Analysis of Trans-Anethole from Anise Seeds by NMR

Project C

Chem 361

Analytical Instrumentation

Spring 2006, second half

Analysis of trans-anethole from Anise Seeds by NMR

Task 1: Extract t-anethole from anise seeds via steam distillation.

Task 2: Acquire the FT-IR spectra of a standard t-anethole solution and on the anise seed extract. Identify and label the major vibrational stretches appearing in the FT-IR spectra.

Task 3: Acquire a GC-MS on the extract. Use the library to identify the primary peak.

Task 4: Use the Japanese website that contain the on-line searchable libraries of NMR, IR, and mass spectrometric data as a way of comparing your data for the standard and extracts to the published data. Compare the NMR spectra to results from Chem Draw and gNMR.

Task 4: Use a program called gNMR to simulate the NMR spectra of t-anethole at different magnetic field strengths. A free trial portion of this software has been downloaded to the UV computer in my lab.

Instructional guidelines:

Use Chem Draw to construct anethole and save the Chem. Draw file. Open the gNMR program. Import the Chem. Draw document. Go to “Settings” and then “Preferences”. Check to see what the Spectrometer Frequency (magnetic field strength) is set at. Record this value. Exit from “Preferences”. Click on the tab labeled “Spectrum” at the bottom of the table listing the J splitting constants. Put the cursor somewhere in the spectrum and go back into “Settings” and then to the tab under the “Settings” labeled “Spectrum”. Set the line width equal to “0.1 Hz”. This is a typical line width for proton NMR. Remember line width is a function of the T2 relaxation times. T2 relaxation is the fanning out of the magnetic field vectors in the x-y plane that occurs as a result of inhomogeneities in the magnetic field strength. Zoom in on splitting patterns for each of the proton signals. We can not print these out because this is a Trial software package that I downloaded off the web, and so it is “print” and “export” protected. As a result, I would like you to attempt to draw each splitting pattern in your notebook.

Changing the magnetic field strength:

Go to “Settings” and then “Preferences”. Check to see what the Spectrometer Frequency (magnetic field strength) is set it to 60 MHz, 200 MHz, 300 MHz, or 600 MHz. Record this value. Exit from “Preferences”. You must exit the program and start over after each time you reset the “Spectrometer Frequency”. You must now reset the linewidth to 0.1 Hz, each time. Attempt to draw each splitting pattern in your notebook for each magnetic field strength.

Also, write down the “j” values for each of the coupling listed in table. In your report discuss how the spectra change as you adjust the magnetic field strength.

Task 5: Manually simulate (draw) 2-D NMR plots for 1H COSY experiment and a 1H/13C HEPCOR experiment on t-anethole.