Organic Qualitative Analysis
Physical Properties, Chemical tests and Infrared
Spectroscopy to Identify:
Unknown Halide
(primary, secondary, tertiary)
Hydrocarbon
(alkane, alkene, aromatic)
Alcohol
(primary, secondary, tertiary)
References:
Slayden, S., Stalick, W.; 2010, Catalyst - Organic
Chemistry Laboratory Manual, GMU Print Services
Pavia, D., Lampman, G., Kriz, G, Engel, R, 2010, A Small
Scale Approach to Organic Laboratory Techniques, 3nd
ed, Cengage Learning
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1
Organic Qualitative Analysis

Purpose: Become familiar with a combination of physical
and chemical tests for characterizing classes of organic
compounds. To use these tests plus Refractive Index and
IR to identify an unknown.

Classes: Compounds without a Carbonyl group or
Nitrogen group

Alkanes
C-C

Alkenes
C=C

Alkynes
C≡C

Aromatics
C=C

Alkyl (1o, 2o, 3o) & Aryl Halides
R-X

Alcohols (1o, 2o, 3o)
R-OH
Note: Tests for carbonyl based compounds (Aldehydes &
Ketones) will be presented next semester
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2
Organic Qualitative Analysis

The Tests – Compound Classes
Test











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Solubility Relative to H2O & H2SO4
Density Relative to H2O
Beilstein (Flame)
Silver Nitrate/Ethanol
Sodium Iodide/Acetone
Bromine/Methylene Chloride
KMnO4 (Baeyer Test)
Ignition
Acetyl Chloride
Lucas Test
Chromic Acid
Compound Class
All
All
Halides
Alkyl & Aryl Halides
Alkyl & Aryl Halides
Unsaturated C=C CC
Unsaturated C=C CC
Aromaticity C=C
Alcohols
Alcohols
Alcohols
3
Organic Qualitative Analysis

The Tests – Test References
(Pavia (3rd ed) – GMU Version or Pavia Main text as
indicated)











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Test
Solubility Relative to H2O & H2SO4
Density Relative H2O
Beilstein (Flame)
Silver Nitrate/Ethanol
Sodium Iodide/Acetone
Bromine/Methylene Chloride
KMnO4 (Baeyer Test)
Ignition
Acetyl Chloride
Lucas Test
Chromic Acid
Page No.
p. 453-458
p. 717-719
p. 459-460
P. 460-461
p. 158 Pavia Main Text
p. 464-466
p. 466-467
p. 467-468
p. 585
p. 585
p. 586-487
4
Organic Qualitative Analysis

Elements of the Experiment

Two week experiment

Pre-lab must cover both weeks

Week I
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
Purification & Boiling Point via Simple Distillation

Physical Characteristics of the purified sample

Solubility in Water (H2O) & Conc Sulfuric Acid (H2SO4)

Density relative to Water

Refractive Index

Beilstein Test for Halides

Ignition Test for Aromaticity

IR Spectrum
5
Organic Qualitative Analysis

Elements of the Experiment (Con’t)

Week I (Con’t)

Chemical Tests for known compounds

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Tests

Bromine in Methylene Chloride (Unsaturation)

Baeyer (KMnO4) Test (Unsaturation)

Acetyl Chloride (Alcohols)

Lucas Test (Primary, Secondary, Tertiary, Benzylic
Alcohols)

Chromic Acid Test (Primary, Secondary, Tertiary
Alcohols)
6
Organic Qualitative Analysis

Known Compounds
 Halides
 1-Chlorobutane
 2-Chlorobutane
 T-Butyl Chloride (2-Chloro-2-Methyl Propane)
 Chlorobenzene
 Hydrocarbons
 Cyclohexane
 Toluene
 Cyclohexene
 Alcohols
 1-Butanol
 2-Propanol
 T-Amyl Alcohol (2-Methyl-Butanol)
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7
Organic Qualitative Analysis

Elements of the Experiment (Con’t)
 Week I (Con’t)
 Chemical Tests for known compounds (Con’t)

Approach
 Each “known” compound is to be run against
just those tests for which it is applicable
 Ex.
2-Chlorobutane is to be run against AgNO3
in Ethanol and NaI in Acetone (week 2)
Cylcohexene is to be run just against
Bromine in Methylene Chloride & KMnO4
Toluene is to be run just against Bromine in
Methylene Chloride & KMnO4
2-Propanol is to be run just against Acetyl
Chloride, Lucas Reagent and Chromic Acid
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8
Organic Qualitative Analysis

Elements of the Experiment (Con’t)

