Organic Chemistry, Loose-leaf Version
8th Edition
ISBN: 9781305865549
Author: William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. Foote
Publisher: Cengage Learning
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Chapter 3, Problem 3.24P
When oxaloacetic acid and acetyl-coenzyme A (acetyl-CoA) labeled with radioactive carbon-14 in position 2 are incubated with citrate synthase, an enzyme of the tricarboxylic acid cycle, only the following enantiomer of [2-l4C]citric acid is formed stereoselectively. Note that citric acid containing only 12C is achiral. Assign an R or S configuration to this enantiomer of [2-14C]citric acid. (Note: Carbon-14 has a higher priority than carbon-12.)
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When oxaloacetic acid and acetyl-coenzyme A (acetyl-CoA) labeled with radioactive
carbon-14 in position 2 are incubated with citrate synthase, an enzyme of the tricarboxylic
acid cycle, only the following enantiomer of [2-14C]citric acid is formed stereoselectively.
Note that citric acid containing only 12C is achiral. Assign an R or S configuration to this
enantiomer of [2-14C]citric acid. (Note: Carbon-14 has a higher priority than carbon-12.)
C-COOH
14CH,COOH
citrate
synthase
ČH,COOH + 14CH,CSCOA
НООС
-COH
CH,COOH
Oxaloacetic acid
Acetyl-CoA
[2-14C]Citric acid
The following bicyclic ketone has two a-carbons and three a-hydrogens. When this molecule
is treated with D,O in the presence of an acid catalyst, only two of the three a-hydrogens
exchange with deuterium. The a-hydrogen at the bridgehead does not exchange.
H
these two a-hydrogens exchange
H.
this a-hydrogen
does not exchange
H
How do you account for the fact that two a-hydrogens do exchange but the third
does not? You will find it helpful to build models of the enols by which exchange of
a-hydrogens occurs.
Threonine has two asymmetric centers and, therefore, has four stereoisomers. Naturally occurring l-threonine is (2S,3R)-threonine. Which of the following stereoisomers is l-threonine?
Chapter 3 Solutions
Organic Chemistry, Loose-leaf Version
Ch. 3.2 - Prob. 3.1PCh. 3.3 - Assign priorities to the groups in each set. (a)...Ch. 3.3 - Prob. 3.3PCh. 3.4 - Following are stereorepresentations for the four...Ch. 3.4 - Prob. 3.5PCh. 3.4 - Prob. 3.6PCh. 3.5 - How many stereoisomers exist for...Ch. 3.5 - How many stereoisomers exist for...Ch. 3.7 - Prob. 3.9PCh. 3.7 - Prob. 3.10P
Ch. 3.8 - If the side chain of the amino add is a methyl...Ch. 3.8 - Prob. BQCh. 3.8 - The amino acids cysteine and serine are shown....Ch. 3.8 - Prob. DQCh. 3.8 - As stated, proteins are stereochemically pure...Ch. 3.8 - As stated, proteins are stereochemically pure...Ch. 3 - Prob. 3.11PCh. 3 - One reason we can be sure that sp3-hybridized...Ch. 3 - Which compounds contain chiral centers? (a)...Ch. 3 - Prob. 3.15PCh. 3 - Prob. 3.16PCh. 3 - Prob. 3.17PCh. 3 - Mark each chiral center in the following molecules...Ch. 3 - Prob. 3.19PCh. 3 - Assign priorities to the groups in each set. (a) H...Ch. 3 - Following are structural formulas for the...Ch. 3 - Following is a staggered conformation for one of...Ch. 3 - Prob. 3.23PCh. 3 - When oxaloacetic acid and acetyl-coenzyme A...Ch. 3 - Prob. 3.25PCh. 3 - Mark each chiral center in the following molecules...Ch. 3 - Prob. 3.27PCh. 3 - Prob. 3.28PCh. 3 - Prob. 3.29PCh. 3 - Prob. 3.30PCh. 3 - Which of the following are meso compounds?Ch. 3 - Prob. 3.32PCh. 3 - Prob. 3.33PCh. 3 - Which of the following compounds are chiral?...Ch. 3 - Prob. 3.35PCh. 3 - Prob. 3.36PCh. 3 - Prob. 3.37PCh. 3 - The chiral catalyst (R)-BINAP-Ru is used to...Ch. 3 - Prob. 3.39P
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