Reaction of Butanols with Hydrobromic Acid

Discussion: For this experiment our primary goal was to observe and note the reaction of butanols with hydrobromic acid. Before the lab began we discussed and proposed mechanisms. (see “Mechanisms”) To begin this experiment we calculated how much of each material we were going to be using, and the numbers we chose to use differed from our reference text slightly. We used 6.5 mL of our assigned butanol and only 4 mL of sulfuric acid. Going back to our reaction mechanisms, we were looking at SN1 and SN2 reactions, so we of course used the hydrobromic acid as our acid catalyst which would be protonating the hydroxyl group of our butanol, to make a better leaving group, so that the bromine radical would be able to attack the leftover carbocation. Our group used 2-bromobutanol and we expected, from our mechanism, to achieve 2-bromobutane and when we compared our GC results to the prepared sample, our mechanism proved to be true. We did have some small hiccups in our experiment, but less than most of the class, for example, after distillation, when we were drying our organic layer (containing our sample) with anhydrous sodium sulfate, we were unable to achieve to clear color we were told to expect even though our sodium sulfate beads we no longer clumping. We spent extra time trying to gain the ‘clear’ color for our sample to be run through GC, but eventually had to run it ‘as-is’ and it turned out to be relatively free of impurities, like the water we thought was left behind. Also, our lab reference called for us to obtain an IR spectrum, but we ran gas chromatography instead and it, along with our prepared reference of possible products, proved just as successful in identification. We did not measure the melting point of our product