C6H12O6

C6H12O6 is the molecular formula that describes hexose sugars—six-carbon monosaccharides with twelve hydrogens and six oxygens. The term is commonly associated with glucose, fructose, and galactose, though many isomers exist. Hexoses can be classified as aldoses (aldohexoses) and ketoses (ketohexoses). The most familiar examples are the aldohexoses glucose and galactose, and the ketohexose fructose. The natural molecules exist predominantly in the D-configuration, which is important for biological recognition, and a number of stereoisomers exist (four chiral centers in the main chain yield 2^4 = 16 possible aldohexoses).

In aqueous solution hexoses interconvert between linear and cyclic forms. The cyclic forms include aldohexoses that can form a six-membered pyranose ring (glucose and galactose) and a five-membered furanose ring (fructose). Each ring can have α or β anomeric configurations, distinguished by the orientation of the anomeric hydroxyl group at the anomeric carbon. The open-chain form contains a aldehyde (glucose) or ketone (fructose) group, making them reducing sugars.

Molecular weight is about 180.16 g/mol. C6H12O6 is the building block for larger carbohydrates; units of glucose link to form starch and glycogen, while glucose is released during glycolysis and cellular respiration. Fructose is metabolized primarily in the liver, and galactose is converted to glucose-6-phosphate via the Leloir pathway. In foods, C6H12O6 is the principal component of many sugars and sweeteners and is involved in various biosynthetic pathways.