1. Organic Chemistry Lab 315 Fall, 2014

2. DUE DATES Today –At beginning of lab – Synthesis of Cyclohexene –At end of lab -- copy of laboratory notebook pages for today's experiment Next Week –Written summary of progress in identifying unknown, on a new continuation page in your notebook. See example in Manual, p. 70. In Two Weeks –Qualitative Analysis Report (two-week experiment)

3. Last Week’s Report You took an experimental IR. The report instructions said to attach it, along with a copy of a literature spectrum. The spectrum should have the important characteristic peaks marked. Separation Scheme: You need to review the concept, and the statements in the t-BuCl powerpoint, and the experiment itself. Look over your graded scheme to see what you did wrong. You will probably need to revise the cyclohexene separation scheme. To learn from your t-BuCl report, and to improve your cyclohexene report, you can take the cyclohexene report back, amend it, and return it to me by Thursday, 5:00 p.m. However, it must be turned in, complete, at the beginning of lab to take advantage of this offer.

4. In Lab Today Classes of compounds: hydrocarbons (alkanes, alkenes, alkynes, aromatic); hydrocarbyl halides (1 °, 2 °, 3 °, Ar); alcohols (1 °, 2 °, 3 ° ). Begin Qualitative Organic Analysis –Text p. 446ff –Manual p. 69ff All test solutions are ready for use. Dispose of all waste in designated containers. Continue the experiment next week.

5. Experiment Notes See Pavia p. 447 “How to Proceed- Option 1.” Receive a liquid unknown. Determine its boiling point (simple distillation) and refractive index. –Distill over ice. Use boiling stones. Do not distill to dryness. –Proper precision in refractive index. Room temperature will be given to you. Perform solubility and qual. tests on known compounds (see Manual table p. 73) and unknown.

6. Experiment Notes It is necessary to see both a positive and negative result for each test. It is necessary to perform all tests, even if you think you have already classified your unknown. You may perform the tests on knowns and your unknown with the other students who share your bench. –Remember, you are personally responsible for the outcome of all tests. Don’t let anyone test your unknown for you.

7. Experiment Notes When you have finished all the qual. tests, deduce what class of compound your unknown is, based on the qual tests, and justify it to me. (See Manual, p. 70.) –Only then will you be given permission to take an IR of your unknown. Store unknown in tightly capped vial (labeled with your name) for use next week.

8. Notes on Qualitative Analysis Tests After every test, read the “Discussion” in Pavia for an explanation of what a positive/negative test means. Tests for solubility –H 2 OGeneral idea of the number of carbons and/or presence of heteroatoms O, N, and S. –H 2 SO 4 Conc. H 2 SO 4 reacts with Lewis bases (compounds with non-bonding or pi electrons) such as alkenes, alkynes, some aromatics, alcohols. Heat or color change is designated “soluble”

9. Notes on Qualitative Analysis Tests Tests for Halides X = Cl, Br, I –BeilsteinUse a Bunsen burner. Copper wire + hydrocarbyl halide → CuX 2 (blue-green flame) –AgNO 3 /ethanolForms a AgX ↓ precipitate with hydrocarbyl groups that form stable carbocations (S N 1 reactivity: 3 ° ; 2 °, 1 ° with heating; aryl, vinyl NR) –NaI/acetoneForms NaBr or NaCl precipitate (S N 2 reactivity: 1 ° ; 2 °, 3 ° with heating; aryl, vinyl NR)

10. Notes on Qualitative Analysis Tests Tests for Unsaturation –Br 2 /methylene chlorideBromine reacts with  bonds of alkenes and alkynes. Red color of Br 2 disappears. Interpret immediately – eventually Br 2 reacts with sat’d. C-H –KMnO 4 Potassium permanganate reacts with  bonds of alkenes and alkynes. Purple color of permanganate changes to brown precipitate. Interpret immediately – eventually EtOH solvent oxidizes –Ignition Sooty yellow flame in Bunsen burner is an indication of unsaturation/aromaticity (incomplete combustion).

11. Notes on Qualitative Analysis Tests Tests for Alcohols –Acetyl chlorideAlcohols react with acetyl chloride to give acetate esters (CH 3 CO 2 R) and generate heat and HCl gas (test with moist litmus) DO THIS RXN IN THE HOOD! –Lucas test (ZnCl 2 /HCl)Forms a hydrocarbyl halide precipitate (S N 1 reactivity: 3 ° ; 2 ° after time; 1 °, aryl, vinyl NR). –Chromic acidOrange chromic acid turns green- blue when 1 ° and 2 ° alcohols are oxidized.

12. Notes on Qualitative Analysis Tests Set up a hot water bath using a large beaker of water on a hot plate. Use an eye-dropper and small grad. cylinder to count # drops in ml of liquid. I will assist in the Beilstein and ignition tests. Please be ready to conduct these tests in your group when I give you notice. Keep vial of unknown in a small beaker so it doesn’t tip over and drips are contained.

13. Weekly Clean-up Lozano Postol