Week II

Continuation of known compounds
 Tests
 Silver
Nitrate/Ethanol
 Sodium

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Iodide/Acetone
Alkyl & Aryl Halides
Alkyl & Aryl Halides
Unknown Compound
 Based on the results of the refractive index,
Beilstein test, Ignition Test and IR Spectroscopy,
the student will select the test(s) for which
his/her unknown is applicable.
Ex:
If IR indicates alcohol, unknown will be run
against Acetyl Chloride, Lucas Reagent &
Chromic Acid.
9
Organic Qualitative Analysis

General Notes

Dangerous Chemicals – Acetyl Chloride, Conc H2SO4
Use Gloves, Goggles, and Lab Coat (Buttoned)

Use a test tube rack from cabinet

Use medicine droppers from equipment set
Pasteur pipettes are not available

Make sure to wash and dry the medicine dropper and
test tubes for each test

Set up water baths (50oC & 100oC) using 250 mL
beakers on each bench for the Halide tests (Silver
Nitrate & Sodium Iodide)
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10
Organic Qualitative Analysis
General Notes

The Beilstein (flame) Test for Halides and the Ignition
test for Aromaticity with be done in the hood with the
assistance of the instructor

Record the results of the chemical tests in a 5-column
table created in the pre-lab template (see slide 15)

Use simple, direct language to describe your test; it is
very important to describe an observation completely
Ex. The Unknown was soluble in water

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Be sure to obtain a good positive result for each test;
repeat the test until a good positive result is obtained
11
Organic Qualitative Analysis

Testing Sequence for Knowns & Unknown
 The
Boiling Point, Solubility, Refractive Index, Flame
tests, and IR should indicate the general class of the
unknown compound – Halogen, Hydrocarbon, Alcohol
 Test
your unknown and all the known compounds
against only those tests for which the compounds are
applicable, e.g., Sodium Iodide & Silver Nitrate for
Halides; KMnO4 & Bromine in Methylene Chloride for
Hydrocarbons, Acetyl Chloride & Chromic Acid for
alcohols
Note: See table on page 69 of Slayden Lab Manual
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12
Organic Qualitative Analysis
 For
each test, set up a sufficient number of test tubes
to accommodate the unknown and the applicable
number of knowns for that test
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
Add test reagent

Add compound to be tested; shake mixture

Heat reaction mixture if specified in test directions
13
Organic Qualitative Analysis

The Report
 Each “Test” is a Procedure and must be set up with:
 A Title
 Materials & Equipment, including reagents, known
and unknown compounds, test tubes
 Procedure Description in bullet format
 Test Results – include a 5-column table (see next
slide) containing the name of the compound, your
observations, and an indication of whether a result
for a givent compound was positive or negative
relative to the compound tested and the test applied
 Summary – All results summarized in a paragraph
 Analysis & Conclusions
 Arguments showing how your results support your
identification of the unknown
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14
Organic Qualitative Analysis

Suggested table for recording Qualitative Organic test
results. You can paste this table into your report
 The positive/negative column should be left blank for
the unknown
 Indicate positive or negative for just the known
compounds, since you know the class of the compound
Compound
Unknown
Observation
Observation
Observation
Positive(+) /
(Rm Temp)
50oC
100oC
Negative (-)
Leave Blank
Known #1
Known #2
Known #3
Note: For tests not involving temperature differentials,
leave the 50oC & 100oC blocks blank or just
remove the columns
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15
Organic Qualitative Analysis
Sample Purification / Boiling Point

Organic Lab – Unknowns, Purification, Boiling Point

Several experiments in Chem 315/318 (Org Lab I & II)
involve the identification of an unknown compound

Liquid samples that students receive in Lab may
contain some impurities in addition to the unknown
compound that could produce ambiguous results when
determining the chemical or physical properties of the
compound

Simple Distillation is used to purify the sample by
separating the pure compound that comes over in a
narrow temperature range – corresponding to its
boiling point – from impurities that have boiling points
either lower than or higher than the compound
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16
Organic Qualitative Analysis

Simple Distillation – Background
 Boiling Point
The normal boiling point (also called the atmospheric
boiling point or the atmospheric pressure boiling point)
of a liquid is the temperature at which the vapor
pressure of the liquid is equal to 1 atmosphere (atm), the
atmospheric pressure at sea level
At that temperature, the vapor pressure of the liquid
becomes sufficient to overcome atmospheric pressure
and allow bubbles of vapor to form inside the bulk of the
liquid.
The standard boiling point is now (as of 1982) defined by
IUPAC as the temperature at which boiling occurs under
a pressure of 1 bar
1 bar = 105 Pascals = 0.98692 atmospheres
= 14.5038 psi (pounds per square inch)
= 29.53 in Hg (inches of mercury) = 750.06 mm
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17
Organic Qualitative Analysis

