CHEM 350 - Principles of Organic Chemistry I ......................................Prof. T Nalli, Fall 2009, Winona State University Experiment #3 - Identification of a Liquid Unknown Using IR and NMR Spectroscopy References: Smith, Chapter 13-14, Mohrig, et. al, Techniques 18 and 19. Pre-Lab Assignments: 1. The pre-lab plan part of the lab notebook is not necessary for this experiment. 2. Install and unlock the JEOL Delta software on your laptop
Overview: You will obtain 13C NMR, 1H NMR, and IR spectra of a liquid unknown. From these and the molecular weight, which will be provided by the instructor, you will be able to deduce the identity. Safety
Precautions - Most of the unknowns are classified as irritants, some are also toxic, and some have disagreeable odors. As always it is best to minimize exposure to possibly harmful substances by wearing gloves while handling samples and carrying out all transfers in a hood. CDCl3 has harmful fumes. Avoid breathing it and dispense it in a fume hood.
Procedure: Please note that you will be expected to obtain IR and NMR spectra many times in this course and I expect you to eventually be able to obtain them unassisted. Therefore, you should take note of the procedures you use in this lab. 1. Obtain an unknown from the instructor and record the unknown number in your lab notebook. Carefully record any observations you can make of the unknown. 2. Obtain the IR Spectrum
B. Obtaining the NMR Spectra
General Instructions for Using Delta 1. Choose "Process 1D" under the Processors menu and open the file by using the file menu, clicking on the 2. To convert the data to a useable form you need to Fourier Transform it 3. To annotate the spectrum with peak chemical shifts use the "Auto Peak Pick" icon, 4. Zooming in is accomplished by clicking and dragging on the spectrum. Clicking and dragging in the gray area below the x-axis just zooms in along the x-axis with the y-axis remaining at full scale. Use the keyboard key: "BackSpace" to revert to the previous (unzoomed) view. 5. Print the spectrum by simply printing on the icon that looks like a printer and selecting the desired printer from the scroll list. Report: A full report is not required for this lab. Instead I expect you turn in fully-labeled printouts of your three spectra. Label each spectrum with your group name(s), course number, section number, and experiment number. The structure of the molecule should be written prominently on each spectrum. For the C-13 spectrum label all sets of equivalent carbons a, b, c, etc. and then label the peaks in the spectrum a, b, c, etc. to show which carbons in the molecule are represented. Also label any extraneous peaks such as the CDCl3 solvent peak in the C-13 spectrum and impurity peaks.The peaks should also be labeled with chemical shift (use Delta for this and make sure there are no extraneous chemical shift labels for "nonpeaks"). For the proton NMR label the Hs in the molecule and then label the resonances accordingly. As with the C-13, label any extraneous peaks and make sure the peaks are labeled with their chemical shifts. The proton NMR should also be labeled with integration values that have been normalized to show the number of Hs represented by each. (The instructor will demonstrate how to do this in a lecture.) In the IR spectrum label all important functional group peaks. For peaks in the fingerprint region label the major ones with the corresponding wavenumber value for the same peak in a literature spectrum. Two good places to look for literature spectra are the Fiveash Database and the NIST WebBook, both available through the library at http://www.winona.edu/library/eref/chem.html#chemspec. There is also a bound version of the Aldrich Library of IR Spectra available in the IR lab.
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