Part a: Dehydration of 1-Butanol & 2-Butanol/Part B: Dehydrobromination of 1-Bromobutane & 2-Bromobutane
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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… That the more stable alkene trans-2-butene, is the major product at approximately 82%. While, the two minor products would be 1-butene at 14%, and cis-2-butene at only approximately 4%.
Although, dehydration was not performed on 2-butanol, it would also produce the 3 isomeric alkenes like 1-butanol via an E2 mechanism. The percentages would probably be very similar as well. With trans-2-butene, being the major product, and cis-2-butene and 1-butene being minor products as well. The GC results would appear again very similar to 1-butanol with 3 peaks representing the 3 alkenes produced, however, 2-butanol has a lower BP, so it takes longer to react and produce gaseous mixture because it is a secondary alcohol.
Part B: Dehydrobromination of 1-bromobutane & 2-bromobutane Compound | Temperature (⁰C) | Products | Peak Area(mm2) | % Composition | 1-bromobutane | 90 | Trans-2-butene | ----- | ---- | | | Cis-2-butene | ----- | ---- | | | 1-butene | 17500 | 100 | 2-bromobutane | 80 | Trans-2-butene | 2469 | 49.95 | | | Cis-2-butene | 3336 | 13.09 | | | 1-butene | 8741 | 36.97 |
-(GC) Calculations for relative amount of products:
Total peak area=17500 mm2
17500 mm2/17500 mm2x100%=100%, 1-butene
Total peak area=6679mm2
2469 mm2/6679 mm2x100%=36.97%, 1-butene
3336 mm2/6679 mm2x100%-=49.95% trans-2-butene
8741 mm2/6679 mm2x100%=13.09% cis-2-butene
1-bromobutane with a strong base reacts