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Concept explainers
Interpretation:
The transition states of exo and endo Diels Ander reactions of maleic anhydride with cyclopentadiene are to be drawn. Also, the transition state that leads to only one enantiomer need to be shown in each.
Concept introduction:
A Diels Ander 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 Ander 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 a Diels Ander reaction because it has a lower energy.
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Chapter 13 Solutions
ORGANIC CHEM. VOL.1+2-W/WILEYPLUS
- Practice Problem 13.36b Problem 13.34 outlines a general method for the preparation of cis- or trans-disubstituted epoxides. Using that method, identify what reagents you would use to prepare the following epoxide from acetylene: H" 'Et The transformation above can be performed with some reagent or combination of the reagents listed below. Give the necessary reagent(s) in the correct order, as a string of letters (without spaces or punctuation, such as "EBF"). If there is more than one correct solution, provide just one answer. A B C D DMP or PCC На, Pt EtBr PHCH2BR E F H H2SO4, H20, HgSO4 МСРВА (RCO3зН) Na, NH3 (/) H2, Lindlar's cat. I K TSCI, py PhBr NANH2 1) EtMgBr; 2) H30+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_forwardThe diene lactone shown in part (a) has one electron-donating group (¬OR) and one electron-withdrawing group(C“O). This diene lactone is sufficiently electron-rich to serve as the diene in a Diels–Alder reaction.(a) What product would you expect to form when this diene reacts with methyl acetylenecarboxylate, a strong dienophile?arrow_forward
- (a) Draw a Kekulé structure that shows how the reactive positions of anthracene are the ends of a diene, appropriate for a Diels–Alder reaction.(b) The Diels–Alder reaction of anthracene with maleic anhydride is a common organic lab experiment. Predict the product of this Diels–Alder reaction.arrow_forwardOne step in the synthesis of dodecahedrane (Section 4.11) 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_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
- -Ocimene is a pleasant-smelling hydrocarbon found in the leaves of certain herbs. It has the molecular formula C10H16 and a UV absorption maximum at 232 nm. On hydrogenation with a palladium catalyst, 2,6-dimethyloctane is obtained. Ozonolysis of -ocimene, followed by treatment with zinc and acetic acid, produces the following four fragments: (a) How many double bonds does -ocimene have? (b) Is -ocimene conjugated or nonconjugated? (c) Propose a structure for -ocimene. (d) Write the reactions, showing starting material and products.arrow_forward2) The Diels-Alder reaction, developed by German chemists Otto Diels and Kurt Alder (who received the Nobel Prize in 1950 for their discovery), has great synthetic importance due to the possibility of forming an unsaturated six-membered cycle without involving intermediates ionic. About the reaction, answer: (a) Indicate the reagents necessary for the synthesis of the following compounds, indicating who is the diene and who is the dienophile.arrow_forward8. (a) Benzene derivatives exhibit medium to strong absorption in UV-region. Explain why aniline and phenoxide ion have strong UV-absorptions.arrow_forward
- A key step in the synthesis of naproxen, an NSAID more commonly known by its brand name, Aleve (Section 3.9), is a coupling reaction of 2-bromo6-methoxynaphthalene to form 2-methoxy-6-vinylnaphthalene. Show three different coupling reactions, and the required reagents, that could be used to carry out this step.arrow_forwardHydrocarbon 10 and ester 12 react upon heating to give a cycloaddition product D. (i) Suggest a structure for product D and provide a curved arrow mechanism that accounts for its formation. (ii) Draw the molecular orbitals corresponding to the HOMO of 10 and the LUMO of 12 and show that these are of suitable symmetry for a concerted cycloaddition to take place. (iii) Use frontier molecular orbital theory to account for the observation that the formation of D is faster in the presence of AlCl3. please answer all thank youarrow_forwardGive the structure of the major diastereoisomer formed in the two reactions below. Explain the stereochemical outcome with the aid of Newman projections/transition state diagrams.arrow_forward
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