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Interpretation:
Given that 2-substituted-2-cyclopentenones are in a base catalyzed equilibrium with their 5-substituted-2-cyclopentenone isomers. Why such analogous isomerization is not observed for 2-substituted -2-cyclohexenones is to be explained.
Concept introduction:
The isomerization of cycloalkenones occurs through an enolate anion formed by the abstraction of acidic hydrogen by the base. Hydrogens on carbon α- to a carbonyl group and those on γ- carbon in a conjugated enone are acidic. If these hydrogens are removed, isomerization will occur. Otherwise isomerization is not possible.
To explain:
Why 2-substituted -2-cyclohexenones are not in a base catalyzed equilibrium with their 6-substituted -2-cyclohexenone isomers like 2-substituted-2-cyclopentenones.
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Chapter 22 Solutions
Organic Chemistry
- Nonconjugated , -unsaturated ketones, such as 3-cyclohexenone, are in an acid-catalyzed equilibrium with their conjugated , -unsaturated isomers. Propose a mechanism for this isomerization.arrow_forwardA solution of acetone [(CH3)2C=O] in ethanol (CH3CH2OH) in the presence of a trace of acid was allowed to stand for several days, and a new compound of molecular formula C7H16O2 was formed. The IR spectrum showed only one major peak in the functional group region around 3000 cm−1, and the 1H NMR spectrum is given here. What is the structure of the product?arrow_forwardPhenacetin is an analgesic compound having molecular formula C10H13NO2. Once a common component in over-thecounter pain relievers such as APC (aspirin, phenacetin, caffeine), phenacetin is no longer used because of its liver toxicity. Deduce the structure of phenacetin from its 1H NMR and IR spectra.arrow_forward
- An aromatic hydrocarbon with a molecular formula of C13H20 has an 1 H NMR spectrum with a signal at ~7 ppm that integrates to 5H. It also has two singlets; one of the singlets has 1.5 times the area of the second. What is the structure of the aromatic hydrocarbon?arrow_forwardThe following questions concern ethyl (2-oxocyclohexane)carboxylate.(a) Write a chemical equation showing how you could prepare ethyl (2-oxocyclohexane)-carboxylate by a Dieckmann cyclization.(b) Write a chemical equation showing how you could prepare ethyl (2-oxocyclohexane)-carboxylate by acylation of a ketone.(c) Write structural formulas for the two most stable enol forms of ethyl (2-oxocyclohexane)carboxylate.(d) Write the three most stable resonance contributors to the most stable enolate derived from ethyl (2-oxocyclohexane)carboxylate.(e) Show how you could use ethyl (2-oxocyclohexane)carboxylate to prepare 2-methylcyclohexanone.(f) Give the structure of the product formed on treatment of ethyl (2-oxocyclohexane)-carboxylate with acrolein (H2C=CHCH=O) in ethanol in the presence of sodium ethoxidearrow_forwardWhich of the following reactions will synthesize phenol from benzene? 1) HNO3 + H2SO4; 2) Fe, HCl; 3) NaNO2, HCl, 0-10 oC; 4) warm H2SO4 and H2O 1) HNO3 + H2SO4; 2) Fe, HCl; 3) NaNO2, HCl, 0-10 oC; 4) CuCN; 5) dilute acid and heat 1) Acetyl chloride & AlCl3; 2) bleach 1) Ph-N2+ + KI; 2) BrMgCH=CH2 in ether, followed by H3O+; 3) warm, conc'd KMnO4 1) Cl-CH(CH3)-CH2CH2CH3 + FeBr3; 2) hot, conc'd KMnO4arrow_forward
- Treatment of cis-4-bromocyclohexanol with HO− affords compound Aand cyclohex-3-en-1-ol. Treatment of trans-4-bromocyclohexanol under the same conditions forms compound B and cyclohex-3-en-1-ol. A and Bcontain different functional groups and are not isomers of each other.Propose structures for A and B and offer an explanation for theirformation.arrow_forwardCyclohexene can be converted to 1-cyclopentenecarbaldehyde by the following series of reactions. Propose a structural formula for each intermediate compound.arrow_forwardAldehydes and ketones react with thiols to yield thioacetals just as they react with alcohols to yield acetals. Predict the product of the following reaction, and propose a mechanism:arrow_forward
- The following substances can be prepared by a nucleophilic addition reaction between an aldehyde or ketoneand a nucleophile. Identify the reactants from which they were prepared. If the substance is an acetal, identifythe carbonyl compound and the alcohol; if it is an imine or enamine, identify the carbonyl compound and theamine. You do not have to consider stereochemistry. In cases where there is more than one answer, just giveone. Use Grignard reagents when an organometallic reagent is required. Draw the Grignard reagent as acovalent magnesium bromide.arrow_forwardAn aromatic hydrocarbon with a molecular formula of C13H20 has an 1H NMR spectrum with a signal at ~7 ppm that integrates to 5H. It also has two singlets; one of the singlets has 1.5 times the area of the second. What is the structure of the aromatic hydrocarbon?arrow_forwardAcid-catalyzed hydrolysis of the following epoxide gives a trans diol. CH3 CH3 CH3 НО, НО, H,SO, + H,O HO HO Only this glycol This glycol is is formed. not formed. Of the two possible trans diols, only one is formed. How do you account for this stereoselectivity?arrow_forward
- Introduction to General, Organic and BiochemistryChemistryISBN:9781285869759Author:Frederick A. Bettelheim, William H. Brown, Mary K. Campbell, Shawn O. Farrell, Omar TorresPublisher:Cengage LearningOrganic ChemistryChemistryISBN:9781305580350Author:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. FootePublisher:Cengage Learning
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