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Chem 464 Fall 2024
Assignment 3
Due: November 19, 2024
1. Following are the 500 MHz 1H NMR spectra at various temperatures of the compound drawn below.
(a) Account for the difference in appearance of the spectra at room temperature and at 120 °C.
(b) Assign each of the singlets observed at higher temperatures to protons in the compound.
(c) Calculate the activation energy for the exchange process observed.
2. For the following pairs of compounds, show how one might be able to distinguish them using IR spectroscopy. Be sure to include estimates of band positions and intensities as appropriate. If IR spectroscopy is not sufficient to unequivocally distinguish between the compounds, propose another spectroscopic method (along with expected spectral differences) that might be more suitable.
3. Identify the following compounds based on the spectral data presented. If it is not possible to
determine a precise structure, propose alternative isomers. Be sure to show your rationale clearly. The scale is cm-1 for IR spectra and ppm for NMR spectra.
(a) C6H10O
(b) C6H12O2
(c) C6H6BrN
(d) C4H6O2
(e) C9H8O
(f) C7H5FO
4. Following are 1H NMR (CDCl3, 300 MHz with expansions), 13C NMR (CDCl3, 75 MHz, CPD) and DEPT-135 spectra of a compound C12H12N2O7. Determine the structure of this compound, including any stereochemistry, and assign each of the protons. Rationalize your assignments with chemical shift and coupling arguments. You will need to look at coupling constants in order to assign stereochemistry.
5. Following are the 13C NMR (CDCl3, 50 MHz) and 1H NMR (250 MHz, CDCl3) spectra of a
compound C9H14O3. Determine the structure of this compound and give the Pople notation for the spin systems in the 1H NMR spectrum.
6. One final unknown (for this assignment): A compound C16H17NO2 whose IR, 1H NMR (250 MHz, CDCl3) and 13C NMR (63 MHz, JMODXH, CDCl3) spectra follow. As usual, clearly show your reasoning. Be sure to include rationalizations for the appearance of the signals labelled A, B, and C in the 1H NMR spectrum.
