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Information about 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.

Aldohexoses

The aldohexoses 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 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-OH HO-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 D-Altrose D-Glucose D-Mannose

CH=O CH=O CH=O CH=O | | | | HC-OH HO-CH HC-OH HO-CH | | | | HC-OH HC-OH HO-CH HO-CH | | | | HO-CH HO-CH HO-CH HO-CH | | | | HC-OH HC-OH HC-OH HC-OH | | | | CH2OH CH2OH CH2OH CH2OH D-Gulose D-Idose D-Galactose D-Talose

Of these D isomers all, except altrose, are naturally occurring. L-altrose has been isolated from strains of the bacterium Butyrivibrio fibrisolvens.[1]

A mnemonic (attributed to Louis Fieser) often employed to remember the eight aldohexoses is "all altruists gladly make gum in gallon tanks".

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: CH2OH CH2OH CH2OH CH2OH | | | | C=O C=O C=O C=O | | | | HC-OH HO-CH HC-OH HO-CH | | | | HC-OH HC-OH HO-CH HO-CH | | | | HC-OH HC-OH HC-OH HC-OH | | | | CH2OH CH2OH CH2OH CH2OH D-psicose D-fructose D-sorbose D-tagatose

Only the naturally occurring hexoses are capable of being fermented by yeasts.

Mutarotation

The aldehyde and ketone functional groups in these carbohydrates react with neighbouring hydroxyl functional groups to form intramolecular hemiacetals or hemiketals, respectively. The resulting ring structure is related to pyran, and is termed a pyranose. The ring spontaneously opens and closes, allowing rotation to occur about the bond between the carbonyl group and the neighbouring carbon atom, yielding two distinct configurations (α and β). This process is termed mutarotation. Hexose sugars can form dihexose sugars with a condensation reaction to form a 1,6-glycosidic bond.

Other Information

It is a weak acid and a weak electrolyte.

References

1. ^ US patent 4966845, "Microbial production of L-altrose", granted 1990-10-30, assigned to Government of the United States of America, Secretary of Agriculture 

See also

 •  • [ e]
Major families of biochemicals
Peptides | Amino acids | Nucleic acids | Carbohydrates | Lipids | Terpenes | Carotenoids | Tetrapyrroles | Enzyme cofactors | Steroids | Flavonoids | Alkaloids | Polyketides | Glycosides
Analogues of nucleic acids:Types of CarbohydratesAnalogues of nucleic acids:
General: Aldose | Ketose | Pyranose | Furanose
Geometry: Pentose | Hexose | Heptose | Cyclohexane conformation | Anomer | Mutarotation
Small/Large: Glyceraldehyde | Dihydroxyacetone | Erythrose | Threose | Erythrulose | Sedoheptulose
Pentoses: Arabinose | Deoxyribose | Lyxose | Ribose | Ribulose | Xylose | Xylulose
Hexoses: Glucose | Galactose | Mannose | Gulose | Idose | Talose | Allose | Altrose | Fructose | Sorbose | Tagatose | Psicose | Fucose | Rhamnose
Disaccharides: Sucrose | Lactose | Trehalose | Maltose
Polymers: Glycogen | Starch (Amylose | Amylopectin) | Cellulose | Chitin | Stachyose | Inulin | Dextrin
Glycosaminoglycans: Heparin | Chondroitin sulfate | Hyaluronan | Heparan sulfate | Dermatan sulfate | Keratan sulfate
Aminoglycosides: Kanamycin | Streptomycin | Tobramycin | Neomycin | Paromomycin | Apramycin | Gentamicin | Netilmicin | Amikacin
Organic chemistry is a specific discipline within chemistry which involves the scientific study of the structure, properties, composition, reactions, and preparation (by synthesis or by other means) of chemical compounds consisting primarily of carbon and hydrogen, which may
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Monosaccharides (from Greek : single, sacchar: sugar) are the simplest carbohydrates. They cannot be hydrolyzed into simpler sugars. They consist of one sugar and are usually colorless, water-soluble, crystalline solids. Some monosaccharides have a sweet taste.
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4, 2
(mildly acidic oxide)
Electronegativity 2.55 (Pauling scale)
Ionization energies
(more) 1st: 1086.5 kJmol−1
2nd: 2352.6 kJmol−1
3rd: 4620.5 kJmol−1

