Identification of an Unknown O Compound

Identification of an Unknown Oxygen-Containing Compound

Summary of test procedures: read the text for complete instructions.

Ignition test, Page 574

Place 3-4 drops of unknown on a clean watch-glass, and ignite them. Observe the color of the flame. A blue flame usually indicates oxygen. A sooty flame usually indicates C=C’s or benzene rings.

Water-Solubility, Page 577

4-5 drops of unknown + 3 mL of water, shake: is it dissolved?

2,4-DNPH test, C-11 & D-3, p. 601

Dissolve 4-5 drops of unknown in 4 mL of 95% ethanol, then add 3 mL of 2,4-DNPH reagent. Cool, filter, wash with water and NaHCO3 solution, then recrystallize from ethanol.

Chromic acid Test, C-9, p. 585-6

Add 1-2 drops of unknown to 1 mL of reagent acetone in a small test tube. Add 1 drop of chromic acid solution. For comparison, add 1 drop of chromic acid solution to 1 mL of acetone in another small test tube.

Iodoform test, C-16, p. 590-1

Add 3 drops of unknown to 2 mL of water in a large test tube. Add 1 mL of 3M sodium hydroxide solution. Add a dropper-full of iodine-KI solution. If a yellow ppt. forms, it is a positive test. See text if no yellow ppt. forms.

3,5-dinitrobenzoates, D-1, p. 600 – Dry alcohol first with Na2SO4 or MgSO4.

0.2 g 3,5-dinitrobenzoyl chloride + 4-5 drops of alcohol in a medium test tube, heated in a small flame just enough to maintain in a liquid state for 5-10 minutes. Cool, break up with a spatula, add 4 mL of sodium carbonate solution, heat in a boiling water bath for a few minutes. Cool, filter, wash with water. Recrystallize from ethanol or ethanol-water.

-Naphthyl urethanes, D-2, p. 600-1 – Dry alcohol first with Na2SO4 or MgSO4.

Mix 5-drops of alcohol with 5 drops of -naphthyl isocyanate in a medium test tube. If no reaction takes place immediately, heat in a boiling water bath for 5-15 minutes. Cool, filter, recrystallize from heptane.

Semicarbazone or Oxime, D-4 and D-5, p. 602 2

Mix 0.20 g of semicarbazide HCl or hydroxylamine HCl, 0.30 g of sodium acetate, 2 mL of water and 2 mL of 95% ethanol in a large test tube. Add 0.20 g of unknown. Cork and shake for a couple minutes. Cool and see if crystals form. If not, heat in a boiling water bath for about 5 minutes, then cool and filter. Wash with cold water, then recrystallize with ethanol or ethanol- water mixture.

Report format

1. Title Page

a. Descriptive title with between 10-25 words. b. Course and section numbers. c. Dates the experiment was performed. d. Your name.

2. Body of the report. a. Unknown number b. Boiling range c. Odor Test Observation Conclusion d. Ignition Test, p574 e. Solubility in water f. Results of 2,4-DNPH test g. Results of Chromic acid test h. Results of Iodoform test i. Important peaks from the IR j. Functional Group indicated by the above tests Derivative Melting Point Range k. Derivatives Made

3. Questions

a. How did you determine what functional group you had for your answer to 2j, above? Explain how you used the data. 3 b. What compounds were on your initial list of possibilities (Detection of Structural Features, p. 345)? Why did you include them? c. How did you determine the structure of your unknown? Walk me through your thinking process, explaining how you used the data you had. Don’t say things like, “The NMR spectra told me I had 2-propanol.” Explain how you used the data. d. Attach your proton NMR spectrum to the report. Draw the structure of your compound on the NMR spectrum, and indicate which sets of peaks correspond to which hydrogens in the structure by drawing arrows from the hydrogens to the peaks. Explain any coupling patterns in the spectrum. e. Attach your carbon NMR spectrum to the report. Draw the structure of your compound on the NMR spectrum, and indicate which peaks correspond to which carbons in the structure by drawing arrows from the carbons to the peaks.