Qualitative Identification of
Functional Groups
Organic Functional Groups
• Functional group is the site in an organic
molecule where a reaction may take place.
• There 10 organic functional groups.
• Today’s lab will focus on the qualitative
identification of alcohols, phenols, aldehydes,
ketones, and alkenes.
Alkenes - unsaturated
Alcohols – primary, secondary and
tertiary
Phenols
Aldehydes and Ketones
Tests for alcohols
• Ceric Ammonium Nitrate
– Primary, secondary and tertiary alcohols of up to
10 carbons
• Chromic Acid
– Primary and secondary alcohols, (not tertiary!)
• Zinc Chloride in HCl (Lucas Test)
– Water soluble secondary and tertiary alcohols,
(not primary!)
Tests for phenols
• Bromination
• Ferric Chloride
Test for ketones
• 2,4-Dinitrophenylhydrazine Test
Tests for aldehydes
• Chromic oxide
– Aldehydes react in 5 – 15 seconds
• Tollen’s Test
• 2,4-Dinitrophenylhydrazine test
Test for alkenes
• Bromination
Ceric ammonium nitrate test –
Alcohols of up to 10 carbons
Chromic Oxide and Sulfuric Acid
Primary and Secondary Alcohols
Zinc Chloride in HCl (a.k.a Lucas Test)
• Tests for the presence of secondary and tertiary alcohols only.
• Low molecular mass alcohols are polar and water soluble. In this reaction
they are changed to alkyl halides which are insoluble in water. A positive
test will be the presence of an insoluble second layer.
• Secondary alcohol - solution turns cloudy in 3-5 minutes:
• Tertiary alcohol - solution turns cloudy immediately, and/or phases separate
Tollen’s Test
• Test for aldehydes
• Positive test is the appearance of a mirror-like
deposit on the test tube.
• Aldehydes are oxidized to a salt of a carboxylic acid.
• Plus Ag(s)
2,4-Dinitrophenylhydrazine test
• This is a test for aldehydes and ketones
• A positive test is the formation of a canary
yellow to scarlet precipitate.
2,4-Dinitrophenylhydrazine test
(for aldehydes)
2,4-Dinitrophenylhydrazine test
(for ketones)
Bromination Test
• Tests for the presence of a pi bonds.
• In alkenes and alkynes, no HBr is produced and it is
an addition reaction. In the presence of phenol HBr
is produced and it is a substitution reaction.
Ferric Chloride
• Test for the presence of a phenol.
• Positive test is a color change from an orangeyellow to a burgundy color.
+ 3 HCl