Simple Distillation – Background
Note: The temperature range you obtain for your boiling
point may be inaccurate for three (3) reasons
1. The atmospheric pressure in the lab may not be:
1 bar (0.98692 atm)
2. The thermometers used in the lab may not
reflect the actual temperature
3. The thermal inefficiency of the glassware used for
the boiling point determination may result in a
lower than expected measured value by as much
as 2 – 5oC
You should take this potential temperature differential
into account when you compare your measured results
with the list of possible unknowns in lab manual tables
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18
Organic Qualitative Analysis
Typical Distillation Setup
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19
Organic Qualitative Analysis
Simple Distillation – Procedure

Set up Simple Distillation apparatus (previous slide)

Use 25 mL or 50 mL Distillation flask

Place a Corundum or Teflon boiling chip in the flask

Start gentle water flow through condenser

Put a waste receiving container (small beaker) into an ice
water bath – especially for low boiling liquids.

Begin heating sample
Note: The sample may appear to be boiling, but the
actual boiling point is not reached until the
temperature of the boiling liquid and the vapor
surrounding the thermometer bulb reach equilibrium.
At this point the vapor will start to condense in the
condenser
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20
Organic Qualitative Analysis

Simple Distillation - Procedure
 Note the temperature when the distillate begins to drip into
the waste receiving container
 Continue to collect distillate in the waste container until the
temperature begins to level off
 Remove the waster container and begin collecting the
distillate in a small clean Erlenmeyer flask
 Note the temperature when you start to collect the purified
sample
 Continue to collect the sample until the temperature begins
to rise again (it may not change before the all of the sample
has come over)
 Note the temperature just before the temperature begins to
change
 The first and last temperatures recorded in the narrow
boiling range represent the boiling point range of your
sample
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21
Organic Qualitative Analysis
Solubility Test
(Water (H2O) and Conc Sulfuric Acid (H2SO4)

Only the unknown is to be tested for solubility in
Water and Concentrated Sulfuric Acid

1/17/2015
Water

Compounds with <5 Carbons containing O, N, S are
soluble

Compounds with 5-6 Carbons containing O, N, S are
borderline (slightly soluble)

Branching Alkyl chains result in lower melting/boiling
points and increased solubility

Increase N, O, S to Carbon ratio increases solubility
22
Organic Qualitative Analysis
Solubility Test
(Water (H2O) and Conc Sulfuric Acid (H2SO4)

Conc H2SO4 Solubility
 Compounds containing N, O, S can be protonated in
Conc H2SO4 and thus are considered soluble
 Alkenes (C=C)
 Alkynes (C≡C)
 Ethers
(C-O-C)
 Nitroaromatics (Nitrobenzene)
 Amides
 Alcohols (R-OH)
 Ketones
 Aldehydes
 Esters
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23
Organic Qualitative Analysis
Solubility Test
(Water (H2O) and Conc Sulfuric Acid (H2SO4)

Water & Conc H2SO4 Solubility
 Not soluble
 Alkanes
 Aromatic Hydrocarbons
 Alkyl Halides
 Aromatic Halides
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24
Organic Qualitative Analysis
Relative Solubility & Density

Procedure – Water & H2SO4
Note: Solubility & Density test is performed only
on the Unknown

Place about 2 mL of Distilled Water or Conc H2SO4 in a
test tube

Add 3-5 drops of the compound to be tested

Shake vigorously

Solubility is indicated by a “single” clear liquid, i.e. no
bubble or additional layers

Production of a gas, a change in color, and/or a
change in temperature indicates a chemical reaction;
thus, solubility
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25
Organic Qualitative Analysis
Relative Solubility & Density (Con’t)

Procedure Water & H2SO4 (Con’t)

Density relative to water of an insoluble compound is
indicated by where the insoluble compound settles:
top
(less dense)
suspended (similar density)
bottom

1/17/2015
(more dense)
Solubility of a Hydrocarbon in water indicates 4 or less
carbons
26
Organic Qualitative Analysis

Beilstein Test (General for Halides)
Procedure
 Bend small loop in the end of piece of copper wire.
 Heat loop in Bunsen Burner
 After cooling
 Liquid sample: dip wire in sample
 Solid sample: dip wire in water then sample
 Heat wire
 Compound first burns with yellow flame
 After burning for a few seconds, a green flame is
produced if a halogen is present
 Does not differentiate between Chlorine, Bromine, or
Iodine
 Weak color could indicate present of impurities in a
non-halide sample
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27
Organic Qualitative Analysis


