Ascorbic acid, also known as Vitamin C, is a water-soluble essential nutrient with potent antioxidant properties. It plays critical roles in collagen biosynthesis, carnitine and neurotransmitter synthesis, and immune function. Chemically, it is a six-carbon lactone that readily undergoes reversible oxidation to dehydroascorbic acid. Found naturally in citrus fruits, berries, and vegetables, it is widely used as a food additive (E300) for its preservative and nutritional benefits. It is stable in dry form but degrades in solution when exposed to heat, light, or oxygen. Its pKa values are 4.17 and 11.57, making it acidic in aqueous solutions.