CH Exam #4 (Take Home) Date Due: 11/25,26/2013

Transcription

1 CH Exam #4 (Take Home) Date Due: 11/25,26/2013 Section I - Multiple Choice - Choose the BEST answer from the choices given and place the letter of you choice in the space provided. 1. Energy absorbed by a molecule in the infrared spectrum corresponds to: A) the amount of energy needed to promote one electron from a bonding to an antibonding orbital B) the amount of energy needed to flip the spin of a hydrogen nucleus C) the energy needed to strip a molecule of one electron to generate a cation radical D) the amount of energy needed to increase bond stretching and bending 2. Choose the structure which best fits the IR spectrum shown below. A) B) C) D) O H O O O '00.~ ~ E5D! :tooo 20DO HAVENUMB ERI -.1 ctrum obtained from: SDBSWeb: 5DO 3. Which of the following statements best describes the base peak in a mass spectrum? A) The peak from the least stable radical B) The peak from the species that has the isotope with the highest atomic number C) The peak of highest intensity D) The peak from the molecule minus an electron 4. The mass spectrum at right is the spectrum of a compound which contains C,H,O, and one other atom. What is the other atom? A) N B) P C) Br D) Cl >, +-' '(i') a ' C Q) > ~ 0 Q) 40- Ct::: HS-NW-l SS9 M+ = 156 M+ = ,I II, ~ m/z 175

2 Following is the electron-impact mass spectrum of 2-methylbutane, 100 MS- I W >- +-' 'w ~ ' C Q) :>- += Q) Ct:: How would you describe the peak at m/z 72? A) the base peak B) the molecular ion peak C) the peak containing the heaviest isotopes D) the peak corresponding to the most stable fragment ion 6. How would you describe the peak at m/z 57? A) the peak corresponding to a butyl radical cation B) the molecular ion peak C) the peak corresponding to a propyl radical cation D) the peak corresponding to an isopentyl radical cation m/z Nuclear magnetic resonance spectroscopy primarily provides information about a molecule s: A) conjugated pi electron system. B) size and formula. C) carbon-hydrogen framework D) functional groups. 8. When looking at an NMR chart, the right-hand part if the chart is the: A) high-field, upfield side. B) low-field, downfield side. C) aromatic proton region. D) highly-deshielded proton region. 9. The exact place on the NMR chart where a nucleus absorbs is the: A) TMS peak. B) atom s spin quantum number. C) atom s chemical shift. D) atom s atomic number.

3 10. Describe the relationship between the indicated two protons: A) unrelated B) homotopic C) enantiotopic D) diastereotopic ifo H H:: I ~ ~ I 11. Describe the relationship between the indicated two protons: A) unrelated B) homotopic C) enantiotopic D) diastereotopic ~H H Ho.CH3 ' H CH3 12. Describe the relationship between the indicated two protons: A) unrelated B) homotopic C) enantiotopic D) diastereotopic ~H H~ Cl~ V Cl 13. How many types of magnetically non-equivalent protons are in the following molecule? A) 2 B) 3 C) 4 D) 5 ()OI I How many types of magnetically non-equivalent protons are in the following molecule? A) 2 B) 3 C) 4 D) 5 H3C \ CH2CH3 / C= / C \ H H 15. Which molecule with the formula C4H8Cl2 would give the following proton NMR spectrum? 145 A) B) yl Cl ~Cl I Cl C) D) Cl,... ~ ~ 'Cl ~ Cl H8P ppm

4 Spectral Analysis - Problem A

5 Spectral Analysis - Problem B

6 Spectral Analysis - Problem C

7 Spectral Analysis - Problem D Mass Spectral Data: Base peak at m/z = 43 No definitive molecular ion. Highest discernible peaks m/z = 84 (20% of base peak), m/z=85 (1.2% of base peak)

8 Spectral Analysis - Problem E - C8H14O3

9 Spectral Analysis - Problem F Mass Spectral Data: Molecular ion at m/z =107

10 Section II - Spectra Analysis - Instructions - Identify the compound described with the data supplied for the following six compounds. Partial credit will be given for a structural formula only. The bulk of the points, however, will be allocated to your use of the spectral and other data supplied. THEREFORE, YOU SHOULD CLEARLY STATE HOW YOU USED THE DATA SUPPLIED AND MAKE AN EFFORT TO ASSIGN ANY DIAGNOSTIC IR PEAKS, MASS SPEC PEAKS, OR NMR SIGNALS WHICH YOU USED TO ARRIVE AT YOUR FINAL STRUCTURE. You may answer on a separate sheet of paper. Please take the time to make your answers neat, organized, and concise. This does not have to be a term paper. (85 points)