Identify an Unknown
Type of compound:
Aldehyde
Alcohol
Amine
Ketone
Procedure
1. Physical Properties
Melting point or boiling point
2. Functional Group
Infrared spectrum
NMR Spectrum
Solubility
Classification Tests
3. Solid Derivative
Measure boiling point of liquids
Distill your unknown and note the boiling point
If can’t distill or not enough
sample use this technique.
Functional Group
Carbonyl Group (1650 - 1725 cm-1)?
No
Yes
Alcohol
Amine
Aldehyde
Ketone
Broad
OH in IR
NMR
+
-
Aldehyde Ketone
Yes
Alcohol
No
Amine
(Basic?)
3700 - 4000 cm-1
Yes
Primary or Secondary
No
Tertiary
2,4-dinitrophenylhydrazine test
NH2NH
NO2
NO2
Aldehyde or ketone
2,4-dinitrophenylhydrazone
O
+
R-C-R
NH2NH
NO2
NO2
R
C
R
NO2
NNH
NO2
DNP Mechanism
OH
O
C
NH2R
C
C
NR
NHR
Iodoform Test
Reagent: NaOH and I2 (NaOI)
O
RCCH3
I2, NaOH
RCOOH + CHI 3
Yellow
Iodoform Test
O
RCCH3
I2, NaOH
RCOOH + CHI 3
Yellow
OH
RCHCH3
I2, NaOH
RCOOH + CHI 3
Yellow
Iodoform Test
Ceric Nitrate Test for Alcohols
(NH4)2Ce(NO3)6 + ROH
(NH4)2Ce(NO3)5OR
+ HNO3
Amines
1. Odor
2. If not soluble in water they may
dissolve in dilute aqueous acid (HCl).
3. Water solutions of amines are
basic to litmus.
Hinsberg Test for Amines
SO2Cl
Benzenesulfonyl Chloride
Hinsberg Test for Amines
Primary: Soluble. PPT if add HCl
Secondary: Insoluble
Tertiary: Tends not to react
Derivatives
Aldehydes and Ketones
1. 2,4-dinitrophenylhydrazone
2. Semicarbazone
O
O
O
NH2NHCNH2 +
RC R
semicarbazide
R
C
NNHCNH2
R
semicarbazone
Alcohol Derivative
O2N
O2N
O
O
ROH
C Cl
O2N
3,5-dinitrobenzoyl
chloride
C OR
O2N
3,5-dinitrobenzoate
Amine Derivatives
Primary and Secondary Amines
O
O
C Cl + RNH 2
C NHR
Benzoyl Chloride
SO2Cl + RNH 2
Benzenesulfonyl Chloride
Benzamide
SO2NHR
Benzenesulfamide
Sample
Unknown
B.p. =198-200o
DNP = 231-235o
Table
Structure of Unknown
O
C
acetophenone
CH3
Sample Unknown
B.p. = 80 - 85o
3,5-dinitrobenzoate
= 119 - 121o
OH
CH3
C
CH3
H
isopropyl alcohol
B.p = 106o
3,5-dinitrobenzoate
85o
CH3
CH
CH2OH
CH3
isobutyl alcohol
B.p. = 160o
3,5-dinitrobenzoate:
108-110o
H
OH
cyclohexanol
B.p. = 155-157o
2,4-DNP = 158 160o
O
cyclohexanone
B.p. = 180 -183o
Benzenesulfonamide
110 - 112o
Benzamide 160 - 163o
NH2
aniline