Organic Chemistry

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10. Addition Reactions

Epoxidation

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This reaction adds a 3-membered cyclic ether (epoxide functional group) to an alkene using reagents called peroxy acids. These epoxides are highly strained, so they can react in very useful ring-opening reactions, which we will discuss later. 

Epoxides from Peroxy Acids

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General properties of epoxidation.

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Peroxy acids are compounds with the general molecular formula RCO3H. The most common examples are MCPBA and MMPP. These are essentially the same molecule, just with different –R groups. 

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The mechanism of how peroxy acids make epoxides.

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You typically won’t need to know this entire mechanism, but here is the first step:

General Reaction:

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Note: There should also be a partial bond drawn in where the double bond used to be on the cyclohexane. 

Epoxides from Halohydrins

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Halohydrins to epoxides via intramolecular SN2.

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Halohydrins can be deprotonated using a base to become a nucleophilic O-. Once this anion is created, it can participate in an intramolecular SN2 reaction with the halogen next to it, making a three-membered ring closure

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