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Chemistry 822, 1998, Dr. Hunter
Laboratory Assignment #5 and Lab Exam Part A
Basic Operation of the 400 MHz NMR Spectrometer
Part I. 1H NMR. Load the 1% 3-heptanone standard sample into the spectrometer and lock and shim the spectrometer.
(a)Save you shim settings as C822.yourfirstname.6Ia
(b)Set up for a 1H NMR spectrum with one transient and an acquisition time of 20 seconds. Collect the spectrum and save it in your 3-heptanone directory as basic1H3heptanone and then reload it.
(c)Plot out the full FID with a time scale and basic parameters. What is the maximum acquisition time actually required? [Write it on the FID plot.]
(d)Fourier Transform the spectrum, reference it, and plot the full spectrum with scale and full parameters.
(e)Measure the resolution of several representative lines and write them on the spectrum.
(f)Narrow the spectrum and make several plots: one with wp=8p and sp=-0.5p; one that just includes all peaks (but is an even multiple of ppms [Note: this is the only one that needs to be integrated]): and one that just includes one or two peaks (for this make the width of plot equal to some even multiple of 10 Hz (the same in all sub spectra) and put the scale in Hz and plot peak positions).
(g)For your most complex multiplet, sequentially set line broadening to first 1 then 2 then 5 Hz doing a weighted Fourier Transform each time and plotting the result each time.
(h)Write a short discussion of the effects of acquisition time and line broadening on 1H spectra properties based on our discussions in class and your lab results.
Part II. 13C NMR. Load the 30% menthol standard sample into the spectrometer and lock and shim the spectrometer.
(a)Save you shim settings as C822.yourfirstname.6IIa
(b)Set up for a 13C NMR spectrum with 128 transients, a spectral width of 400 ppm, and an acquisition time of 5 seconds. Collect the spectrum and save it in your menthol directory as basic13Cmenthol and then reload it.
(c)Plot out the full FID with a time scale and basic parameters. What is the maximum acquisition time actually required? [Write it on the FID plot.]
(d)FT the spectrum, reference it, and plot the full spectrum with scale, peak positions, and full parameters. Write on the spectrum what sweep width would have been OK.
(e)Move the sweep width to this choice (make it an even multiple of 20 or 50 ppm) and then recollect it for 128 transients, the new sweep width, and the better acquisition time. Save this in your menthol directory as basic+13Cmenthol and then reload it. Plot out the full FID with a time scale and basic parameters. FT the spectrum, reference it, and plot the full spectrum with scale, peak positions, and full parameters.
(f)Measure the resolution of several representative lines and write them on the spectrum.
(g)Narrow the spectrum and make several plots (include one plot that just includes all of the peaks and the solvent reference and one plot that just includes the compound peaks (make each of these an even multiple of 10 ppm)).
(h)Plot your peak with the lowest chemical shift (with a width of plot of 10 ppm) with a scale in Hz, measure its line width, and write this on the plot.
(i)Plot the region around the solvent triplet twice with a width of plot of some multiple of 1 ppm. In the first, plot set the vertical scale equal to 160. In the second, set the vertical scale into some even multiple of 160 that makes these peak heights between about 50 % and 75% of the page height.
(j)Write a short discussion of the effects of acquisition time and sweep width on 13C spectra properties based on our discussions in class and your lab results.
Note:All NMR spectra should include the full parameter list, and a scale of some sort, and a vertical scale of 160 unless there is a special reason not to do this.
C:\TEACHING\822\822w98\Chemistry 822.W98.Lab Exercises\Laboratory Assignment #5.W98.001.doc