2.3: Day 3 Procedure - Instrumental Analysis

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Day 3: Instrumental Analysis* of the Limonene and Carvone

Be sure to record details about the instruments used manufacturer model (number) for inclusion in your report.

Part D. Melting Point of Semicarbazone Derivative

Take the melting point of the dry solid semicarbazone derivative and record the yield. If it is necessary to recrystallize the semicarbazone derivative, you may do so from an ethanol/water mixture. Repeat measurement of the melting point to verify the success of the recrystallization.

Part E. Measurement of Optical Rotation by Polarimetry

Make up 10 mL of a 1.5-3% (w/v) solution⁶ of your semicarbazone in ethanol. Add this to a polarimeter tube obtained from the stock room. Measure the optical rotation of the semicarbazone derivative solution in the polarimeter following the procedure demonstrated by your TA. This technique is very dependent on the interaction of light with a clean sample. Be sure the cell is clean. If there is any particulate matter or cloudiness to the solution filter it first. Finally check that no air bubbles have formed which will also interfere with the analysis.

Part F. Infrared spectroscopy of limonene and carvone

Run infrared spectra following procedure demonstrated by your TA, of the limonene and carvone fractions obtained by distillation. The infrared spectrum may be run using neat liquid on salt plates or as in this experiment, by spotting several drops of liquid (disposable pipet!) on the window area of an IR card. If the peak absorbances are low, place an additional few drops of the limonene or carvone on the IR card, and rerecord the spectrum.

Part G. Refractometry

Measure the refractive indexes of pure limonene, pure carvone, original oil, limonene fraction and carvone fraction following the procedure demonstrated by your TA. Calculate x_carvone, and compare with the GC data.

Footnotes

⁶ Approximately 0.15 g to 0.3 g sample in 10 mL of solution