{"knowledge_schema": {"broad_category": "Chemistry \u2192 Organic Chemistry \u2192 Reactions and Mechanisms", "refinement": "This problem involves identifying reagents for specific organic transformations, focusing on nucleophilic addition and hydrolysis reactions.", "specific_scope": "The transformations include the conversion of butan-2-one to a nitrile derivative and the subsequent hydrolysis of that derivative to a carboxylic acid.", "goal": "Determine the correct reagents (X and Y) that facilitate the specified organic transformations."}, "summary": "This problem requires knowledge of organic chemistry reactions, specifically the identification of appropriate reagents for transforming butan-2-one into 2-hydroxy-2-methylbutanenitrile and then converting that nitrile into 2-(4-benzylphenyl)-2-hydroxybutanoic acid. The correct reagents are X = NaHSO3 for the first transformation and Y = HCl for the hydrolysis, which aligns with the mechanisms of nucleophilic addition and acid-catalyzed hydrolysis."}