Organic Chemistry
8th Edition
ISBN: 9781305580350
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
Heating D-altrose with dilute acid produces a nonreducing anhydro sugar (C6H1005). Methylation of the anhydro sugar followed by
acid hydrolysis yields 2,3,4-tri-O-methyl-D-altrose. The formation of the anhydro sugar takes place through a chair conformation of ẞ-
D-altropyranose in which the -CH2OH group is axial.
What is the structure of the anhydro sugar?
CH3
OH
HO
OH
I
H₂C
CH3
0.
0
H
H
H
H
HO
OH
OH
I
CH3
H₂C
H
H
H
H
CH₂
-OH
OH
HO
eTextbook and Media
Explain how is it formed.
The anhydro sugar is formed when the axial -CH2OH group reacts with C
to form a cyclic
SUPF
Because the anhydro sugar is
(i.e., an internal glycoside), it is a
sugar.
Methylation followed by acid hydrolysis converts the anhydro sugar to 2,3,4-tri-O-methyl-D-altrose.
When pure (S)-lactic acid is esterified by racemic butan-2-ol, the product is 2-butyl lactate, with the following structure:H+CH3 CH COOH CH3 CH CH3 CH CHOH OHCH2CH3 CH2CH3lactic acidC OOH CH O 3butan-2-ol 2-butyl lactate+(a) Draw three-dimensional structures of the two stereoisomers formed, specifying the configuration at each asymmetriccarbon atom. (Using your models may be helpful.)(b) Determine the relationship between the two stereoisomers you have drawn
Chapter 3 Solutions
Organic Chemistry
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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