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(chem212)[2009](s)quiz~750^_10044.pdf
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CHEM212 Quiz1 Key

1. The midportion of the infrared (IR) region used by organic chemists lies between _____________ and _____________. (wavenumber)
Answer: 400 cm-1 4000 cm-1 (page 406, 12.6)

2. What is the chemical shift value (ppm) of the compound with 1875 Hz in a 300M NMR spectrometer? ______
Answer: 6.25

3. Infrared spectroscopy identifies what ________________ are present.
Answer: functional groups

4. In a Mass spectrum, CH2Cl2 has some basic molecular peaks, what is the intensity ratio of them?
A. 3:1 B. 9:6:1 C. 3:2 D. 9:3:1 E. 6:3:1
Answer: B
Cl35Cl35 is 3*3=9
Cl35Cl37+Cl37Cl35=3*1+1*3=6
Cl37Cl37=1*1=1

5. Which one is the major mass of the charged fragments produced from the dehydration of cyclohexanol (hydroxycyclohexane)?


A. 81 B. 82 C. 83 D. 88 E. 80
Answer: B (homework 12.4)

6. Please draw the lines between each chemical and its major IR absorbance wavenumber (cm-1):

3500 strong; 1660 medium


1715 strong; 2240 medium

3030 weak; 1450~1600 medium
Answer:

1715 strong; 2240 medium


3500 strong; 1660 medium


3030 weak; 1450~1600 medium
(page 410 problem 12.5 modified)

7. For 13C, 14C, 16O, 32S, 19F, 31P, 1H, magnetic nuclei are ____________________
Answer: 13C 31P 19F 1H

8. Which has the higher energy, radiation with = 4.0 x 109 Hz or radiation with = 9.0 x 10-6 m?
Answer: = 9.0 x 10-6 m (homework 12.7)

9. Write as many molecular formulas as you can for M+ = 128 (molecular ion) in its mass spectra. Assume that the compound contains C and H and that O may or may not be present.
Answer: C9H20, C9H4O, C10H8, C8H16O, C7H12O2, C6H8O3, C5H4O4
(homework 12.1)

10. Where might the following compound have IR absorptions (cm-1)?


A. 1730, 2100, 3300 B. 1715, 2100, 3500
C. 1715, 1660, 3300 D. 1730, 1660, 3500
Answer: A
(homework 12.13 modified)