Download L3 - Alcohol and Phenol Reactions

Reactions Involving Alcohols
Review:
dehydration
dehydration (elimination) The
removal of water from an alcohol to
produce an alkene.
For reaction that yield multiple possible
products, the major product is predicted
using Saytzeff’s Rule
A simplified mechanism for dehydration follows:
1. Protonation of alcohol
3. The Resulting carbocation loses a hydrogen to
the catalyst ion from an adjacent carbon to form
an alkene while the catalyst is regenerated.
2. Loss of water resulting in carbocation formation
You are not responsible for this mechanism
Alcohol Reactions
Dehydration
Dehydration Synthesis
(elimination) Under slightly different
conditions, a dehydration reaction can
occur between two alcohol molecules to
produce an ether.
dehydration synthesis occurs at lower
temperatures than normal dehydration
and results in the formation of a new
functional group.
Alcohol Reactions, cont.
Oxidation – Oxidation reactions occur when a
molecule gains an oxygen, loses a hydrogen or
loses electrons.
Under the right conditions, alcohols can by
oxidized by removing two hydrogen atoms from
the same molecule, one from a hydroxyl group
and the second from the carbon of the hydroxyl
group, resulting in the formation of a double
bond between the carbon and remaining oxygen
atoms.
Alcohol oxidations will occur in the presence of
an oxidizing (O) agent:
•K2Cr2O7 and KMnO4 are common oxidizing agents
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Alcohol Reactions, cont.
Primary
Primary alcohol oxidation
•A primary alcohol can undergo a two
step reaction:
–In the first reaction, the alcohol loses two
hydrogen atoms to form a carbonyl group
on a terminal carbon by an oxidizing
agent (O), creating an aldehyde.
–In the second reaction, the newly formed
aldehyde can undergo further oxidation
when the remaining hydrogen one the
carbonyl carbon is substituted with a
hydroxyl forming a carboxyl group,
creating a carboxylic acid.
Alcohol Reactions, cont.
Secondary
Secondary alcohol oxidation
•A secondary alcohol can only undergo
one oxidation
–the alcohol loses two hydrogen atoms to
form a carbonyl group on an intermediate
carbon, creating a ketone.
– What about a tertiary alcohol?
Reactions with Phenols
Phenol behaves as a weak acid in water
And can react with bases to form salt.
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