Week_4.1_PurpleBook_Answers

Week_4.1_PurpleBook_Answers - 89 Homotopic Enantiotopic...

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Unformatted text preview: 89 Homotopic, Enantiotopic, Diastereotopic Week 4 1. For each of the following molecules, identify (if possible) one pair of homotopic hydrogen atoms, one pair of enantiotopic hydrogen atoms, and one pair of diastereotopic hydrogen atoms. (Not all types of pairs can be found in each case!) H D D H Br Br vs. Br Br same: homotopic Br Br Br H Br D Br vs. Br D H Br enantiomers: enantiotopic Br Br Br D H Br has no diastereotopic pairs of H's Br H vs. H D Br Br enantiomers: enantiotopic vs. D D D H H same: homotopic vs. H D H H D D same: homotopic vs. has no diastereotopic pairs of H's D H H enantiomers: enantiotopic vs. D D enantiomers: enantiotopic H vs. H D Cl Cl Cl H D Cl H D Cl D H Cl Cl H Cl Cl H D Cl H D same: homotopic vs. Cl Cl same: homotopic vs. Cl D H Cl diastereomers: diastereotopic vs. Cl H D D Cl enantiomers: enantiotopic vs. Cl Cl enantiomers: enantiotopic 90 Infrared Spectroscopy Week 4 1. Match the spectra below with the following compounds. (One of the compounds does not match any of the spectra.) Circle any spectral features that you used to assist in the identification. O OH C: B: O A: H A: B: C: 91 NMR Spectroscopy: Chemical Shifts Week 4 1. By analyzing the chemical shifts and integrations, assign the proton NMR peaks to the protons in each molecule. c c a b b a c a b b OH c a OCH3 c a a f d b e a e f d 92 NMR Spectroscopy: Spin/Spin Splitting Week 4 1. Analyze the multiplets in the following proton NMR spectrum, and explain the observed splitting. Then write in the "integral" you expect for each multiplet. 3H c c a 2H b CN a 2H b 2. Below is a portion of the proton NMR spectrum of styrene, showing only the peaks for the two terminal protons (indicated below as Ha and Hb). Given the list of coupling constants (below), assign the peaks to the two protons. Explain the reasoning behind your assignment. (For "extra credit," what would the other alkene proton look like in the spectrum?) Ha Hb Range of Coupling Constant Ha Hb Structure H 11-18 Hz H H H H 6-14 Hz 0-3 Hz H 93 Putting It Together: Spectroscopy Week 4 1. You identify a new compound X. Mass spectroscopy suggests a molecular formula of C9H12O, and the following IR and proton NMR spectra are recorded: Deduce the structure of compound X, and explain the assignment of all of the important features in both spectra above. (Hint: What information can you deduce from the molecular formula alone?) OH 94 Putting It Together: Spectroscopy Week 4 1. You have just synthesized a new compound, and the following spectroscopic data is obtained: From the mass spectrum, you deduce that the molecular formula is C10H12O. The infrared spectrum is: wavenumbers (cm1): 3800 3400 3000 2600 2200 2000 1800 1600 1400 1200 1000 800 From the infrared spectrum, what functional groups are definitely present: From the infrared spectrum, what functional groups are definitely absent: C=O (probably C=C, but you didn't need to list this for credit...) OH The proton NMR spectrum is: 3H 5H 2H 2H Draw your best choice for the structure of this molecule in the box below: O CH3 95 Putting It Together: Spectroscopy Week 4 1. You have just synthesized a new compound, and the following spectroscopic data is obtained: From the mass spectrum, you deduce that the molecular formula is C4H8O. The infrared spectrum is: wavenumbers (cm1): 3800 3400 3000 2600 2200 2000 1800 1600 1400 1200 1000 800 From the infrared spectrum, what functional groups are definitely present: From the infrared spectrum, what functional groups are definitely absent: C=O C=C OH 3H The proton NMR spectrum is: 2H 1H 1H 1H Draw your best choice for the structure of this molecule in the box below: CH3 H C C H O C H2 H 96 Putting It Together: Spectroscopy Week 4 1. You have just synthesized a new compound, and the following spectroscopic data is obtained: From the mass spectrum, you deduce that the molecular formula is C5H9O2Br. The infrared spectrum is: wavenumbers (cm1): 3800 3400 3000 2600 2200 2000 1800 1600 1400 1200 1000 800 From the infrared spectrum, what functional groups are definitely present: From the infrared spectrum, what functional groups are definitely absent: C=O OH C=C The proton NMR spectrum is: 3H 3H 1H 2H TMS Draw your best choice for the structure of this molecule in the box below: O O Br ...
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This note was uploaded on 05/01/2008 for the course CHEM 51 taught by Professor Gribble during the Spring '08 term at Dartmouth.

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