Nuclear Magnetic Resonance (NMR) is one of the fundamental analytical techniques used in organic chemistry to help identify the structure of unknown compounds. Because of the time and expense associated with the measurement of actual spectra, NMR is not typically available in the undergraduate organic laboratory. In the Virtual ChemLab simulation, 1H and 13C NMR spectra can be measured on the solution contained in any flask or the separatory funnel after a reaction mixture has been worked up. The spectra that are shown in the simulation are actual spectra for the 1H NMR and predicted spectra for the 13C NMR based on sophisticated prediction algorithms. 1H NMR spectra were taken on a 300 MHz instrument, and 13C NMR spectra were simulated as if taken on a 125 MHz instrument.
An NMR is measured by clicking on the NMR machine and dragging the small NMR tube to the solution of interest. The control screen or the buttons next to the screen on the NMR instrument can be used to switch between 1H NMR and 13C NMR. The resulting NMR spectra will be displayed in its own window, and to better identify splittings and crowded regions, a region of the graph can be expanded by clicking and then dragging a box over the desired area. To go back to full scale, click the Zoom Out button. For 1H NMR, peaks are identified by numbers from left to right, and an integration of the area below each peak is given in the tables below the spectra (up to 15). For 13C NMR, mousing over the peaks will provide the exact chemical shift for the peak. NMR spectra of solutions containing mixtures are also allowed with the peak areas adjusted for the relative concentrations. The OK button closes the NMR window, and the Save button saves the NMR to the lab book.
A spectra library containing over 700 spectra is available by clicking on the Spectra tab. When an NMR spectrum is obtained from the library, the IUPAC and common name for the compound and several physical properties are listed in the text boxes above the spectra. Spectra from the library can also be saved to the lab book. When a spectrum is generated from the lab bench, the text boxes are left empty since the spectrum is an unknown. The IUPAC and common name text boxes can be used to write notes about the spectra that will be attached to the spectra if saved.