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The Effect Of Dehydration Of Cyclohexene

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In this experiment, dehydration is carried out using cyclohexanol to obtain cyclohexene. This acid-catalysed reaction involves E1 elimination mechanism. The dehydration of alcohol will remove OH- from cyclohexanol to form cyclohexene. Cyclohexene contains a single double bond in the molecule. It is a six carbon aromatic hydrocarbon. Phosphoric acid is mixed with cyclohexanol in the round-bottomed flask and is heated. The phosphoric acid act as a catalyst that increases the rate of reaction but it does not change the overall stoichiometry. The acid catalyst will convert the hydroxyl group into a good leaving group. It is an equilibrium reaction in which the equilibrium is forced to the right (alkene). (Department of Chemistry 2014) Boling chips are added to the distillating flask. If not, the liquid may over boil and shoot out of the …show more content…

E1 reaction is a two-step mechanism which includes the protonation of hydroxyl group and the formation of carbocation intermediate (rate-determining step).

Questions:
1. Dehydration of cyclohexanol gives cyclohexene. Draw mechanism for the reaction.

2. What alkene(s) will be produced when each of the following alcohols is dehydrated?
a) t-butyl alcohol CH3 CH3 CH3 C OH CH3 C = CH2 + H2O CH3 Ans: 2-methyl-1-propene
b) 3-methylcyclohexanol
Ans: 1-methylcyclohexene, 3-methylcyclohexene and 4-methylcyclohexene.
3. The dehydration of 3,3-dimethyl-2-butanol yields three different products. Write equations to show how carbocation rearrangements explain two of the products.
Ans: A secondary carbocation is formed initially, it then rearranges to a tertiary carbocation when a neighbouring methyl group with its bonding electron pair migrates to the positive carbon. The charge is transferred to the tertiary

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