1) The document provides guidance for an experiment to identify an unknown organic compound through a series of chemical tests and analysis of spectroscopic data. 2) It outlines a 4 step general process: characterization of functional groups, listing possible structures and obtaining derivatives, determining the unknown structure, and proposing the structure. 3) Key advice includes maintaining good documentation, being aware of false positives/negatives, and making logical decisions when results are contradictory.

1. General Notes
1) Lab Report Due for Experiment #8 (Grignard) Nov. 29/30
- Note: i) the 1H NMR spectrum of the final product is provided on the
website for comparison (only NMR provided and will need to
be interpreted – along with your experimentally determined
NMR spectrum)
ii) NMR solvent is DMSO (peak at 2.49 ppm)
2) Lab Report Due for Experiment #9 (Unknown): Dec. 6/7
3) No lecture next week (Friday, November 19), Extra Office Hour
4) Review Session: Friday, December 3 in W 151 PBB
5) Exam 2, Friday December 10, will be held in W 151 PBB
6) Regrades of Exam 1 available in Chemistry Center and regrades
of labs will be handed back by your TA
Experiment #9:
Identification of Unknown Sample
- purpose of the experiment is to determine the structure of an unknown
compound using chemical tests and spectroscopic data normally
available in an organic laboratory
Advice
- it is crucial to maintain a good written account of each step
- beware of false positives and false negatives
- be ready to make decisions between contrary information
Functional Groups
R OH
OH
O
R H
O
R R
O
R OH
O
R OR
R
N
H H
alcohol
phenol
aldehyde
ketone
carboxylic acid
ester
amine

2. Four General Steps
1) Characterize/Functional Group Tests
2) List Possible Structures/Obtain Derivatives
submit list to TA
3) Unknown Structure?
receive list back?
receive NMR?
4) Propose Structure for Unknown
Characterize/Functional Group Tests
1) Obtain unknown from TA
2) Note appearance (solid, liquid, color, crystalline, etc.)
3) Determine solubility (organic, aqueous, aq. NaHCO3, aq. NaOH, aq. HCl)*
4) Prepare unknown sample for NMR analysis
5) Obtain melting point or boiling point (repeat for accuracy)
6) Burn small amount of sample (aromatic flame test)
7) Obtain IR [liq.(neat), solid (nujol, CCl4, CHCl3)]
8) Conduct at least three functional group tests (should run positive controls)*
Step 1 - Solubility Test
insoluble
insoluble
insoluble
aliphatic amines
1° aromatic amines
soluble
soluble
soluble
insoluble
soluble
p H t e s t
HCl (aq)
oxygen containing compounds
alkenes, alkynes,
activated aromatics
alkanes, haloalkanes,
unactivated aromatics
carboxylic acids, some
highly acidic phenols
phenols
1,3-diketones
low MW ( < 5 C's) with
hydrophilic groups
insoluble
soluble
unknown
water
NaHCO3 (aq)
NaOH (aq)
H2SO4 (con)

3. Functional Group Tests
Alkenes (Bromination)
Aromatics (Flame Test)
H3C
Alkyl Halides (Beilstein Test, Silver Nitrate Test)
CH3
Br
H3C
Br
CH3
+ Br2 + CCl4
+ O2 C (soot) + CO2 + H2O
RCH2Cl
Δ
green flash
Cu
RCH2Cl
AgNO3 precipitate? (false positive with carboxylic acid)
Alcohols (Lucas Test, Chromic Acid Test)
RR’(H)COH + ZnCl2 RR’(H)CCl (ppt) (3o immed. ppt.)
O
RC(H)COH + HCrO3 + RC(H)CO2H (1o & 2o blue-green)
Phenols (Ferric Chloride Test, Bromine Test)
OH
OH
+ FeCl3 red, blue, purple metal-complex
+ EtOH + Br2 (yellow)
OH
Br
+ HBr
(litmus paper)
Aldehydes & Ketones (Dinitrophenylhydrazine, Tollens, Iodoform)
O
R R'(H)
O
R H
O
+
NO2
O2N
NNH
R
(H)'R
(ppt.)
+ NH3·Ag+ + Ag0 (silver mirror/black ppt.)
+ NaOH + I2 (brown)
R CH3
NO2
O2N
H2NNH
O
R OH
Carboxylic Acids (Acidity, Bicarbonate)
O
R OH
+ H2O
+ NaHCO3(aq)
CHI3 + NaI + H2O
RCO2
(pale yellow)
- + H3O+ (reduced pH)
RCO2
- + Na+ (aq. solubility) + CO2

4. Amines (Basicity, Hinsberg Test)
RNH2 + H2O RNH3
+ + -OH (increased pH)
SO2Cl
CH3
RNH2 +
R2NH
R3N
(solubility test: NaOH, H2O)
Esters (Hydroxyl Amine/Ferric Chloride)
SO2N(H)R
CH3
SO2
-+NR3
CH3
or
O
R O
R' + HONH3
+Cl- + EtOH/KOH
O
R N
H
OH
FeCl3 (purple)
Nitro Compounds (Iron(II) Hydroxide Test)
RNO2 + (FeNH4)2(SO4)3 + H2SO4 + KOH/EtOH (blue ppt. turns
brown)
List Possible Structures/Obtain Derivatives
1) Develop a list of possibilities from the chart in the lab (and on web)
2) Propose 3-5 structures based on properties and derivatives
3) Submit your list of possible structures to TA (use datasheet)
a) give chemical names
b) give chemical structures
c) give known mp range of derivatives
4) Synthesize appropriate derivative and obtain melting point (sharp)
Derivatives
Alcohols
Phenols
N C O NH
O
O
R
O2N
O2N
O
Cl
O2N
O2N
O
OR
OH
OH
OH
O2N
O2N
O
Cl
Br OH
O2N
O2N
O
OPh
NH
O
O
Ph
N C O
ROH +
ROH + + pyridine
+
+ + pyridine pyridine·HCl +
+ Br2/H2O
pyridine·HCl +

5. Aldehydes and Ketones
O
R R'(H) NO2
+ + NaOAc
Carboxylic Acids
O2N
H2NNH
+
O
R R'(H)
O
H2NN NH2
·HCl
O
R OH
O
R Cl
+ SOCl2
H3C NH2
O
R Cl
+
R
R
+ HCl + SO2
+ HCl
1)
2)
NH
O
H3C R
O
NNH NH2
(H)R'
NO2
O2N
NNH
(H)'R
Esters
O
R O
R' + NaOH/HOCH2CH2OH
Primary and Secondary Amines
O
R O-Na+
O
R OH
H+/H2O
O
O
O
O
Cl
RR’NH + NaOAc +
+
Tertiary Amines
RR’R’’N: + CH3I RR’R’’NCH3
(then carboxylic
acid derivative)
O
RR'N
RR'N
O
+I- (conduct reaction in hood)
Unknown Structure?
1) If you receive list back – more experimental work is needed
- three total attempts (attempts #2 and #3 result in a 5 pt. deduction each)
2) If you receive spectrum – interpret, synthesize derivative, and define unknown
Propose Structure of Unknown
1) Propose a single structure for unknown
2) Prepare unknown report

6. Procedures and Precautions
1) beware of false positives and false negatives (outlined in course pack)
- example: FeCl3 test does not work with all phenols (e.g. steric effects)
2) use fresh sample for each solubility test
3) use ‘clean’ glassware
- Note: acetone is a ketone (e.g. participates in iodoform test)
4) have material ready for NMR analysis on Day 1
5) crucial to maintain a good written account of each step
6) provide logical account of decision making in lab report
7) do not overuse all of your sample (5 pt. deduction)