Concept explainers
Answer the following questions about
a. What starting materials are needed to form
b. What starting materials are needed to form
c. What product is f ormed when
d. Draw the Robinson annulation product(s) formed by reaction of
e. Draw the structure of the most stable enol tautomer(s).
(a)
Interpretation: The starting materials needed to form
Concept introduction: In crossed Claisen condensation reaction, a base abstracts an acidic proton from an
Answer to Problem 24.65P
The starting materials needed to form
Figure 1
Explanation of Solution
The given compound is,
Figure 2
The starting materials needed to form
Figure 1
The base abstracts the proton from
Figure 3
The starting materials needed to form
(b)
Interpretation: The starting materials needed to form
Concept introduction: In crossed Claisen condensation reaction, a base abstracts an acidic proton from an
Answer to Problem 24.65P
The starting materials needed to form
Figure 4
Explanation of Solution
The given compound is,
Figure 2
The starting materials needed to form
Figure 4
The base abstracts the proton from
Figure 5
The starting materials needed to form
(c)
Interpretation: The product formed on treatment of
Concept introduction: Alkylation of carbonyl compounds takes place in the presence of a strong base. The use of appropriate base, solvent and temperature can yield one major product regioselectively. The first step is abstraction of proton and second step is attack of electrophile to form alkylated product.
Answer to Problem 24.65P
The product formed on treatment of
Figure 6
Explanation of Solution
The product formed on treatment of
Figure 7
The base
The product formed on treatment of
(d)
Interpretation: The products formed on Robinson annulations of
Concept introduction: Robinson annulation is a combination of Michael addition and intramolecular aldol condensation reactions. It takes place between
Answer to Problem 24.65P
The products formed on Robinson annulations of
Figure 8
Explanation of Solution
The first step is the Michael addition between
Figure 9
The base abstracts the proton between the two carbonyl groups to form enolate. The enolate formed gives the conjugate addition on methyl vinyl ketone followed by protonation resulting in
Figure 10
The base abstracts the acidic proton from the
The products formed on Robinson annulations of
(e)
Interpretation: The structure of the most stable enol form tautomer is to be drawn.
Concept introduction: Keto and enol form of a compound exists in the chemical equilibrium with each other. Enol form refers to the compound in which carbonyl group exist as hydroxyl group adjacent to carbon-carbon double bond.
Answer to Problem 24.65P
The structure of the most stable enol form tautomer is,
Figure 11
Explanation of Solution
The enol form tautomer of
Figure 12
The stability of enols depends on the stability of alkenes. The alkene with endo double bond is more stable in case of five membered ring.
Thus, the most stable enol form tautomer is,
Figure 11
The structure of the most stable enol form tautomer is shown in Figure 11.
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Chapter 24 Solutions
ORGANIC CHEM CONNECT ACCESS CARD
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- Organic Chemistry: A Guided InquiryChemistryISBN:9780618974122Author:Andrei StraumanisPublisher:Cengage Learning