chapter12

How could you use mass spectrometry to tell them

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Unformatted text preview: of molecular Ion is of no help, so must rely on fragmentation information M+ = 98 Fig. 12-6, p. 414 18 Practice Problem 12.4 Assume you have two unlabeled samples, on of methylcyclohexane and the other of ethylcyclopentane. How could you use mass spectrometry to tell them apart? B+ = 69 Loss of 29 F+ = 83 Loss of 15 M+ = 98 B+ = 83 Loss of 15 M+ = 98 Fig. 12-6, p. 414 19 Practice Problem 12.4 Assume you have two unlabeled samples, on of methylcyclohexane and the other of ethylcyclopentane. How could you use mass spectrometry to tell them apart? C2C3 HH B+ = 69 Loss of ethyl group F+ = 83 Loss methyl group M+ = 98 C3 H B+ = 83 Loss of methyl group M+ = 98 Fig. 12-6, p. 414 20 Problem 12.3 Two mass spectra C3 H are shown below. One spectrum C3C2C=C HHH C3C2C 2C =CC 3 H H H H HH corresponds to 2-methyl-2-pentene and C3 H the other to 2-hexene. Which is which? B+ = 41 F+ = 69 M+ = 84 B+ = 55 F+ = 69 M+ = 84 Fig. 12-7, p. 415 21 Problem 12.3 Two mass spectra C3 H are shown below. One spectrum corresponds to 2-methyl-2-pentene and C 3C 2C =C HHH the other to 2-hexene. Which is which? C3 H B+ = 41 F+ = 69 - mass 15 M+ = 84 C3C2C2C=CC3 H H H H HH Look at the structures above. Which fragments would be most stable; that is, where would you cleave the bond? Hint: Consider the stability of carbocations or radicals. B+ = 55 - mass 29 F+ = 69 - mass 15 M+ = 84 Fig. 12-7, p. 415 22 Problem 12...
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