Alcohols and Phenols
and how to identify them
Classification
•
Primary: carbon with –OH is bonded to one other carbon
•
Secondary: carbon with –OH is bonded to two other carbons
•
Tertiary: carbon with –OH is bonded to three other carbons
•
Aromatic (phenol): -OH is bonded to a benzene ring
2
Classify these:
CH3
CH3
CH3
CH CH2OH
CH3
C OH
CH3
OH
OH
CH3
CH CH2CH3
3
IUPAC Nomenclature
•
Find the longest carbon chain containing the carbon with the -OH group
•
Drop the -e from the alkane name, add –ol
•
Number the chain, starting from the end closest to the -OH group
•
Number and name all substituents. =>
4
Name these:
CH3
CH3
CH CH2OH
2-methyl-1-propanol
OH
CH3
CH CH2CH3
2-butanol
CH3
CH3
OH
C OH
CH3
2-methyl-2-propanol
Br
CH3
3-bromo-3-methylcyclohexanol
=>
Chapter 10
5
Naming Phenols
•
-OH group is assumed to be on carbon 1
•
For common names of disubstituted phenols, use ortho- for 1,2; meta- for
1,3; and para- for 1,4
•
Methyl phenols are cresols.
OH
Cl
3-chlorophenol
meta-chlorophenol
OH
H3C
4-methylphenol
para-cresol
6
Physical Properties
•
Unusually high boiling points due to
hydrogen bonding between molecules
•
Small alcohols are miscible in water, but
solubility decreases as the size of the alkyl
group increases.
7
Acidity of Phenol
• In water, phenol acts as a weak acid
phenol
phenoxide ion
Oxidation of Alcohols:
Do I have a tertiary alcohol?
•
•
•
For Primary alcohols that dehydrogenate from the aldehyde to the carboxylic
acid
tertiary alcohols do not dehydrogenate (oxidize)
Secondary alcohols only oxidize to the ketone
+ Cr3+
+ Cr3+
If chromic acid is used for H2CrO4=[O] then the product includes Cr3+ which is
green
9
Oxidation with Chromate
Negative test
tertiary alcohol
Positive test
primary or
secondary
alcohol
Test of a Phenol: FeCl3 test
• You can test for a phenol with ferric chloride
(FeCl3)
Phenol + Fe3+  [Fe3+.phenol complex]
colorless yellow
purple
Experiment
You will test the following
• ethanol
• 2-propanol
• 2-methyl-2-propanol
• Cyclohexanol
• Phenol
• Unknown
Experiment
•
•
•
•
•
•
Odor
Solubility in water
Acidity
Reaction with Chromic Acid
Ferric Chloride Test
Use test results to identify your unknown