 grams of NaBr, 17mL of water, and 10.0 mL of 1-butanol was added into a flask. The lab manual says that the mixture must be in an ice bath, and the sulfuric acid must be added slowly. Unfortunately, this part of the experiment had to be repeated, because we failed to reread the instructions. The addition of the starting materials produced an exothermic reaction, which is why the ice was used and the mixture had to be constantly swirled. The sulfuric acid was added produced a significant amount of heat, enough to create a cloud inside of the flask, and even a light smoke that escaped the flask. It was necessary to add the sulfuric acid slowly, since too much of the acid at once would result in the oxidation of sodium bromide, which would later not be useful because it would not be a nucleophile.

The mixture was then set on a reflux apparatus for about 65 minutes. After the refluxing, the mixture separated into two layers; the top layer being the akyl bromide. The mixture became distilled, which allowed the two liquids to become distinct of one another, and separate due to differences in density and boiling points. Although the two layers were separated, the organic layer still contained water, unreacted 1-butanol, and sulfuric acid. The organic layer (n-butyl bromide) was a colorless and cloudy liquid. It was immiscible with water but miscible in alcohol.

Later, more sulfuric acid was added to remove the by-products, (n-butyl ether, 1-butene, unreacted starting...