Experiment 8, Pavia, et al
Your goals in this experiment will be to analyze (+)- and
(-)-carvone by polarimetry, refractometry, IR, and NMR spectroscopy. You
may also observe the odor of the two natural stereoisomers of carvone. We
will omit anything in Expt. 8 having to do with gas chromatography (GC)
and boiling point determination. The IR and 13C NMR spectra will be
provided for you at the stockroom window (you will not be able to run
these instruments to obtain your own data).
1) There is no "Main Reaction" or "Separation Scheme" for this experiment.
Instead, in addition to stating the goals of the experiment in the usual
location, provide a brief overview of the procedures to be conducted.
2) Measure the optical rotation of neat (pure, undiluted) samples of both
carvone stereoisomers using the polarimeter (black device resembling a
small telescope in the Open Lab). Read Technique 17, Pavia, for
instructions. Calculate the specific rotation for both samples. The
polarimeter sample cells are pre-filled for your use and are one decimeter
(dm) long. The samples of carvone are neat (without solvent). The
concentration of a neat sample in g/mL is equivalent to its density. Make
multiple determinations of your observed rotation and average them to
obtain the final experimental value.
3) Measure the refractive index of each carvone isomer using the
refractometer in the Open Lab. Instructions for this are also found in
Pavia et al. Include a temperature correction if necessary. Make
multiple determinations of the refractive index and average them to obtain
the final experimental value.
4) Pick up from the stockroom window the handout with the 13C (carbon-13)
NMR spectrum and IR (infrared) spectrum of carvone. For the 13C NMR
spectrum, assign as many of the peaks as possible in the spectrum to the
specific carbons from which they arise in the structure of carvone. It is
helpful to draw a structure of the molecule whose spectrum is being
interpreted and label atoms in the structure with letters that correspond
to letters given to peaks in the spectrum.
For the IR spectrum, identify the specific absorptions in your spectrum
that correspond to the stretching frequencies of the carbonyl group,
alkene carbon-carbon bond, and C-H stretches for both hydrogens bonded to
sp3 carbons and those attached to sp2 carbons.
It will be helpful to use Tables 13.2 and 13.4 in Solomons and/or
information in Pavia on the interpretion of IR and 13C NMR spectra. Your
interpreted spectra should be submitted with your lab notes for grading.
Since it is generally advisable not to mark directly on an original piece
of data (in this case the copy I provide you), I suggest photocopying the
spectra and marking your interepretations on the working copy. Tape a
copy of the spectral data in your notebook.
5) Answer questions 1-4 in Pavia, as assigned in the syllabus. Disregard
the mention of limonene in question 1.
3/97 CBF
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Craig B. Fryhle, Ph.D. Office 206-535-8314 FAX 206-536-5055
Associate Professor Email fryhle@u.washington.edu
Department of Chemistry URL http://rainier.chem.plu.edu/fryhle.html
Pacific Lutheran University
Tacoma, Washington 98447 ^ ^ ^ ^ ^ ^
^ ^^^ ^^^^^^^ ^ ^^^ ^^^^ ^^^ ^
^^^^^^^^^ ^^^^^^^^^ ^^^^^^^^^^^^^^^ ^^^^^^^^
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^