Concept explainers
Interpretation:
Theproducts formed from Diels Alder reaction of (2Z,4Z)-hexa-2,4-diene with methyl propenoate are to be determined.
Concept introduction:
A Diels Alder reaction is one between a conjugate diene and a reactant containing a double bond (dienophile) to form a product. The product is called adduct.
Diels Alder reactions are highly stereospecific. The configuration of the dienophile is retained in the product and the reaction is a syn addition reaction.
The dienes react with dienophiles in cis forms rather than trans forms.
Endo and exo refer to the orientation of the dienophile and its electron-withdrawing group when it reacts with a diene in a Diels Ander reaction.
Endo is favored in the transition state of aDiels Ander reaction because it has a lower energy.
Want to see the full answer?
Check out a sample textbook solutionChapter 13 Solutions
Organic Chemistry
- Cyclooctatetraene (8-annulene) is non-aromatic because all four pi bonds are not found in the same plane in its lowest energy conformation. If this compound is reduced by two electrons to generate the dianion, it exhibits aromatic characteristics. Draw the pi MO diagram for these compounds if they are planar, and fill in the electrons. Based on that picture explain the difference in their aromaticity.arrow_forwardMany variations of ring-closing metathesis have now been reported. Tandem ring–opening–ring-closing metathesis can occur with cyclic alkenes that contain two additional carbon–carbon double bonds. In this reaction, the cycloalkene is cleaved, and two new rings are formed. [1] What compounds are formed in this tandem reaction with the following substrates? [2] Devise a synthesis of the substrate in part (b) that uses a Diels–Alder reaction with diethyl maleate as the dienophile.arrow_forwardUsing the Woodward–Hoffmann rules, predict the stereochemistry of belowreaction. a thermal [5,5] sigmatropic rearrangementarrow_forward
- a) What product is formed from the [1,7] sigmatropic rearrangement of a deuterium in the following triene? (b) Does this reaction proceed in a suprafacial or antarafacial manner under thermal conditions? (c) Does this reaction proceed in a suprafacial or antarafacial manner under photochemical conditions?arrow_forwardUsing one or more of the following compounds as starting materials or products illustrate, with an example, each of the following type of pericyclic reactions. Your answer should include curved arrow mechanisms. (i) a disrotatory thermal electrocyclic reaction (ii) a conrotatory photochemical electrocyclic reaction (iii) a [4+2] cycloaddition (iv) a [3,3]-sigmatropic rearrangementarrow_forward(a) Complete the following sequence of reactions (i.e., give the structure for compounds A and B), giving structural details of all key intermediates. heat & A COOCH3 H₁₂ Ni (b) Provide the bond line structures for the pair of compounds used for the Diels-Alder synthesis of the compound shown below. O B COOCH3 (c) Draw the two major products obtained when (3E,5Z)-2,2,3,6,7-pentamethylocta-3,5-diene reacts with HBr at low and high temperatures. Label the products as the kinetic or thermodynamic product AND, if applicable, use dashes and wedges to show the correct stereochemistry in the obtained products.arrow_forward
- A solution of 5-methylcyclopenta-1,3-diene rearranges at roomtemperature to a mixture containing 1-methyl-, 2-methyl-, and 5-methylcyclopenta-1,3-diene. (a) Show how both isomeric products areformed from the starting material by a sigmatropic rearrangementinvolving a C–H bond. (b) Explain why 2-methylcyclopenta-1,3-diene isnot formed directly from 5-methylcyclopenta-1,3-diene by a [1,3]rearrangement.arrow_forwardMany variations of ring-closing metathesis have now been reported. Tandem ring-opening-ring-closing metathesis can occur with cyclic alkenes that contain two additional carbon-carbon double bonds. In this reaction, the cycloalkene is cleaved, and two new rings are formed. [1] What compounds are formed in this tandem reaction with the following substrates? [2] Devise a synthesis of the substrate in part (b) that uses a Diels–Alder reaction with diethyl maleate as the dienophile.arrow_forwardOne step in the synthesis of dodecahedrane involves reaction of the tetraene C with dimethylacetylene dicarboxylate (D) to afford two compounds having molecular formula C16H16O4. This reaction has been called a domino Diels–Alder reaction. Identify the two products formed.arrow_forward
- 6. Answer ALL parts of this question: a) Draw all the molecular orbitals of ethene and buta-1,3-diene, indicating where applicable which are the HOMOS and which are the LUMOS in both the ground state and first excited state. b) Use relevant orbitals from those drawn above to explain why buta-1,3- diene reacts with ethene in a [4+2] cycloaddition reaction under thermal conditions, but if two molecules of ethene are to dimerise in a [2+2] cycloaddition reaction, then the reaction must be irradiated with ultraviolet light. c) Identify compound X in the following reaction (Scheme 4) and draw curly arrow mechanisms that lead to it and then lead from it to the final products. CO, Me .CO, Me heat heat CO,Me СО Ме Scheme 4 d) The reaction shown below (Scheme 5) is another example of a cycloaddition reaction. Identify the number of electrons involved in it, draw a curly arrow mechanism leading to the product and suggest whether this reaction would take place under thermal or photochemical…arrow_forward6. Answer ALL parts of this question: a) Draw all the molecular orbitals of ethene and buta-1,3-diene, indicating where applicable which are the HOMOS and which are the LUMOS in both the ground state and first excited state. b) Use relevant orbitals from those drawn above to explain why buta-1,3- diene reacts with ethene in a [4+2] cycloaddition reaction under thermal conditions, but if two molecules of ethene are to dimerise in a [2+2] cycloaddition reaction, then the reaction must be irradiated with ultraviolet light. c) Identify compound X in the following reaction (Scheme 4) and draw curly arrow mechanisms that lead to it and then lead from it to the final products. CO Me CO₂Me heat heat X CO₂Me CO Me Scheme 4 d) The reaction shown below (Scheme 5) is another example of a cycloaddition reaction. Identify the number of electrons involved in it, draw a curly arrow mechanism leading to the product and suggest whether this reaction would take place under thermal or photochemical…arrow_forward1-Chloro-1,2-diphenylethane can undergo E2 elimination to give either cis- or trans-1,2-diphenylethylene (stilbene). Draw Newman projections of the reactive conformations leading to both possible products, and suggest a reason why the trans alkene is the major product.arrow_forward
- Organic ChemistryChemistryISBN:9781305580350Author:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. FootePublisher:Cengage Learning