Hexose

Hexoses are monosaccharides whose carbon skeleton includes six carbon atoms. They all have the molecular formula C6H12O6 and differ by the type of carbonyl functional group. If it is a keto group, it is called ketohexoses with an aldehyde group they are called aldohexoses. The remaining carbon atoms in the structure having hydroxy groups. The best-known representatives of the hexoses are glucose ( a aldohexose ) and fructose ( a ketohexose ). Furthermore, D -galactose and D-mannose in nature are very important industrially, the L- sorbose is for vitamin C synthesis of interest. In the scheme of carbohydrates aldohexoses and ketohexoses in turn are sub-groups of aldoses or ketoses of.

• 2.1 All ketohexoses in Fischer projection

Aldohexoses

The aldohexoses having four chiral centers, there are therefore 16 stereoisomers. In nature, only D -glucose, D -galactose and D-mannose are present in larger amounts. D- Talose occurs as part of the antibiotic effect and formed by Streptomyces Hygromycine. The D / L- configuration refers in aldohexoses always on the position of the OH group at C- 5 atom and has no relation to the rotational direction of the optical activity.

All aldohexoses in Fischer projection

Altrose

Glucose

Mannose

Gulose

Idose

Galactose

Talose

The names of the aldohexoses you can easily remember the following mnemonic: "All the old geese Would -be in the garden dancing " with the initials of saying words similar to those of aldohexoses (optionally also " cluck " instead of " geese ", then the likelihood of confusion on the lower with G starting sugars, "good" instead of "You're welcome " takes more relevant to gulose So. cluck like all the Old Well in the garden dancing).

Through an intramolecular hemiacetal formation, these open-chain molecules are in equilibrium with the six-membered pyranose - or five-membered furanose. The pyranoses have an oxygen bridge between the 1st and 5th, diebei the furanoses between 1 and 4 carbon atom. The oxygen atom of the aldehyde group to a hydroxy group. This adds another layer chirality. The two resulting configurational called " anomers ", they are prefixed by α - or β - differentiated.

Ketohexoses

The ketohexoses have three chiral centers, therefore there are eight stereoisomers. D / L configuration also applies to the position of the OH group at the 5 carbon atom and has no influence on the direction of the optical activity. In nature, only the four D- isomers occur.

All ketohexoses in Fischer projection

Fructose

Sorbose

Tagatose