Silver Nitrate in Ethanol Test (Sn1 for Halides)
Sn1 (unimolecular nucleophilic substitution) reactions
depend on:
 Weak electron rich Nucleophile (NO3)
 Polar Solvent (Ethanol)
 Compounds equipped with good leaving groups (H2O,
CL, Br, I)
 The test does not distinguish between Chloride,
Bromine, or Iodine
The Halide (leaving group) is replaced with the Nitrate
nucleophile forming an insoluble white Halide precipitate
 The degree of precipitate formation is dependent on
the relative stability of the compound and the resulting
Carbocation that forms in the reaction
Benzyl  Allyl > Tertiary (3o) > Secondary (2o)
> Primary (1o) > Methyl > Vinyl > Aryl (Aromatic)
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28
Organic Qualitative Analysis
Silver Nitrate in Ethanol Test (Sn1 for Halides)

The Test

Add 1 to 2 drops of liquid sample (or 5 drops of
concentrated Ethanoic solution of a solid sample) to 2
mL of 2% Ethanoic Silver Nitrate

Positive test – cloudy to heavy white precipitate
depending on relative stability of Carbocation
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
Allyl, Benzyl, Tertiary Halides give white precipitate
at room temperature

Primary & Secondary Alkyl Halides test positive
(usually cloudy ppt) when heated (100oC)

Aromatic and many Vinyl Substituted Halides do not
give positive tests
29
Organic Qualitative Analysis
Sodium Iodide in Acetone (Sn2 for Alkyl Halides)
 Sn2 – Bimolecular Nucleophilic Substitution
 Sodium Iodide is soluble in Acetone, but Sodium Chloride
and Sodium Bromide are not soluble
 The Iodide ion is an excellent Nucleophile – A Lewis Base
with a pair of unshared electrons that seeks a positive
part of an atom
 Acetone is a non-polar solvent
 Alkyl Chlorides and Bromides would react with the
Sodium Iodide in an Sn2 reaction in which the Chloride &
Bromide ions are replaced with the Iodine atoms
 The reaction equilibrium is continuously forced to the
right as the NaCl & NaBr precipitate in Acetone
 As the reactivity of the Halide becomes less reactive
(Benzyl and Aromatic) precipitation ceases
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30
Organic Qualitative Analysis
Sodium Iodide in Acetone (Sn2 for Alkyl Halides)

Relative Halide reactivity for an Sn2 reaction is the opposite
of an Sn1 reaction, that is:
Vinyl > Methyl > Primary (1o) > Secondary (2o) >
Tertiary (3o) > Allyl  Benzyl  Aryl (Aromatic)
Note: Aryl (Aromatic) Halides are unreactive for both
Sodium Iodide (Sn2) and Silver Nitrate (Sn1) tests

Primary Alkyl Halides will give an immediate precipitate at
room temperature

Secondary Alkyl Halides will give a cloudy precipitate when
heated to 50oC and then cooled

Tertiary Alkyl Halides will also give a precipitate when
heated to 50oC and then cooled

Allyl, Benzyl, and Aryl Halides, like Chlorobenzene, will not
give a precipitate, even after heating
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31
Organic Qualitative Analysis
Sodium Iodide in Acetone (Sn2 for Alkyl Halides)
The Test


Add 6-8 drops of sample to 2mL of the 15% Sodium Iodide
(NaI) in Acetone solution and shake gently

Positive Test is a white or cloudy white precipitate

If a precipitate forms but disappears with mild shaking, the
instructor may suggest adding additional sample

Record the observed results at room temperature

If no precipitate forms, heat solution in a water bath
(maximum 50oC) for 1 minute and cool solution to room
temperature

Observe results

Record results for both room temperature and at 50oC
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32
Organic Qualitative Analysis
Bromine in Methylene Chloride (Simple Multiple Bonds)

Addition reaction of Bromine (Br2), a red liquid, to a compound
containing a double or triple bond produces a colorless
Dibromide

The double (or triple bond) must be sufficiently electron-rich
to initiate the reaction. Therefore, minimal electron
withdrawing groups (Deactivators), such as Carboxyl Groups
attached to molecule, would hinder the reaction

Unsubstituted Aromatic compounds do not react with the
Bromine reagent

Even if the ring has substituted activating groups (donate
electrons to the ring) the reaction would be a substitution and
not an addition
1/17/2015
33
Organic Qualitative Analysis
Bromine in Methylene Chloride

