Concept explainers
Interpretation:
Among the given pair of compounds, the compound that has the greater enol content is to be identified.
Concept introduction:
Enol refers to an intermediate structure that consists of an
The percentage of enol in keto-enol tautomerism depends upon the stability of enol formed.
Answer to Problem 29P
Solution:
a) Among the given pair of compounds, the second compound has the greater enol content.
b) Among the given pair of compounds, the first compound has the greater enol content.
c) Among the given pair of compounds, the first compound has the greater enol content.
d) Among the given pair of compounds, the first compound has the greater enol content.
Explanation of Solution
a) The compound having higher enol content.
The given pair of compounds is shown below.
The formation of enol occurs when a molecule contains protons on its alpha carbon atom. The extraction of protons takes place from the alpha carbon atom of molecule to form an enol. In the given compounds, the first compound does not possess an alpha proton. Therefore, it does not form an enol. On the other hand, the second compound has alpha proton that can be extracted to form enol. Hence, the second compound has the greater enol content.
b) The compound having higher enol content.
The given pair of compounds is shown below.
The formation of enol occurs when a molecule contains protons on its alpha carbon atom. The extraction of protons takes place from the alpha carbon atom of molecule to form an enol. In the given compounds, the second compound does not possess an alpha proton. Therefore, it does not form an enol. On the other hand, the first compound has alpha proton that can be extracted to form enol. Hence, the first compound has the greater enol content.
c) The compound having higher enol content.
The given pair of compounds is shown below.
The formation of enol occurs when a molecule contains protons on its alpha carbon atom. The extraction of protons takes place from the alpha carbon atom of molecule to form an enol. Both the compounds have alpha protons. In this case, the position of the existing double bond in relation to the new double bond that results when the enol is generated is considered. Their enols are shown below.
The first compound forms a conjugated set of double bonds, whereas in the second compound, the two double bonds are completely isolated. The conjugation refers to a stabilizing characteristic. Therefore, the first compound has the greater enol content.
d) The compound having higher enol content.
The given pair of compounds is shown below.
The formation of enol occurs when a molecule contains protons on its alpha carbon atom. The extraction of protons takes place from the alpha carbon atom of molecule to form an enol. Both the compounds have alpha protons. In this case, the possible resonance forms of the enol are considered. Their enols with resonance forms are shown below.
The first compound contains two oxygen atoms. Both these oxygens carry the negative charge of the enolate that is the intermediate of the enol to keto tautomerization. Therefore, the first compound has the greater enol content.
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Chapter 21 Solutions
ORGANIC CHEMISTRY (LL)-W/SOLN.>CUSTOM<
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Organic ChemistryChemistryISBN:9781305580350Author:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. FootePublisher:Cengage Learning