Part a: Dehydration of 1-Butanol & 2-Butanol/Part B: Dehydrobromination of 1-Bromobutane & 2-Bromobutane
Ashley Droddy
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
Abstract
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 strong base that can abstract a proton, which then pushes off the leaving group and a new sigma bond makes a new π-bond all at one time, this is follows E2 mechanism. It was found that the dehydrobromination of 1-bromobutane yielded 100% 1-butene, while 2-bromobutane yielded 13.09% cis-2-butene, 49.95% trans-2-butene, and 36.97% 1-butene.
Introduction
For E1 (1st order) reaction mechanisms, under acid-catalysis an alcohol may be dehydrated to form an alkene. The most common acids employed for the reaction are sulfuric or phosphoric acids. The reaction proceeds via initial protonation of the hydroxyl group (a typical acid-base reaction). This converts the hydroxyl unit from a poor leaving group (-OH) into a much better one (H2O). Loss of water generates a carbocation, which can stabilize itself by elimination of a proton from an adjacent carbon to produce the alkene. The elimination of the proton will predominately occur in the direction that results in the production of the more highly substituted carbon-carbon double bond.
The carbocation has other fates depending upon substrate, reaction conditions, and acid employed. The carbocation can undergo rearrangement to a more stable species for example, 1°to a 2°, or 3°, via a
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
Abstract
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 strong base that can abstract a proton, which then pushes off the leaving group and a new sigma bond makes a new π-bond all at one time, this is follows E2 mechanism. It was found that the dehydrobromination of 1-bromobutane yielded 100% 1-butene, while 2-bromobutane yielded 13.09% cis-2-butene, 49.95% trans-2-butene, and 36.97% 1-butene.
Introduction
For E1 (1st order) reaction mechanisms, under acid-catalysis an alcohol may be dehydrated to form an alkene. The most common acids employed for the reaction are sulfuric or phosphoric acids. The reaction proceeds via initial protonation of the hydroxyl group (a typical acid-base reaction). This converts the hydroxyl unit from a poor leaving group (-OH) into a much better one (H2O). Loss of water generates a carbocation, which can stabilize itself by elimination of a proton from an adjacent carbon to produce the alkene. The elimination of the proton will predominately occur in the direction that results in the production of the more highly substituted carbon-carbon double bond.
The carbocation has other fates depending upon substrate, reaction conditions, and acid employed. The carbocation can undergo rearrangement to a more stable species for example, 1°to a 2°, or 3°, via a