Hexose

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Hexose

In organic chemistry

Organic chemistry

Organic chemistry is a discipline within chemistry which involves the science study of the structure, properties, composition, chemical reaction, and preparation of chemical compounds that contain carbon....
, a hexose is a monosaccharide

Monosaccharide

Monosaccharides are the most basic unit of carbohydrates. They are the simplest form of sugar and are usually colorless, water-soluble, crystal solids....
with six carbon

Carbon

Carbon is a chemical element with chemical symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalence?making four electrons available to form covalent bond chemical bonds....
atoms, having the chemical formula

Chemical formula

A chemical formula is a way of expressing information about the atoms that constitute a particular chemical compound, and how the relationship between those atoms changes in chemical reactions....
C₆H₁₂O₆. Hexoses are classified by functional group

Functional group

In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules....
, with aldohexoses having an aldehyde

Aldehyde

An aldehyde is an organic compound containing a terminal carbonyl group. This functional group, which consists of a carbon atom bonded to a hydrogen atom and double bond to an oxygen atom , is called the aldehyde group....
at position 1, and ketohexoses having a ketone

Ketone

In organic chemistry, a ketone is a type of organic compound which contains a carbonyl group bonded to two other carbon atoms in the form:Neither of the substituents R1 and R2 may be equal to hydrogen ....
at position 2.

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 ....
s have four chiral centres for a total of 16 possible aldohexose stereoisomers (2⁴). The D/L configuration is based on the orientation of the hydroxyl

Hydroxyl

Hydroxyl in chemistry stands for a molecule consisting of an oxygen atom and a hydrogen atom connected by a covalent bond. The neutral form is a hydroxyl Radical and the hydroxyl anion is called a hydroxide....
at position 5, and does not refer to the direction of optical activity. The eight D-aldohexoses are:

CH=O CH=O CH=O CH=O | | | | HC-OHHO-CH HC-OH HO-CH | | | | HC-OH HC-OH HO-CH HO-CH | | | | HC-OH HC-OH HC-OH HC-OH | | | | HC-OH HC-OH HC-OH HC-OH | | | | CH₂OH CH₂OH CH₂OH CH₂OH D-Allose

Allose

Allose is an aldohexose sugar. It is a rare monosaccharide that has been isolated from the leaves of the African shrub Protea rubropilosa. It is soluble in water and practically insoluble in methanol....
D-Altrose

Altrose

Altrose is an aldohexose sugar. D-Altrose is an unnatural monosaccharide. It is soluble in water and practically insoluble in methanol....
D-Glucose

Glucose

Glucose , a monosaccharide also known as grape sugar, blood sugar, or corn sugar, is a very important carbohydrate in biology....
D-Mannose

Mannose

Gulose

Gulose is an aldohexose sugar. It is an unnatural monosaccharide that exists as a syrup with a sweet taste. It is soluble in water and slightly soluble in methanol....
D-Idose

Idose

Idose is a hexose, a six carbon monosaccharide. It has an aldehyde group and is an aldose. It is not found in nature, but its uronic acid, iduronic acid, is important....
D-Galactose

Galactose

Galactose is a type of Carbohydrate which is less sweetness than glucose. It is considered a nutritive sweetener because it has food energy.Galactan is a polymer of the sugar galactose....
D-Talose

Talose

Talose is an aldohexose sugar. It is an unnatural monosaccharide that is soluble in water and slightly soluble in methanol. Some etymologists suggest that talose's name derives from the automaton of Greek mythology named Talos, but the relevance is unclear....

Of these D isomers, all except altrose

Altrose

Altrose is an aldohexose sugar. D-Altrose is an unnatural monosaccharide. It is soluble in water and practically insoluble in methanol....
are naturally occurring.

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Aldohexoses

The aldohexose

Aldohexose

Hydroxyl

Allose

Altrose

Altrose is an aldohexose sugar. D-Altrose is an unnatural monosaccharide. It is soluble in water and practically insoluble in methanol....
D-Glucose

Glucose

Glucose , a monosaccharide also known as grape sugar, blood sugar, or corn sugar, is a very important carbohydrate in biology....
D-Mannose

Mannose

Gulose

Gulose is an aldohexose sugar. It is an unnatural monosaccharide that exists as a syrup with a sweet taste. It is soluble in water and slightly soluble in methanol....
D-Idose

Idose

Idose is a hexose, a six carbon monosaccharide. It has an aldehyde group and is an aldose. It is not found in nature, but its uronic acid, iduronic acid, is important....
D-Galactose

Galactose

Talose

Altrose

Altrose is an aldohexose sugar. D-Altrose is an unnatural monosaccharide. It is soluble in water and practically insoluble in methanol....
are naturally occurring. L-altrose has been isolated from strains of the bacterium Butyrivibrio fibrisolvens.