The Test

Dissolve 50 mg of unknown solid or 4 drops of
unknown liquid sample to 1 mL Methylene Chloride
(dichloromethane) or in 1,2-dimethoxy ethane .in a
test tube

Add 2% Bromine solution (Br2 & Methylene Chloride)
dropwise to the test tube and shake solution

The test is positive for presence of double or triple
bonds if 5 drops of Bromine decolorize the solution

If HBr is evolved, the test is negative indicating a
substitution reaction, instead of an addition reaction,
i.e., there are no double or triple bonds present
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34
Organic Qualitative Analysis
Potassium Permanganate (Baeyer) Test
(double or triple bonds)

Potassium Permanganate (KMnO4) is an oxidizing agent

It has a Purple color

Following the oxidation of an unsaturated compound, the
Permanganate ion is reduced to Manganese Dioxide
(MnO2), a brown precipitate
Note: Other easily oxidized compounds – Aldehydes,
some Alcohols, Phenols, and Aromatic Amines –
should be accounted for in your analysis
1/17/2015
35
Organic Qualitative Analysis
Potassium Permanganate (Baeyer) Test
(double or triple bonds)

The Test

Dissolve 25 mg a solid sample or two drops of a liquid
sample in 1-2 mL of one of the following solvents:

Water (if soluble, skip Ethanol & Dimethoxymethane)

95% Ethanol (if soluble, skip Dimethoxymethane)

1,2-Dimethoxymethane

Slowly add 1% aqueous solution Potassium Permanganate,
drop by drop, while shaking (usually just one drop works)

If the purple MnO4-1 ion is reduced to Manganese Dioxide
(MnO2), a brown precipitate, the test is positive for double
or triple bonds, but not Aromatic rings
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36
Organic Qualitative Analysis
Ignition (Aromaticity)
(=C-H bonds in Aromatic rings)

The Test

In a hood, place a small amount of the compound on a
spatula and place it in the flame of a Bunsen burner

Positive test is a sooty yellow flame
Note: The Sooty flame usually comes off fairly
quickly. Look for it moving quickly away and
upward from the yellow/blue flame area

1/17/2015
Positive test is indicative of a high degree of
Unsaturation and is probably Aromatic
37
Organic Qualitative Analysis
Acetyl Chloride (Alcohols)

Acid Chlorides react with Alcohols to form esters

Acetyl Chloride forms Acetate esters

This test does not work well with solid alcohols

Phenols also react with Acetyl Chloride and should be
eliminated prior to testing for Alcohols

Amines also react with Acetyl Chloride to produce heat
and also should be eliminated prior to testing
1/17/2015
38
Organic Qualitative Analysis
Acetyl Chloride (Alcohols)
The Test


Cautiously add 10-15 drops of Acetyl Chloride, drop by
drop, to about 0.5 mL of liquid sample

Positive test is evolution of Heat and Hydrogen
Chloride (HCl) gas

Addition of water will sometimes precipitate the ester,
further confirming the test
1/17/2015
39
Organic Qualitative Analysis
Lucas Test (Alcohols)

Primary Alcohols dissolve in reagent giving clear solution

Secondary Alcohols produce cloudiness after about 3-5
minutes. May need to heat slightly

Tertiary, Benzylic, and Allylic alcohols produce immediate
cloudiness; eventually, an immiscible Alkyl Halide
separates into a separate layer
1/17/2015
40
Organic Qualitative Analysis
Lucas Test (Alcohols)

The Test

Reagent – Conc HCL + Anhydrous Zinc Chloride

Lucas test does not work well with solid alcohols

Place 2 mL Lucas Reagent in small test tube

Add 3-4 drops of liquid sample; shake vigorously
1/17/2015
41
Organic Qualitative Analysis
Chromic Acid (Alcohols)

Chromic Acid (Cr+6) oxidizes Primary and Secondary
Alcohols to Carboxylic Acids and Ketones, respectively

Chromium (+6) is reduced to Chromium (+3)
The color change is from orange to green

Tertiary Alcohols do not react with Chromic Acid

Distinguish Primary & Secondary Alcohols from Tertiary
Alcohols
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42
Organic Qualitative Analysis

The Reaction
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43
Organic Qualitative Analysis
Chromic Acid (Alcohols) (Con’t)

The Test

Dissolve one drop of liquid sample or 10 mg of solid
sample in 1 mL pure Acetone

Add 1 drop of Chromic Acid reagent

Blue green color appears in less than 2 seconds for
Primary and Secondary Alcohols

Tertiary Alcohols do not produce blue-green color
within 2 seconds and solution remains orange
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44