NMR Quiz in organic chemistry
Trending is an amino idol that is the active ingredient in the antihistamine Salaamed. Mass spectral analysis of trending shows a molecular ion at m/z = 471 and a peak at m/z = 472 which is 35. 5% the height of the molecular ion. Trending is known to contain C, H, O and N. (a) Suggest five molecular formulas for trending. (b) Trending has an even number of carbons and contains nine double bonds and four rings. Based on this additional information, what is the formula for trending? (c) Explain the origin of the peak at m/z = 472. (12 puts. ) 9.
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Explain why all protons in a molecule do not absorb ref (radio frequency) energy at the same frequency. 10. Answer the following questions. (5 puts. ) (10 puts. ) (a) How many groups of peaks do you expect for the 1 H NORM spectrum of styrene oxide? Styrene oxide (b) Draw a tree diagram for the proton-2 (H2O) signal. The relative coupling constants should be expressed in your diagram. 11. Propose a structure for compound A, which has M+ = 86 in its mass spectrum, an IR absorption at 3400 CM-l , and the following ICC NORM spectral data: (6 puts. ) Compound A Broadband-decoupled ICC NORM: 6 30. , 31. 9, 61. 8, 114. , 138. 4 DEPT-90: 6 138. 4 DEPT-135: positive peak at 6 138. 4; negative peaks at 6 30. 2, 31. 9, 61. 8, 114. 7 12. Refer to the mass spectrum of a hydrocarbon shown below to answer the following questions. (12 puts. ) (a) What peak represents the molecular ion (M+)? (b) What peak represents the base peak? (c) Propose plausible molecular structures for the hydrocarbon. (d) Propose structures for the fragment ions at m/z = 57, 43, and 29 based on your answer 13. Match a structure from the list below to the following IR spectra. Place the letter f the structure in the blank to the left of the spectrum. TTS. ) (10 14. The following 4-term-biotechnology can have both CICS and trans storerooms. (a) Draw the most stable conformation of each isomer. (b) The two isomers show different II NORM spectra, particularly for the CLC protons (the proton adjacent to the hydroxyl group). Predict which of the CLC protons appears at more dwindled than the other. How can you explain this? (Hint: the ring current of cyclopean) (c) The hydroxyl hydrogen splits into a doublet in the case of a pure sample, whereas it appears as a broad singlet in other cases. How can you explain the phenomena? 5. To answer the following questions, consider the data and II NORM spectrum below: The mass spectrum of this compound shows a molecular ion at m/z = 1 13, the IR spectrum has characteristic absorptions at 2270 and 1735 CM-l, and the ICC NORM spectrum has five signals. (a) Based on the mass spectral data and the IR data, what functional groups are present in this compound? (b) Describe the signal at 0 3. 5 pimp in terms of its integration, splitting pattern and chemical shift. (c) What is the significance of the ICC NORM data? (d) Propose a structure for this compound.