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3.1 Experiment 3 Procedure

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  • Experiment 3. Aromatic Hydrocarbons

    1. Prepare a cuvette half to two-thirds full of hexane, wipe the sides with a Kimwipe and place in holder. Set up instruments using the parameters in Experiment 2. Obtain and store the dark spectrum and the reference spectrum of hexane.
    2. Add a drop of saturated naphthacene to the hexane cuvette and acquire a spectrum. Scale the graph such that you can resolve peaks, and continue to add naphthalene dropwise until peaks are very prominent. Save the spectrum and repeat the procedure for anthracene and naphthalene. It is not necessary to take a reference spectrum each time, but be sure to rinse the cuvette with hexane each time.
    3. Open your saved spectra. Right-click on spectrum graph on spectrum graph and select "Graph Layer Options." Under the Peaks tab, Select your spectral line form the Spectrum Source Selection window. Select the Show Peak Baseline Layer and press OK.
    4. At the bottom right corner of the graph, select the Peaks [clipboard_e03c1b1607aafe6d432fd07a2fa22d097.png] icon. The Peak Finding toolbar should appear directly above. Select the Configure [clipboard_ee9eba536f093f15fa92d62cb66074466.png] icon in the Peak Finding toolbar to open the Peak Properties window. Set the Baseline absorbance somewhat below the peaks of interest and increase the Minimum Peak Width until the number of peaks of interest and increase the Minimum Peak Width until the number of peaks found approaches the number of significant peaks you see on the graph. Click "Close" to exit the window.
    5. Using the Previous and Next Peak [clipboard_ed9e9224308d80f6c45c7f0ffe9063f3d.png] buttons, position the green cursor on each of the significant peaks and record the wavelengths (from the Wavelength box in the Peak Finding toolbar) in your notebook.
    6. Use the wavelength of the peak with the highest wavelength as the photon energy for the \( n=1 \longrightarrow n=2\) transition. Using the one-dimensional Particle-in-a-Box model, estimate the length, \(l\), of each compound. Plot the length as a function of the number of coordinated hydrocarbon rings.
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