Ch.8 - Reactions of Alkenes

Wade9th EditionOrganic ChemistryISBN: 9780135213728Not the one you use?Change textbook

Wade 9th Edition

Ch.8 - Reactions of Alkenes

Problem 29c,d

Chapter 8, Problem 29c,d

Predict the products, including stereochemistry where appropriate, for the m-chloroperoxybenzoic acid epoxidations of the following alkenes.
c. cis-cyclodecene
d. trans-cyclodecene

Verified step by step guidance

Identify the reagent and its function: m-Chloroperoxybenzoic acid (m-CPBA) is a peracid commonly used for epoxidation of alkenes. It reacts with the double bond of an alkene to form an epoxide (a three-membered cyclic ether). The reaction is stereospecific, meaning the stereochemistry of the starting alkene is retained in the product.

Analyze the structure of the starting material for part (c): cis-cyclodecene is a cyclic alkene with a cis configuration, meaning the substituents on the double bond are on the same side of the ring. This stereochemistry will influence the product.

Predict the product for part (c): The epoxidation of cis-cyclodecene with m-CPBA will result in a cis-epoxide. The oxygen atom from m-CPBA will add to the double bond, forming a three-membered ring with the same cis stereochemistry as the starting material.

Analyze the structure of the starting material for part (d): trans-cyclodecene is a cyclic alkene with a trans configuration, meaning the substituents on the double bond are on opposite sides of the ring. This stereochemistry will also be retained in the product.

Predict the product for part (d): The epoxidation of trans-cyclodecene with m-CPBA will result in a trans-epoxide. The oxygen atom from m-CPBA will add to the double bond, forming a three-membered ring with the same trans stereochemistry as the starting material.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Epoxidation

Epoxidation is a chemical reaction that converts alkenes into epoxides, which are three-membered cyclic ethers. This reaction typically involves the use of peracids, such as m-chloroperoxybenzoic acid (m-CPBA), which adds an oxygen atom across the double bond of the alkene. The stereochemistry of the epoxide product is influenced by the configuration of the starting alkene, making it essential to consider whether the alkene is cis or trans.

Stereochemistry

Stereochemistry refers to the study of the spatial arrangement of atoms in molecules and how this affects their chemical behavior. In the context of epoxidation, the stereochemical outcome is crucial, as the formation of the epoxide can lead to different products depending on whether the starting alkene is in a cis or trans configuration. Understanding stereochemistry helps predict the orientation of substituents in the resulting epoxide, which can influence reactivity and interactions with other molecules.

Cycloalkenes

Cycloalkenes are cyclic hydrocarbons that contain at least one carbon-carbon double bond. In the case of cis- and trans-cyclodecene, the difference in the arrangement of hydrogen atoms around the double bond affects the reactivity and the stereochemical outcome of reactions such as epoxidation. Recognizing the structural differences between these isomers is vital for predicting the products of their reactions, including the stereochemical implications of the epoxide formation.

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Related Practice

Textbook Question

Magnesium monoperoxyphthalate (MMPP) epoxidizes alkenes much like mCPBA. MMPP is more stable, however, and it may be safer to use for large-scale and industrial reactions. Propose a mechanism for the reaction of trans-2-methylhept-3-ene with MMPP, and predict the structure of the product(s).

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Textbook Question

a. Propose a mechanism for the conversion of cis-hex-3-ene to the epoxide (3,4-epoxyhexane) and the ring-opening reaction to give the glycol, hexane-3,4-diol. In your mechanism, pay particular attention to the stereochemistry of the intermediates and products.

b. Repeat part (a) for trans-hex-3-ene. Compare the products obtained from cis- and trans-hex-3-ene. Is this reaction sequence stereospecific?

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Textbook Question

Show how you would accomplish each of the following synthetic conversions.

(b)

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Textbook Question

Predict the products, including stereochemistry where appropriate, for the m-chloroperoxybenzoic acid epoxidations of the following alkenes.

a. cis-hex-2-ene

b. trans-hex-2-ene