1. 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

2. 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

3. Organic Qualitative Analysis
The Tests – Compound Classes
Test Compound Class
Solubility Relative to H2O & H2SO4 All
Density Relative to H2O All
Beilstein (Flame) Halides
Silver Nitrate/Ethanol Alkyl & Aryl Halides
Sodium Iodide/Acetone Alkyl & Aryl Halides
Bromine/Methylene Chloride Unsaturated C=C CC
KMnO4 (Baeyer Test) Unsaturated C=C CC
Ignition Aromaticity C=C
Acetyl Chloride Alcohols
Lucas Test Alcohols
Chromic Acid Alcohols

4. Organic Qualitative Analysis
The Tests – Test References
(Pavia (3rd ed) – GMU Version or Pavia Main text as indicated)
Test Page No.
Solubility Relative to H2O & H2SO4 p
Density Relative H2O p
Beilstein (Flame) p
Silver Nitrate/Ethanol P
Sodium Iodide/Acetone p. 158 Pavia Main Text
Bromine/Methylene Chloride p
KMnO4 (Baeyer Test) p
Ignition p
Acetyl Chloride p. 585
Lucas Test p. 585
Chromic Acid p

5. Organic Qualitative Analysis
Elements of the Experiment
Two week experiment
Pre-lab must cover both weeks
Week I
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

6. Organic Qualitative Analysis
Elements of the Experiment (Con’t)
Week I (Con’t)
Chemical Tests for known compounds
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)

7. 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)

8. 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

9. Organic Qualitative Analysis
Elements of the Experiment (Con’t)
Week II
Continuation of known compounds
Tests
Silver Nitrate/Ethanol Alkyl & Aryl Halides
Sodium Iodide/Acetone 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.

10. Organic Qualitative Analysis
General Notes
Dangerous Chemicals – Acetyl Chloride, Conc H2SO 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)

11. 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
Be sure to obtain a good positive result for each test; repeat the test until a good positive result is obtained

12. 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

13. 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
Add test reagent
Add compound to be tested; shake mixture
Heat reaction mixture if specified in test directions

14. 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

15. 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
Note: For tests not involving temperature differentials, leave the 50oC & 100oC blocks blank or just remove the columns
Compound
Observation
(Rm Temp)
50oC
100oC
Positive(+) /
Negative (-)
Unknown
Leave Blank
Known #1
Known #2
Known #3

16. 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

17. 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 = atmospheres
= psi (pounds per square inch)
= in Hg (inches of mercury) = mm

18. 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 ( 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

19. Organic Qualitative Analysis
Typical Distillation Setup

20. 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

21. 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

22. 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
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

23. 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

24. 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

25. 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

26. 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 (more dense)
Solubility of a Hydrocarbon in water indicates 4 or less carbons

27. 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

28. 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)

29. 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
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

30. 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

31. 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

32. 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

33. 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

34. 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

35. 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

36. 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

37. 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
Positive test is indicative of a high degree of Unsaturation and is probably Aromatic

38. 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

39. Organic Qualitative Analysis
Acetyl Chloride (Alcohols)
The Test
Cautiously add 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

40. 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

41. 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

42. 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

43. Organic Qualitative Analysis
The Reaction

44. 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