Lab 7: OCHEM 1 | Questions and Answers| Well
reviewed
The dehydration of alcohol produces **** an alkene by functional group transformation
Cyclohexanol is converted into an alkene by elimination of... **** water
Dehydration Mechanisms: **** 1. Protonation of the Alcohol (acid-base reaction
involving electron pairs on the oxygen atom of the alcohol)
2. Loss of water to give a carbocation
3. Deprotonation and double bond formation.
In the overall mechanism there is no consumption of.. **** acid; we just use it to
facilitate the protonation.
The acid acts as a catalyst by... **** catalyzing the dehydration by lowering the energy
required to cleave the carbon-oxygen bond.
Is the reaction reversible? **** Yes
The boiling point of the alkene is lower than the **** alcohol
The acid catalyst is **** phosphoric acid, which has a higher boiling point and remains
behind in the reaction vessel.
Thus, the distillate contains no... **** acid which might catalyze the reverse reaction.
Why did we choose phosphoric acid? **** The phosphate counter ion is non-
nucleophilic which minimizes substitution pathways.
We are using fractional distillation to isolate the alkene, why is it important that there is
not a gap between the bent adapter and the graduated cylinder? **** Cyclohexene has
quite a low boiling point, and if there is a gap, there will be product loss by evaporation.
Why do we add water to the reaction? **** It helps drive the equilibrium reaction
towards the alkene, we're adding it so it can be eliminated. Thus, it prevents the reverse
reaction from occuring.
The Bromine and The Baeyer test for.. **** the presence of alkenes or alkyne
Bromine Test Procedure **** A positive test for an alkene or alkyne is the continued
rapid disappearance of the red color with no significant evolution of HBr
reviewed
The dehydration of alcohol produces **** an alkene by functional group transformation
Cyclohexanol is converted into an alkene by elimination of... **** water
Dehydration Mechanisms: **** 1. Protonation of the Alcohol (acid-base reaction
involving electron pairs on the oxygen atom of the alcohol)
2. Loss of water to give a carbocation
3. Deprotonation and double bond formation.
In the overall mechanism there is no consumption of.. **** acid; we just use it to
facilitate the protonation.
The acid acts as a catalyst by... **** catalyzing the dehydration by lowering the energy
required to cleave the carbon-oxygen bond.
Is the reaction reversible? **** Yes
The boiling point of the alkene is lower than the **** alcohol
The acid catalyst is **** phosphoric acid, which has a higher boiling point and remains
behind in the reaction vessel.
Thus, the distillate contains no... **** acid which might catalyze the reverse reaction.
Why did we choose phosphoric acid? **** The phosphate counter ion is non-
nucleophilic which minimizes substitution pathways.
We are using fractional distillation to isolate the alkene, why is it important that there is
not a gap between the bent adapter and the graduated cylinder? **** Cyclohexene has
quite a low boiling point, and if there is a gap, there will be product loss by evaporation.
Why do we add water to the reaction? **** It helps drive the equilibrium reaction
towards the alkene, we're adding it so it can be eliminated. Thus, it prevents the reverse
reaction from occuring.
The Bromine and The Baeyer test for.. **** the presence of alkenes or alkyne
Bromine Test Procedure **** A positive test for an alkene or alkyne is the continued
rapid disappearance of the red color with no significant evolution of HBr
