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Draw curved arrows to show the movement of electrons in this step of the mechanism. Arrow-pushing Instructions C↔XT Ph₂p-CHCH3 H3C :0: CH3 H3C :: PPh3 Et H -CH3 ча

Draw curved arrows to show the movement of electrons in this step of the mechanism. Arrow-pushing Instructions C↔XT Ph₂p-CHCH3 H3C :0: CH3 H3C :: PPh3 Et H -CH3 ча

Organic Chemistry
Organic Chemistry
8th Edition
ISBN:9781305580350
Author:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. Foote
Publisher:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. Foote
Chapter17: Carboxylic Acids
Section: Chapter Questions
Problem 17.44P
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CH3 Ph3P-CHCH3 H3C H3C Aldehydes and ketones are converted into alkenes by means of a direct nucleophilic addition called the Wittig reaction. In the reaction, a triphenylphosphorine ylide, also called a phosphorane, adds to an aldehyde/ketone to give a four-membered cyclic intermediate called an oxaphosphetane. The oxaphosphetane is not isolated but instead spontaneously decomposes to release triphenylphosphine oxide and an alkene. Ph3P-CHCH3 H3C The ylide is formed by reaction of triphenylphosphine, a good nucleophile, with a primary alkyl halide in an S 2 reaction, followed by deprotonation of the carbon with a strong base, such as butyllithium. The carbonyl carbon and the carbon originally bonded to the halogen become the two carbons with the double bond in the product alkene :0: CH3 Com The real value of the Wittig reaction lies in its ability to yield an alkene of predictable structure, as the C-C bond is precisely where the C=O bond was in the reactant and no isomers (other than E/Z isomers) are formed. Draw curved arrows to show the movement of electrons in this step of the mechanism. Arrow-pushing Instructions NOC XT CH3 H3C CH3 Et :: PPh3 H Ph3P=O -CH3 ча
Transcribed Image Text:CH3 Ph3P-CHCH3 H3C H3C Aldehydes and ketones are converted into alkenes by means of a direct nucleophilic addition called the Wittig reaction. In the reaction, a triphenylphosphorine ylide, also called a phosphorane, adds to an aldehyde/ketone to give a four-membered cyclic intermediate called an oxaphosphetane. The oxaphosphetane is not isolated but instead spontaneously decomposes to release triphenylphosphine oxide and an alkene. Ph3P-CHCH3 H3C The ylide is formed by reaction of triphenylphosphine, a good nucleophile, with a primary alkyl halide in an S 2 reaction, followed by deprotonation of the carbon with a strong base, such as butyllithium. The carbonyl carbon and the carbon originally bonded to the halogen become the two carbons with the double bond in the product alkene :0: CH3 Com The real value of the Wittig reaction lies in its ability to yield an alkene of predictable structure, as the C-C bond is precisely where the C=O bond was in the reactant and no isomers (other than E/Z isomers) are formed. Draw curved arrows to show the movement of electrons in this step of the mechanism. Arrow-pushing Instructions NOC XT CH3 H3C CH3 Et :: PPh3 H Ph3P=O -CH3 ча
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