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The Wittig reaction mechanism is a chemical process that involves the conversion of a carbonyl compound (aldehyde or ketone) into an alkene using a phosphorus ylide as the reagent. This reaction is named after its discoverer, German chemist Georg Wittig, and is widely used in organic synthesis to create carbon-carbon double bonds.
A ylide is a neutral molecule with a positive and negative charge on adjacent atoms, typically a phosphorus atom and a carbon atom. In the Wittig reaction, the ylide acts as the nucleophile and attacks the carbonyl carbon, leading to the formation of a new carbon-carbon double bond.
The base, usually a strong base such as potassium tert-butoxide, is used to deprotonate the phosphorus ylide, making it more nucleophilic and reactive towards the carbonyl compound. The base also helps to remove the proton from the newly formed alkene, making the reaction thermodynamically favored.
The main byproduct of the Wittig reaction is triphenylphosphine oxide, which is formed when the phosphorus ylide reacts with oxygen. Other minor byproducts may include phosphine sulfides and sulfones, depending on the reaction conditions and starting materials used.
The selectivity of the Wittig reaction can be influenced by several factors, including the reactivity of the carbonyl compound, the steric hindrance of the reactants, and the choice of the phosphorus ylide. The reaction conditions, such as temperature and solvent, can also affect the selectivity of the reaction.
