Ch.8 - Reactions of Alkenes

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

Wade 9th Edition

Ch.8 - Reactions of Alkenes

Problem 31

Chapter 8, Problem 31

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).

Verified step by step guidance

Step 1: Recognize that MMPP is a peracid, similar to mCPBA, and is used to epoxidize alkenes. The reaction involves the transfer of an oxygen atom from the peracid to the alkene, forming an epoxide.

Step 2: Analyze the structure of trans-2-methylhept-3-ene. It is an alkene with a double bond between carbons 3 and 4, and a methyl group attached to carbon 2. The trans configuration indicates that the substituents on the double bond are on opposite sides.

Step 3: Propose the mechanism for the reaction. The alkene undergoes electrophilic attack by the peracid (MMPP). The oxygen atom from the peracid is transferred to the double bond, forming a three-membered epoxide ring. This occurs via a concerted mechanism where the π-electrons of the alkene attack the electrophilic oxygen, and the peracid donates the oxygen atom.

Step 4: Predict the stereochemistry of the product. Since the starting alkene is trans, the epoxide ring will retain the stereochemical information. The substituents on the epoxide will be on opposite sides of the ring, consistent with the trans configuration.

Step 5: Draw the product structure. The product will be a trans-epoxide derived from trans-2-methylhept-3-ene. The methyl group on carbon 2 and the rest of the chain will remain unchanged, while the double bond is replaced by an epoxide ring.

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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 involves the conversion of alkenes into epoxides, which are three-membered cyclic ethers. This reaction typically occurs through the addition of an electrophilic oxygen species to the double bond of the alkene. In this case, magnesium monoperoxyphthalate (MMPP) acts as the oxidizing agent, facilitating the formation of the epoxide from trans-2-methylhept-3-ene.

Mechanism of Epoxidation

The mechanism of epoxidation generally involves the formation of a cyclic transition state where the alkene double bond attacks the electrophilic oxygen of the oxidizing agent. This results in the formation of a three-membered epoxide ring. Understanding this mechanism is crucial for predicting the stereochemistry and regioselectivity of the product formed from the reaction of trans-2-methylhept-3-ene with MMPP.

Stability of MMPP

Magnesium monoperoxyphthalate (MMPP) is noted for its stability compared to other peracids like mCPBA. This stability makes MMPP a safer choice for large-scale industrial applications. Its structure, which includes a magnesium ion and peroxy groups, contributes to its reactivity while minimizing the risks associated with handling more reactive peracids, thus making it a preferred reagent in organic synthesis.

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Related Practice

Textbook Question

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

c. cis-cyclodecene

d. trans-cyclodecene

Textbook Question

Predict the major products of the following reactions.

b. trans-hex-3-ene + peroxyacetic acid (CH₃CO₃H) in water

c. 1-methylcyclohexene + MMPP in ethanol

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Textbook Question

Predict the major products of the following reactions.

d. trans-cyclodecene + peroxyacetic acid in acidic water

e. cis-cyclodecene + mCPBA in CH₂Cl₂, then dilute aqueous acid

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

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

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Textbook Question

Predict the major products of the following reactions.

a. cis-hex-2-ene + mCPBA in chloroform

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