{"knowledge_schema": {"broad_category": "Chemistry \u2192 Organic Chemistry \u2192 Reaction Mechanisms", "refinement": "This problem involves identifying starting materials for specific organic reactions that yield diketones through the use of reagents like hydrochloric acid and sodium nitrite.", "specific_scope": "The focus is on determining the correct starting compounds that, when treated with the specified reagents, will produce the diketones 3-ethyl-2,4-pentanedione and 2,5-dimethyl-3-hexanone.", "goal": "Identify the correct starting materials C and D from the given candidates that will yield the specified diketones upon reaction."}, "summary": "This problem is rooted in organic chemistry, specifically in understanding reaction mechanisms that lead to the formation of diketones. The task is to identify the appropriate starting materials for two separate reactions that yield specific diketones when treated with hydrochloric acid and sodium nitrite. The goal is to match the correct starting compounds from the provided options to the resulting diketones, ensuring that the structures align with the expected products. The correct answer is C = 3-ethyl-2-pentanone and D = 2,5-dimethyl-3-hexan-2-one."}