Qualitative Analysis Unknowns ***Cyclohexane Butyl bromide Butyl alcohol *Tertbutyl alcohol **Tertbutyl chloride Allyl alcohol Cyclohexene Allyl chloride *Tertbutyl alcohol may be tertamyl alcohol. Reactions are the same. ** Tertbutyl chloride may be tertamyl chloride. Reactions are the same. *** Cyclohexane may be hexane. Reactions are the same. General Goal: to identify 8 unknowns through chemical tests. You may carry out the tests in any order that you wish. A scheme is included in this handout which may help you in deciding the identity of the unknowns. You are allowed to take the boiling point of two unknowns. Alkene and alcohol test 1) Cold concentrated sulfuric acid: Place a little concentrated sulfuric acid in a test tube. Chill the tube in an ice/water bath. POSITIVE: Add a few drops of a compound that you know will be positive for sulfuric acid carefully down the side of the test tube. NEGATIVE: To a new sulfuric acid tube, add a few drops of a compound that you know will be negative for sulfuric acid carefully down the side of the tube. UNKNOWN: Finally, to a new sulfuric acid tube, carefully add drops of the unknown down the side of the tube. WARNING: One of the unknowns reacts VIOLENTLY with concentrated sulfuric acid. Be very careful with the unknowns and sulfuric acid. Compare your unknown to your two knowns and determine if your test is positive or negative. CLEANUP: Carefully mix all of the sulfuric acid test tubes together, neutralize with sodium bicarbonate, and pour down the drain.
Alkene test 2) omine: WARNING: omine WILL burn if it gets on your skin or in your lungs. Place a little of a 5% bromine (v/v) in methylene chloride solution in a test tube. POSITIVE: Add a few drops of a known that you know will be positive for the bromine test down the side of the test tube. NEGATIVE: To a new bromine solution, add a few drops of a known that you know will be negative for the bromine test down the side of the test tube. UNKNOWN: Finally, to a new bromine solution, add a few drops of the unknown. Compare your unknown tube to your two control tubes and determine if your test is positive or negative. CLEANUP: Mix all bromine test solutions together and discard in a halogenated waste container. Primary halide 3) Acetonic sodium iodide: Place a little of a 15% (w/v) solution of sodium iodide in acetone in a test tube. POSITIVE: Add a few drops of a compound that you know will be positive for the sodium iodide test. NEGATIVE: To a new sodium iodide solution, add a few drops of a compound that you know will be a negative for the sodium iodide test. UNKNOWN: Finally, to a new sodium iodide solution, add a few drops of your unknown. Your unknown may not be soluble in acetone and may form two layers. This is neither a positive or negative test. Compare your unknown to the two control tubes and determine if your test is positive or negative. CLEANUP: Add all of the sodium iodide test tubes together and discard down the drain. Tertiary halide 4) Ethanolic silver nitrate: Place a little of a 2 % (w/v) solution of silver nitrate in ethanol in a test tube POSITVE: Add a few drops of a compound you know will be positive for the silver nitrate test solution. NEGATIVE: To a new silver nitrate solution, add a few drops of a compound you know will be negative for the silver nitrate solution. UNKNOWN: Finally, to a new silver nitrate solution, add one drop of the unknown. Compare your unknown to the two control tubes and determine if your test is positive or negative. CLEANUP: Add all of your silver nitrate test solutions in a waster beaker for silver nitrate. Alcohol test
Alcohols react differently with many reagents (Jones reagent, TCICA reagent, Ceric ammonium nitrate, Lucas test reagent) depending upon whether they are primary, secondary, or tertiary. We will use H since we have a tertiary and primary alcohol whose identity needs to be determined. A tertiary alcohol should react with H rapidly to form a second layer. POSITIVE: Mix tertamyl alcohol with concentrated H in a test tube. Observe if two layers form. NEGATIVE: Mix 1butanol with concentrated H in a test tube. Observe if two layers form. UNKNOWNS: Mix each unknown separately with H in a test tube. Match up the unknowns with the positive and negative tests. CLEANUP: Mix all of the test tubes together in a separatory funnel. Separate the organic layer from the H layer. Neutralize the H layer and pour down the drain. Put the organic layer in the waste bottle. Cyclohexene/Allyl alcohol test CYCLEXENE: Mix cyclohexene with concentrated H 2 SO 4 in a test tube. Observe reaction BUCS. ALLYL ALCOL: Mix Allyl alcohol with concentrated sulfuric in a test tube. Observe reaction CBU. UNKNOWNS: Mix each unknown separately with H 2 SO 4 in a test tube. Match up the unknowns with the reactions. CLEANUP: Mix all of the test tubes CAREFULLY together. Neutralize the solution CAREFULLY IN THE OD and pour down the drain. Flow chart for determining the identity of each unknown is on next page.
H 2 SO 4 NaI/Acetone 2 /C 4 Compounds negative for bromine but positive for sulfuric acid Reaction with H
Compounds negative to sulfuric acid and negative to sodium iodide/acetone Silver nitrate _ Compounds positive for sulfuric acid and positive for bromine Sodium Iodide/ Acetone _ Compound positive for sulfuric acid, positive for bromine and negative for sodium iodide /acetone Reaction CBU H 2 SO 4 Reaction BUCS