Atomic radius 70 pm
Atomic radius (calc.
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A chemical formula is a concise way of expressing information about the atoms that constitute a particular chemical compound. A chemical formula is also a short way of showing how a chemical reaction occurs.
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In organic chemistry, functional groups (or moieties) are specific groups of atoms within molecules, that are responsible for the characteristic chemical reactions of those molecules.
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aldehyde is an organic compound containing a terminal carbonyl group. This functional group, which consists of a carbon atom which is bonded to a hydrogen atom and double-bonded to an oxygen atom (chemical formula O=CH-), is called the aldehyde group.
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A ketone (pronounced as key tone) is either the functional group characterized by a carbonyl group (O=C) linked to two other carbon atoms or a chemical compound that contains this functional group.
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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 (24). Of these, only three commonly occur in nature: D -glucose, D -galactose, and D -mannose.
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A stereocenter, or stereogenic centre, is any atom in a molecule bearing groups such that an interchanging of any two groups leads to a stereoisomer [1]. In organic chemistry this usually refers to a carbon, phosphorus or sulfur atom, though it is also possible
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Stereoisomers are isomeric molecules whose atomic connectivity is the same but whose atomic arrangement in space is different.

Enantiomers

Main article: enantiomer

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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.
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Optical rotation or optical activity is the rotation of linearly polarized light as it travels through certain materials. It occurs in solutions of chiral molecules such as sucrose (sugar), solids with rotated crystal planes such as quartz, and spin-polarized gases of atoms
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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.

Allose is a C-3 epimer of glucose.
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Altrose is an aldohexose sugar. The D isomer is an unnatural monosaccharide. It is soluble in water and practically insoluble in methanol. L-altrose has been isolated from strains of the bacterium Butyrivibrio fibrisolvens.
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Glucose (Glc), a monosaccharide (or simple sugar), is an important carbohydrate in biology. The living cell uses it as a source of energy and metabolic intermediate.
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Mannose is a sugar monomer of the hexose series of carbohydrates.

Metabolism

Mannose enters the carbohydrate metabolism stream in two steps:
  • First it undergoes phosphorylation to mannose-6-phosphate by hexokinase.

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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. Both the D- and L-forms are not fermentable by yeast.

Gulose is a C-3 epimer of galactose.
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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. It is a component of dermatan sulfate and heparan sulfate, which are glycosaminoglycans.
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Galactose (Gal) (also called brain sugar[1]) is a type of sugar which is less sweet than glucose and not very water-soluble. It is considered a nutritive sweetener because it has food energy.

Galactan is a polymer of the sugar galactose.
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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.
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Altrose is an aldohexose sugar. The D isomer is an unnatural monosaccharide. It is soluble in water and practically insoluble in methanol. L-altrose has been isolated from strains of the bacterium Butyrivibrio fibrisolvens.
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Not to be confused with pneumonic.


A mnemonic (pronounced IPA: /niːˈmɒnɪk/ in RP, /nɨˈmɑnɨk/
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Louis F. Fieser (April 7, 1899 – July 25, 1977) 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.
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D-Psicose (D-ribo-2-hexulose, C6H12O6) 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.
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Fructose (or levulose) is a simple sugar (monosaccharide) found in many foods and is one of the three most important blood sugars along with glucose and galactose. Honey, tree fruits, berries, melons, and some root vegetables, such as beets, sweet potatoes, parsnips, and
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Sorbose is a ketose belonging to the group of sugars known as monosaccharides. The commercial production of vitamin C (ascorbic acid) often begins with sorbose. L-Sorbose is the configuration of the naturally-occurring sugar.
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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 (table sugar) and is 92% as sweet, but with only 38% of the calories.
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Ascomycota (sac fungi)
  • Saccharomycotina (true yeasts)
  • Taphrinomycotina
  • Schizosaccharomycetes (fission yeasts)
Basidiomycota (club fungi)
  • Urediniomycetes

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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.
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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.
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