Find the structure for the following molecules: Problem 1. 1
Problem 2. 2
Problem 3 3
Problem 4. 4
Problem 5. Examining the infrared spectrum of a compound allows us to: a. determine the types of functional groups present in the compound b. determine the carbon-­‐hydrogen framework of the compound c. determine the molecular weight of the compound d. determine the nature of the conjugated pi electron system in the compound ANSWER: A Problem 6. Cyclohexene and 2-­‐hexyne both have the molecular formula C6H10. How would you use infrared spectroscopy to distinguish between the two compounds? To use IR spectroscopy to distinguish between isomers, find a strong IR absorption present in one isomer
that is absent in the other isomer.
alkene peak at 3020-3100 cm 1
and at 1650-1670 cm 1
no alkene peaks
no alkyne peaks
alkyne peak of medium intensity
at 2100-2260 cm 1
−
−
−
Problem 7. Which of the following statements best describes the base peak in a mass spectrum? a. The peak from the most 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. ANSWER C Problem 8. What m/z fragments will be generated by alpha cleavage of the following molecule (phenylacetone):
This compound, phenylacetone, has the formula C9H10O and a nominal mass of 134. Alpha cleavage will
result in charged fragments at m/z = 43 and m/z = 119.
Problem 9. What is the structure of the C3H6Br2 if we know the following from 1H NMR spectrum: 2H quintet at 2.4 δ, J = 6 Hz
4H triplet at 3.5 δ, J = 6 Hz
ANS:
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BrCH2CH2CH2Br
Problem 10. What is the structure of the C7H14O if we know the following from 1H NMR spectrum: 6H triplet at 0.9 δ, J = 7 Hz
4H sextet at 1.6 δ, J = 7 Hz
4H triplet at 2.4 δ, J = 7 Hz
ANS:
Problem 11. What is the structure of the C8H9Br if we know the following from 1H NMR spectrum: 3H doublet at 2.0 δ, J = 7 Hz
1H quartet at 5.0 δ, J = 7 Hz
5H singlet at 7.3 δ
ANS:
Problem 12. What are the splitting pattern for the hydrogen atoms labeled a and b in 3-methyl-2-butanone (below)?
How many non-equivalent carbons are in this molecule (in other words, how many peaks in the 13C
NMR spectrum)?
ANSWER: a. SINGLET 3H ; b. 6H Doublet (split by the H of the 3rd Carbon) .
Problem 13. Which of the following compounds would show the longest wavelength λmax in its UV spectrum?
a.
b.
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c.
d.
ANSWER : c Problem 14. Consider the Diels-­‐Alder product below. Draw structures for the molecules A and B that generate this product indicating the diene and the dienophile. A= DIENE; B=DIENOPHILE Problem 15. Which of the following compounds will react as a diene in a Diels-Alder reaction? What is the name of
the orientation needed for reaction? ANSWER C
a.
b.
c.
d.
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