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Aldonic Acid
An aldonic acid is any of a family of sugar acids obtained by oxidation of the aldehyde functional group of an aldose to form a carboxylic acid functional group. Thus, their general chemical formula is HOOC-(CHOH)n-CH2OH. Oxidation of the terminal hydroxyl group instead of the terminal aldehyde yields a uronic acid, while oxidation of both terminal ends yields an aldaric acid. Aldonic acids are typically prepared by oxidation of the sugar with bromine. They are generally found in their lactone form, with the ring structure essentially the same as in the original sugar's cyclic hemiacetal form, which is the form the sugar is usually found in. However, unlike hemiacetals, lactones do not have a chiral anomeric carbon, and they cannot form glycosidic linkages. Aldonic acids are found in many biological systems, and are the products of the oxidation of aldoses by Benedict's or Fehling's reagents. Their lactones are key intermediates in the Kiliani-Fischer synthesis of sugar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hemiacetal
A hemiacetal or a hemiketal has the general formula R1R2C(OH)OR, where R1 or R2 is hydrogen or an organic substituent. They generally result from the addition of an alcohol to an aldehyde or a ketone, although the latter are sometimes called hemiketals. Most sugars are hemiacetals. Nomenclature According to the IUPAC definition, in R1R2C(OH)OR R1 and R2 may or may not be a hydrogen. In a hemiketal, neither R-group can be a hydrogen. Hemiketals are regarded as hemiacetals where none of the R-groups are H, and are therefore a subclass of the hemiacetals. The Greek prefix ''hèmi'' means half, refers to the fact that a single alcohol has been added to the carbonyl group, in contrast to acetals or ketals, which are formed when a second alkoxy group has been added to the structure. Cyclic hemiacetals and hemiketals are sometimes called lactols.IUPAC Gold Boolactols/ref> They often form readily, especially when they are 5- and 6-membered rings. In this case an intramolecular OH group r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gluconic Acid
Gluconic acid is an organic compound with molecular formula C6H12O7 and condensed structural formula HOCH2(CHOH)4COOH. It is one of the 16 stereoisomers of 2,3,4,5,6-pentahydroxyhexanoic acid. In aqueous solution at neutral pH, gluconic acid forms the gluconate ion. The salts of gluconic acid are known as "gluconates". Gluconic acid, gluconate salts, and gluconate esters occur widely in nature because such species arise from the oxidation of glucose. Some drugs are injected in the form of gluconates. Chemical structure The chemical structure of gluconic acid consists of a six-carbon chain, with five hydroxyl groups positioned in the same way as in the open-chained form of glucose, terminating in a carboxylic acid group. In aqueous solution, gluconic acid exists in equilibrium with the cyclic ester glucono delta-lactone. Production Gluconic acid preparation was first reported by Hlasiwetz and Habermann in 1870 and involved the chemical oxidation of glucose. In 1880, Boutroux ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glucose
Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, using energy from sunlight, where it is used to make cellulose in cell walls, the most abundant carbohydrate in the world. In energy metabolism, glucose is the most important source of energy in all organisms. Glucose for metabolism is stored as a polymer, in plants mainly as starch and amylopectin, and in animals as glycogen. Glucose circulates in the blood of animals as blood sugar. The naturally occurring form of glucose is -glucose, while -glucose is produced synthetically in comparatively small amounts and is less biologically active. Glucose is a monosaccharide containing six carbon atoms and an aldehyde group, and is therefore an aldohexose. The glucose molecule can exist in an open-chain (acyclic) as well as ring (cyclic) form. Gluco ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fehling's Solution
In organic chemistry, Fehling's solution is a chemical reagent used to differentiate between water-soluble carbohydrate and ketone () functional groups, and as a test for reducing sugars and non-reducing sugars, supplementary to the Tollens' reagent test. The test was developed by German chemist Hermann von Fehling in 1849. Laboratory preparation Fehling's solution is prepared by combining two separate solutions: Fehling's A, which is a deep blue aqueous solution of copper(II) sulfate, and Fehling's B, which is a colorless solution of aqueous potassium sodium tartrate (also known as Rochelle salt) made strongly alkali with sodium hydroxide. These two solutions, stable separately, are combined when needed for the test because the copper(II) complex formed by their combination is not stable: it slowly decomposes into copper hydroxide in the alkaline conditions. The active reagent is a tartrate complex of Cu2+, which serves as an oxidizing agent. The tartrate serves as a ligand. Howe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Benedict's Reagent
Benedict's reagent (often called Benedict's qualitative solution or Benedict's solution) is a chemical reagent and complex mixture of sodium carbonate, sodium citrate, and copper(II) sulfate pentahydrate. It is often used in place of Fehling's solution to detect the presence of reducing sugars. The presence of other reducing substances also gives a positive result.Collins Edexcel International GCSEBiology, Student Book () p.42-43 Such tests that use this reagent are called the Benedict's tests. A positive test with Benedict's reagent is shown by a color change from clear blue to brick-red with a precipitate. Generally, Benedict's test detects the presence of aldehydes, alpha-hydroxy-ketones, and hemiacetals, including those that occur in certain ketoses. Thus, although the ketose fructose is not strictly a reducing sugar, it is an alpha-hydroxy-ketone and gives a positive test because the base in the reagent converts it into the aldoses glucose and mannose. Oxidation of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glycosidic
