Dicarbonyl compounds such as quinones are reactive dienophiles.
(a)
(b)
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- The endiandric acids comprise a group of unsaturated carboxylic acids isolated from a tree that grows in the rainforests of eastern Australia. The methyl esters of endiandric acids D and E have been prepared from polyene Y by a series of two successive electrocyclic reactions: thermal ring closure of the conjugated tetraene followed by ring closure of the resulting conjugated triene. (a) Draw the structures (including stereochemistry) of the methyl esters of endiandric acids D and E. (b) The methyl ester of endiandric acid E undergoes an intramolecular [4 + 2] cycloaddition to form the methyl ester of endiandric acid A. Propose a possible structure for endiandric acid A.arrow_forwardCompound A, C9H₁6 reacts with 1 molar equivalent(s) of hydrogen upon catalytic hydrogenation. A undergoes reaction with ozone, followed by Zn treatment, to give: CHỊCHỊCH CH3CCH₂CH₂CH₂CH₂CH₂CCH3 || Propose a structure for A.arrow_forwardPure (S)-2-bromo-2-fluorobutane reacts with methoxide ion in methanol to give a mixture of (S)-2-fluoro-2-methoxybutane and three fluoroalkenes.(a) Use mechanisms to show which three fluoroalkenes are formedarrow_forward
- Reaction of HBr with 3-methylcyclohexene yields a mixture of four products: cis-and trans-1-bromo-3-methylcyclohexane and cis-and trans-1-bromo-2-methylcyclohexane. The analogous reaction of HBr with 3-bromocyclohexene yields trans-1, 2-dibromocyclohexane as the soleproduct. Draw structures of the possible intermediates, and then explain why only a single product is formed in this reaction.arrow_forwardCompounds A and B are isomers having molecular formula C5H12. Heating A with Cl2 gives a single product of monohalogenation, whereas heating B under the same conditions forms three constitutional isomers. What are thestructures of A and B?arrow_forwardCompound A, C₂H16 reacts with 1 molar equivalent(s) of hydrogen on catalytic hydrogenation. A undergoes reaction with ozone, followed by Zn treatment, to give: O CH3 O || CH3CCH₂CCH₂CCH3 CH3 Compound A Propose a structure for A. • You do not have to consider stereochemistry. • You do not have to explicitly draw H atoms. • In cases where there is more than one answer, just draw one.arrow_forward
- One 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_forwardWhen 2-iodo-1,4-dimethylcyclohexane is heated in acetic acid, CH3COOH, a mixture of substitution and elimination products is obtained. Provide structures for all possible products, writing [not drawing] the name of the mechanism by which each one is formed.arrow_forward(a) The Friedel-Crafts reaction of benzene with 2-chloro-3-methylbutane in the presence of AlCl3 occurs with a carbocation rearrangement. Give mechanistic explanation and the product formed. (b) Predict the product(s) will be formed from the following reactions: (i) Bromination of p-methylbenzoic acid (ii) Sulphonation of m-bromoanisole (iii) Friedel-craft acylation of o-bromonitrobenzenearrow_forward
- 1. At what position and on what ring would you expect the following substances to undergo electrophilic substitution? (b) CH3 Br lel CH3 2. Rank the compounds in each group according to their reactivity toward electrophilic substitution. (a) Chlorobenzene, o-dichlorobenzene, benzene (b) p-Bromonitrobenzene, nitrobenzene, phenol (c) Fluorobenzene, benzaldehyde, 0-xylene (d) Benzonitrile, p-methylbenzonitrile, p-methoxybenzonitrilearrow_forwardReaction of iodoethane with CN- yields a small amount of isonitrile, CH3CH2N≡C, along with the nitrile CH3CH2N≡N, as the major product. Write electron-dot structures for both products, assign formal charges as necessary, and propose mechanisms to account for their formation.arrow_forwardFor each alkane, which mono brominated derivatives could you form in good yield by free-radical bromination?(a) cyclopentane (b) methylcyclopentane(c) 2-methylpentane (d) 2,2,3,3-tetramethylbutanearrow_forward