{"knowledge_schema": {"broad_category": "Chemistry \u2192 Organic Reactions \u2192 Carbon-Carbon Bond Formation", "refinement": "This category includes reactions that form carbon-carbon double bonds through various mechanisms.", "specific_scope": "The Wittig reaction specifically involves the reaction of aldehydes or ketones with phosphonium ylides to form alkenes.", "goal": "Identify the correct reaction that exemplifies the Wittig reaction among the given options."}, "summary": "The Wittig reaction is a specific organic reaction that involves the formation of alkenes from aldehydes or ketones and phosphonium ylides. Among the provided options, the correct example of the Wittig reaction is 'Aldehyde + Phosphonium ylide \u2014> Alkene.' This highlights the unique mechanism of the Wittig reaction in creating carbon-carbon double bonds."}