A glycosidic bond or glycosidic linkage is a type of covalent bond that joins a carbohydrate (sugar) molecule to another group, which may or may not be another carbohydrate. A glycosidic bond is formed between the hemiacetal or hemiketal group of a saccharide (or a molecule derived from a saccharide) and the hydroxyl group of some compound such as an alcohol. A substance containing a glycosidic bond is a glycoside. The term 'glycoside' is now extended to also cover compounds with bonds formed between hemiacetal (or hemiketal) groups of sugars and several chemical groups other than hydroxyls, such as -SR (thioglycosides), -SeR (selenoglycosides), -NR1R2 (N-glycosides), or even -CR1R2R3 (C-glycosides). Particularly in naturally occurring glycosides, the compound ROH from which the carbohydrate residue has been removed is often termed the aglycone, and the carbohydrate residue itself is sometimes referred to as the 'glycone'. S-, N-, C-, and O-glycosidic bonds Glycosidic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anomer
In carbohydrate chemistry, a pair of anomers () is a pair of near-identical stereoisomers that differ at only the anomeric carbon, the carbon that bears the aldehyde or ketone functional group in the sugar's open-chain form. However, in order for anomers to exist, the sugar must be in its cyclic form, since in open-chain form, the anomeric carbon is planar and thus achiral. More formally stated, then, an anomer is an epimer at the hemiacetal/hemiketal carbon in a cyclic saccharide. Anomerization is the process of conversion of one anomer to the other. As is typical for stereoisomeric compounds, different anomers have different physical properties, melting points and specific rotations. Nomenclature Two anomers are designated alpha (α) or beta (β), according to the configurational relationship between the ''anomeric centre'' and the ''anomeric reference atom'', hence they are relative stereodescriptors. The anomeric centre in hemiacetals is the anomeric carbon C-1; in hemi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chirality (chemistry)
In chemistry, a molecule or ion is called chiral () if it cannot be superposed on its mirror image by any combination of rotation (geometry), rotations, translation (geometry), translations, and some Conformational isomerism, conformational changes. This geometric property is called chirality (). The terms are derived from Ancient Greek χείρ (''cheir'') 'hand'; which is the canonical example of an object with this property. A chiral molecule or ion exists in two stereoisomers that are mirror images of each other, called enantiomers; they are often distinguished as either "right-handed" or "left-handed" by their absolute configuration or some other criterion. The two enantiomers have the same chemical properties, except when reacting with other chiral compounds. They also have the same physics, physical properties, except that they often have opposite optical activity, optical activities. A homogeneous mixture of the two enantiomers in equal parts is said to be racemic mixtu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclic Compound
A cyclic compound (or ring compound) is a term for a compound in the field of chemistry in which one or more series of atoms in the compound is connected to form a ring. Rings may vary in size from three to many atoms, and include examples where all the atoms are carbon (i.e., are carbocycles), none of the atoms are carbon (inorganic cyclic compounds), or where both carbon and non-carbon atoms are present (heterocyclic compounds). Depending on the ring size, the bond order of the individual links between ring atoms, and their arrangements within the rings, carbocyclic and heterocyclic compounds may be aromatic or non-aromatic; in the latter case, they may vary from being fully saturated to having varying numbers of multiple bonds between the ring atoms. Because of the tremendous diversity allowed, in combination, by the valences of common atoms and their ability to form rings, the number of possible cyclic structures, even of small size (e.g., < 17 total atoms) numbers in the many b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sugar Acid
A Sugar acid or acidic sugar is a monosaccharide with a carboxyl group at one end or both ends of its chain. Main classes of sugar acids include: * Aldonic acids, in which the aldehyde group (−CHO) located at the initial end ( position 1) of an aldose is oxidized. * Ulosonic acids, in which the −CH2(OH) group at the initial end of a 2-ketose is oxidized creating an α-ketoacid. * Uronic acids, in which the −CH2(OH) group at the terminal end of an aldose or ketose is oxidized. * Aldaric acids, in which both ends (−CHO and −CH2(OH)) of an aldose are oxidized. Examples Examples of sugar acids include: * Aldonic acids ** Glyceric acid (3C) ** Xylonic acid (5C) ** Gluconic acid (6C) ** Ascorbic acid (6C, unsaturated lactone) * Ulosonic acids ** Neuraminic acid (5-amino-3,5-dideoxy-D- ''glycero''-D- ''galacto''-non-2-ulosonic acid) ** Ketodeoxyoctulosonic acid (KDO or 3-deoxy-D- ''manno''-oct-2-ulosonic acid) * Uronic acids ** Glucuronic acid (6C) ** Galacturonic acid (6C) * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
