Ascorbic Acid is a naturally occurring organic compound with antioxidant properties. It is a white solid but impure samples can appear yellowish. It dissolves well in water to give mildly acidic solutions. Ascorbic acid is one form ("vitamer") of Vitamin C. The name is derived from a- (meaning "no") and scorbutus (scurvy), the disease caused by a deficiency of vitamin C. Being derived from glucose, many animals are able to produce it, but humans require it as part of their nutrition.
Ascorbic acid resembles the sugar from which it is derived, being a ring containing many oxygen functional groups. The molecule exists in equilibrium with two ketone tautomers, which are less stable than the enol form. These forms rapidly interconvert in solutions of ascorbic acid.