A ketohexose is a ketone

Ketone

In organic chemistry, a ketone is an organic compound with the structure RCR', where R and R' can be a variety of atoms and groups of atoms. It features a carbonyl group bonded to two other carbon atoms. Many ketones are known and many are of great importance in industry and in biology...

-containing hexose

Hexose

In organic chemistry, a hexose is a monosaccharide with six carbon atoms, having the chemical formula C6H12O6. Hexoses are classified by functional group, with aldohexoses having an aldehyde at position 1, and ketohexoses having a ketone at position 2....

 (a six-carbon monosaccharide

Monosaccharide

Monosaccharides are the most basic units of biologically important carbohydrates. They are the simplest form of sugar and are usually colorless, water-soluble, crystalline solids. Some monosaccharides have a sweet taste. Examples of monosaccharides include glucose , fructose , galactose, xylose...

). The most common ketohexoses, each of which represents a pair of enantiomer

Enantiomer

In chemistry, an enantiomer is one of two stereoisomers that are mirror images of each other that are non-superposable , much as one's left and right hands are the same except for opposite orientation. It can be clearly understood if you try to place your hands one over the other without...

s (D- and L-isomers), include fructose

Fructose

Fructose, or fruit sugar, is a simple monosaccharide found in many plants. It is one of the three dietary monosaccharides, along with glucose and galactose, that are absorbed directly into the bloodstream during digestion. Fructose was discovered by French chemist Augustin-Pierre Dubrunfaut in 1847...

, psicose

Psicose

D-Psicose is an ultralow-energy monosaccharide sugar. It is a C-3 epimer of D-fructose, and is present in small quantities in agricultural products and commercially-prepared carbohydrate complexes. It is known as a "rare sugar" because it is rarely found in nature, and even when found, only in...

, sorbose

Sorbose

Sorbose is a ketose belonging to the group of sugars known as monosaccharides. It has a sweetness that is equivalent to sucrose . The commercial production of vitamin C often begins with sorbose. L-Sorbose is the configuration of the naturally occurring sugar....

, and tagatose

Tagatose

Tagatose is a functional sweetener. It is a naturally occurring monosaccharide, specifically a hexose. It is often found in dairy products, and is very similar in texture to sucrose and is 92% as sweet, but with only 38% of the calories....

. Ketohexose is stable over a wide pH range, and with a primary pK_a of 10.28, will only deprotonate at high pH, so is marginally less stable than aldohexose

Aldohexose

An aldohexose is a hexose with an aldehyde group on one end.The aldohexoses have four chiral centres for a total of 16 possible aldohexose stereoisomers . Of these, only three commonly occur in nature: D-glucose, D-galactose, and D-mannose...

 in solution.

D-Fructose Fructose Fructose, or fruit sugar, is a simple monosaccharide found in many plants. It is one of the three dietary monosaccharides, along with glucose and galactose, that are absorbed directly into the bloodstream during digestion. Fructose was discovered by French chemist Augustin-Pierre Dubrunfaut in 1847...	D-Psicose Psicose D-Psicose is an ultralow-energy monosaccharide sugar. It is a C-3 epimer of D-fructose, and is present in small quantities in agricultural products and commercially-prepared carbohydrate complexes. It is known as a "rare sugar" because it is rarely found in nature, and even when found, only in...	D-Sorbose Sorbose Sorbose is a ketose belonging to the group of sugars known as monosaccharides. It has a sweetness that is equivalent to sucrose . The commercial production of vitamin C often begins with sorbose. L-Sorbose is the configuration of the naturally occurring sugar....	D-Tagatose Tagatose Tagatose is a functional sweetener. It is a naturally occurring monosaccharide, specifically a hexose. It is often found in dairy products, and is very similar in texture to sucrose and is 92% as sweet, but with only 38% of the calories....
L-Fructose	L-Psicose	L-Sorbose	L-Tagatose