Study Set Content:
Alcohols exhibit a wide range of spontaneous chemical reactions due to the cleavage of the
C-O bond and O-H bond.
presence of an oxidizing agent to produce
aldehydes and ketones
which upon further oxidation give
- carboxylic acids.
upon treatment with protic acids, alcohols undergo dehydration (removal of a molecule of water) to form
alkenes
Strength of an acid in water can be expressed by an acidity constant
Ka
Smaller Ka and larger pKa,
less acidic
Larger Ka and smaller pKa,
more acidic
- Effect of alkyl substitution on alcohol acidity is primarily due to solvation of alkoxide ion formed on acid dissociation
- Effect of alkyl substitution on alcohol acidity is primarily due to solvation of alkoxide ion formed on acid dissociation
are more acidic than alcohols due to resonance stabilization of the phenoxide ion
Phenols
more acidic phenol
Phenols with an electron-withdrawing substituent
less acidic phenol
phenols with an electron-donating substituent
The alcohol hydroxyl can be converted to many other
Functional groups
- In hydroboration of alkenes, indirect methods used are:
- Hydroboration-oxidation, yielding the syn, non-Markovnikov hydration product
- Oxymercuration-demercuration yielding Markovnikov hydration product
Reduction of a carbonyl compound gives an
alcohol
Alcohols from Carbonyl Compounds: Reduction
- Reduction of a carbonyl compound gives an alcohol
- Addition of H to a C=O bond
Reduction of aldehydes gives
primary alcohols
Reduction of ketones gives
secondary alochol
Reduction Reagent:
Sodium Borohydride (NaBH4)
is not sensitive to moisture and can be used with either water or alcohol
NaBH4
Mechanism of Reduction
- Addition of a nucleophilic hydride ion to the positively polarized, electrophilic carbon atom of the carbonyl group
- Alkoxide ion is protonated to yield the alcohol product
