Vitamins are a diverse group of organic compounds required in small amounts for normal metabolism. Vitamin A (retinol) is fat-soluble and essential for vision; Vitamin B6 (pyridoxine) is water-soluble and involved in amino acid metabolism; Vitamin C (ascorbic acid) is water-soluble and acts as an antioxidant. Properties vary widely among individual vitamins. They are not a single chemical entity and cannot be represented by one formula, structure, or set of physical constants. Comprehensive data must be retrieved per specific vitamin from sources such as PubChem.