A mnemonic

Mnemonic

A mnemonic device is a memory aid. Commonly met mnemonics are often verbal, something such as a very short poem or a special word used to help a person remember something, particularly lists, but may be visual, kinesthetic or auditory....
(attributed to Louis Fieser

Louis Fieser

Louis F. Fieser was an organic chemist, professor, and in 1968, professor emeritus at Harvard University. He was renowned as the inventor, in 1943, of a militarily effective form of napalm....
) often employed to remember the eight aldohexoses is "all altruists gladly make gum in gallon tanks".

Cyclic Hemiacetals

It has been known since 1926 that 6-carbon aldose sugars form cyclic hemiacetal

Hemiacetal

Hemiacetals and hemiketals are compounds of the general formula R1R'1COR2, where R2 is not hydrogen....
s. The diagram below shows the hemiacetal forms for D-glucose and D-mannose.

The numbered carbons in the open-chain forms correspond to the same numbered carbons in the hemiacetal forms. The formation of the hemiacetal causes carbon number 1, which is symmetric in the open-chain form, to become asymmetric in the cyclic version. This means that both glucose and mannose (as well as all the other aldohexoses) each have two cyclic forms. In solution, both of these exist in equilibrium with the open-chain form. The open-chain form, however, does not crystallize. Hence the two cyclic forms become separable when they are crystallized. For example, D-glucose forms an alpha crystal that has specific rotation

Specific rotation

The specific rotation of a chemical compound [a] is defined as the observed angle of optical rotation a when plane-polarized light is passed through a sample with a path length of 1 decimetre and a sample concentration of 1 gram per 1 millilitre....
of +112° and melting point of 146 °C, as well as a beta crystal that has specific rotation of +19° and melting point of 150 °C.

Ketohexoses

The ketohexoses have 3 chiral centres and therefore eight possible stereoisomers (2³). Of these, only the four D-isomers are known to occur naturally: CH₂OHCH₂OH CH₂OHCH₂OH | | | | C=O C=O C=O C=O | | | | HC-OH HO-CH HC-OH HO-CH | | | | HC-OHHC-OH HO-CHHO-CH | | | | HC-OHHC-OH HC-OHHC-OH | | | | CH₂OHCH₂OH CH₂OHCH₂OH 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....
D-fructose

Fructose

Fructose is a simple Reducing sugar sugar found in many foods and is one of the three important dietary monosaccharides along with glucose and galactose....
D-sorbose

Sorbose

Sorbose is a ketose belonging to the group of sugars known as monosaccharides. 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....

Only the naturally occurring hexoses are capable of being fermented by yeast

Yeast

Yeasts are eukaryote microorganisms classified in the Kingdom fungus, with about 1,500 species currently described; they dominate fungal diversity in the oceans....
s.

Mutarotation

The aldehyde and ketone functional groups in these carbohydrates react with neighbouring hydroxyl

Hydroxyl

Intramolecular

Intramolecular in chemistry describes a process or characteristic limited within the structure of a single molecule; a property or phenomenon limited to the extent of a single molecule....
hemiacetal

Hemiacetal

Hemiacetals and hemiketals are compounds of the general formula R1R'1COR2, where R2 is not hydrogen....
s and hemiketals, respectively. The resulting ring structure is related to pyran

Pyran

In chemistry, a pyran is a six membered heterocyclic ring consisting of five carbon atoms and one oxygen atom and containing two double bonds. The molecular formula is C5H6O....
, and is termed a pyranose

Pyranose

Pyranose is a collective term for carbohydrates which have a chemical structure that includes a six-membered ring consisting of five carbons and one oxygen....
. The ring spontaneously opens and closes, allowing rotation to occur about the bond between the carbonyl

Carbonyl

In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double bond to an oxygen atom : C=O.The term carbonyl can also refer to carbon monoxide as a ligand in an inorganic or organometallic complex ; in this situation, carbon is triple-bonded to oxygen : C=O....
group and the neighbouring carbon atom, yielding two distinct configurations (a and ß). This process is termed mutarotation

Mutarotation

'Mutarotation is the term given to the change in the specific rotation of a cyclic monosaccharide as it reaches an equilibrium between its α and β anomeric forms....
. Hexose sugars can form dihexose sugars with a condensation reaction to form a 1,6-glycosidic bond

Glycosidic bond

In chemistry, a glycosidic bond is a certain type of functional group that joins a carbohydrate molecule to another, which may be another carbohydrate....
.

Hexose

Aldohexoses

Cyclic Hemiacetals

Ketohexoses

Mutarotation

See also