Interactive Spectra

Shown below are six sample interactive spectra: UV, MS, IR, ¹H NMR, ¹³C NMR | DEPT and HETCOR. All spectra have a cursor that displays the abscissa value. Additional interactivity (i.e. drag / read a ruler) is present in some spectra.

All the spectra except the UV are of Eugenol (Clove Oil). Chem21Labs has developed an Organic lab where students work in groups of four to isolate Clove Oil (Steam Distillation) and in the same groups they complete a Clove Oil "dry lab" where they must answer questions using the MS, IR, ¹H NMR, ¹³C NMR | DEPT and HETCOR spectra. Each instrument gives the students a "piece of the puzzle" . . . .

1. MS gives the molecular mass.
2. ¹³C NMR gives the number of carbons. These two pieces of information provide the molecular formula.
3. Next, the degrees unstaturation are calculated from the molecular formula.
4. From the formula and degrees unsaturation, 20 possible structures (right) of clove oil are given to the students. For the rest of the lab, students use provided spectra to eliminate structures from this list.
5. IR gives information about the functional groups present and permits the elimination of some structures.
6. The fact that clove oil has no plane of symmetry permits the elimination of more structures.
7. The ¹H NMR reveals the presence of aromatic and vinylic hydrogens and permits the elimination of more structures.
8. The ¹³C NMR reveals the number of aromatic / vinylic carbons and permits the elimination of more structures.
9. The ¹H NMR, ¹³C NMR, DEPT and HETCOR are used together to complete the final identification of clove oil.
10. Post-lab Questions:
    • Which peak in the ¹H NMR will disappear on addition of D₂O? Explain.
    • The solubility of the isolated clove oil (from steam distillation) was determined in water, 5% NaOH and 5% NaHCO₃. Are the solubility results consistent with the structure of clove oil? Explain.

Ultraviolet (UV) Spectroscopy

Mass Spectroscopy (MS)

Students mouse over the UV spectrum of Carbaryl / 1-Naphthoxide to determine λ_max (the x and y crosshair coordinates are shown on the right). The λ_max value is reported in the lab report and feedback is given when it is automatically graded.

Students mouse over the MS spectrum to determine the mass of the molecular ion, the mass of a fragmented ion, or the mass of the base peak. Any of these masses can be reported in the lab report and automatically graded.

InfraRed Spectroscopy (IR)

¹H NMR

Students mouse over the IR spectrum to determine the wave numbers (cm^-1) of the peaks indicated (1, 2, 3). A match of the wave numbers to the functional group absorbing at that frequency is best graded where the student selects the functional group's name from a drop-down (choice) menu.

Students mouse over the ¹H NMR spectrum to determine the chemical shifts of the various proton absorptions. The integration traces can be measured using the draggable ruler or the y value of the mouse coordinates. These values and the corresponding number of Hydrogens present in each absorption can be reported in the lab report and automatically graded.

¹³C NMR | DEPT

2D NMR - HETCOR

Students mouse over the ¹³C NMR spectrum to determine the chemical shifts of the various carbon atoms. Clicking the DEPT-90, DEPT-135 and ¹³C NMR buttons will cycle through the various spectra. This information is primarily used to identify an unknown organic compound.

Two-dimensional NMR spectra provide information not available in proton or carbon NMR. The HETCOR experiment "matches" the carbon absorption in the ¹³C NMR spectrum to its attached proton in the ¹H NMR spectrum.