CH3OHPH DHH LoH HaC The Wittig Reaction: Ketones and aldehydes react with phosphorus ylides to form alkenes. Phosphorus ylides are prepared by an S,2 reaction between an alkyl halide and tripheny phosphine, followed by deprotonation by a strong base such as n-butyllithium. The mechanism of the Wittig reaction involves nucleophilic addition to give an intermediate betaine, which decomposes to give the alkene and tripheny phosphine oxide. The Wittig reaction works well to prepare mono di- and tri-substituted alkenes; tetra-substituted alkenes cannot be prepared by this method R=alkyl or h a phosphorus yhe R2C-P(ChS)3 betaine e6P’cHls 9(6H R2C-P(C6Hslo Oxidation Reduction of aldehydes and Ketones Preparation of Alcohols by Reduction of Aldehydes and Ketones: Reduction of simple aldehydes andThe Wittig Reaction: Ketones and aldehydes react with phosphorus ylides to form alkenes. Phosphorus ylides are prepared by an SN2 reaction between an alkyl halide and triphenylphosphine, followed by deprotonation by a strong base such as n-butyllithium. The mechanism of the Wittig reaction involves nucleophilic addition to give an intermediate betaine, which decomposes to give the alkene and triphenylphosphine oxide. The Wittig reaction works well to prepare mono￾di- and tri-substituted alkenes; tetra-substituted alkenes cannot be prepared by this method. Oxidation & Reduction of Aldehydes and Ketones Preparation of Alcohols by Reduction of Aldehydes and Ketones: Reduction of simple aldehydes and