CHM 235LL-Monday, 3/19/2012 & 3/26/2012
Part A: Dehydration of 1-butanol & 2-Butanol/Part B: Dehydrobromination of 1-Bromobutane & 2-Bromobutane
The objective of this experiment is to successfully perform a dehydration of 1-butanol and 2-butanol, also dehydrobromination of 1-bromobutane and 2-bromobutane to form the alkene products 1-butene, trans-2-butene, and cis-2-butene. The dehydration reactions react under and acid-catalysis which follows an E1 mechanism. It was found that dehydration of 1-butanol yielded 3.84% cis-2-butene, 81.83% trans-2-butene, and 14.33% 1-butene, while 2-butanol is unknown due to mechanical issues with the GC machine. For the dehydrobromination, with the addition of a …show more content…
Therefore, there is only one major product.
As well 2-bromobutane reacts via E2 mechanism, but a secondary alkyl halide like 2-bromobutane, on the other hand, have five β-hydrogens that can be removed. Removing a proton (a β-hydrogen) from the primary carbon produces 1-butene. However, removing a proton (a β-hydrogen) from the secondary carbon produces 2-butene, with two possible stereoisomers, either cis-, or trans-. Trans, being the major product because it is the most stable.
Areas for improvement would be to make sure the equipment is properly clean and dry to avoid potential contaminants which could potentially affect rate of reaction and show up in GC. Also, to maintain the appropriate temperature range so that the reactant does not heat too quickly. Lastly, taking care that the o-ring is tightly secure to keep gas in the column so that it can collect in the tube with septum.
Overall, the dehydration of 1-butanol, and the dehydrobromination of 1-bromobutane, and 2-bromobutane was successful, in producing consistent and accurate GC results following E1 (1st order) and E2 (2nd order) reaction mechanisms. All but one compound produced three isomeric alkenes, which are based on the mechanism of the reactions, as well as the similarities of the compositions. The compositions were similar in their ability to produce the alkenes, however varied