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Encyclopedia > Ascorbic acid
Ascorbic acid
IUPAC name (R)-3,4-dihydroxy-5-((S)- 1,2-dihydroxyethyl)furan-2(5H)-one
Identifiers
CAS number 50-81-7
Properties
Molecular formula C6H8O6
Molar mass 176.13 g/mol
Appearance White or light yellow solid
Density 1.65 g/cm³
Melting point

190 - 192 °C (dec) Image File history File links Download high-resolution version (1100x854, 45 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Ascorbic acid ... Image File history File links Size of this preview: 644 × 600 pixel Image in higher resolution (1100 × 1024 pixel, file size: 201 KB, MIME type: image/png) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Ascorbic acid Antioxidant... IUPAC nomenclature is a system of naming chemical compounds and of describing the science of chemistry in general. ... CAS registry numbers are unique numerical identifiers for chemical compounds, polymers, biological sequences, mixtures and alloys. ... A chemical formula is a concise way of expressing information about the atoms that constitute a particular chemical compound. ... This article does not cite any references or sources. ... For other uses, see Density (disambiguation). ... The melting point of a crystalline solid is the temperature range at which it changes state from solid to liquid. ...

Solubility in water Soluble
Acidity (pKa) 4.17 (first), 11.6 (second)
Hazards
MSDS ScienceLab.com
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references
This article deals with the molecular aspects of ascorbic acid. For information about its purpose in nutrition, see Vitamin C.

Ascorbic acid is an organic acid with antioxidant properties. Its appearance is white to light yellow crystals or powder. It is water soluble. The L-enantiomer of ascorbic acid is commonly known as vitamin C. The name is derived from the alpha privative a- (meaning no) and scorbuticus (scurvy), the disease caused by a deficiency of vitamin C. In 1937 the Nobel Prize for chemistry was awarded to Walter Haworth for his work in determining the structure of ascorbic acid (shared with Paul Karrer, who received his award for work on vitamins), and the prize for Physiology or Medicine that year went to Albert Szent-Györgyi for his studies of the biological functions of L-ascorbic acid. At the time of its discovery in the 1920s it was called hexuronic acid by some researchers.[1] Solubility is a chemical property referring to the ability for a given substance, the solute, to dissolve in a solvent. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... The acid dissociation constant (Ka), also known as the acidity constant or the acid-ionization constant, is a specific equilibrium constant for the reaction of an acid with its conjugate base in aqueous solution [1]. // When an acid dissolves in water, it partly dissociates forming hydronium ions and its conjugate... This page meets Wikipedias criteria for speedy deletion. ... In chemistry, the standard state of a material is its state at 1 bar (100 kilopascals) and 25 degrees Celsius (298. ... This article is about the nutrient. ... 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 contain any number of other elements, including nitrogen, oxygen, halogens as well... Space-filling model of the antioxidant metabolite glutathione. ... In chemistry, enantiomers (from the Greek ἐνάντιος, opposite, and μέρος, part or portion) are stereoisomers that are nonsuperimposable complete mirror images of each other, much as ones left and right hands are the same but opposite. ... This article is about the nutrient. ... The privative a (also known as privative alpha or α privativum) is the prefix a- expressing negation (e. ... Scurvy (N.Lat. ... Year 1937 (MCMXXXVII) was a common year starting on Friday (link will display the full calendar) of the Gregorian calendar. ... The Nobel Prizes (Swedish: ) are awarded for Physics, Chemistry, Literature, Peace, and Physiology or Medicine. ... Sir Walter Norman Haworth (born Chorley, Lancashire March 19, 1883 – March 19, 1950) was a British chemist who is best known for his groundbreaking work on ascorbic acid (vitamin C) whilst working at Birmingham University. ... Paul Karrer (April 21, 1889 – June 18, 1971) was a Swiss organic chemist best known for his work on vitamins. ... Albert Szent-Györgyi at the time of his appointment to the National Institutes of Health Albert Szent-Györgyi de Nagyrápolt (September 16, 1893 – October 22, 1986) was a Hungarian physiologist who won the Nobel Prize in Physiology or Medicine in 1937. ...

Contents

Chemistry

Acidity

Ascorbic acid behaves as a vinylogous carboxylic acid, where the double bond ("vinyl") transmits electron pairs between the hydroxyl and the carbonyl. There are two resonance structures for the deprotonated form, differing in the position of the double bond. Structure of a carboxylic acid The 3D structure of the carboxyl group A space-filling model of the carboxyl group Carboxylic acids are organic acids characterized by the presence of a carboxyl group, which has the formula -C(=O)OH, usually written -COOH or -CO2H. [1] Carboxylic acids are Bronsted... Resonance structures are diagrammatic tools in organic chemistry to symbolize resonant bonds between atoms in molecules. ...


Another way to look at ascorbic acid is to consider it as an enol. The deprotonated form is an enolate, which are usually strongly basic. However, the adjacent double bond stabilizes the deprotonated form. Enol (or, more officially, but less commonly: alkenol) is an alkene with hydroxyl group on one of the carbon atoms of the double bond. ... Enol (or, more officially, but less commonly: alkenol) is an alkene with hydroxyl group on one of the carbon atoms of the double bond. ...

Movement of electron pairs in deprotonation


Image File history File links Ascorbic_acidity3. ... Image File history File links Ascorbic_acidity3. ...

Tautomerism

Nucleophilic attack of ascorbic enol on proton to give 1,3-diketone
Nucleophilic attack of ascorbic enol on proton to give 1,3-diketone

Ascorbic acid also rapidly interconverts into two unstable diketone tautomers by proton transfer, although it is the most stable in the enol form. The proton of the enol is lost, and reacquired by electrons from the double bond, to produce a diketone. This is an enol reaction. There are two possible forms, 1,2-diketone and 1,3-diketone.
Image File history File links Ascorbic_diketone. ... In chemistry, a nucleophile (literally nucleus lover) is a reagent which is attracted to centres of positive charge. ... A diketone is a molecule containing two carbonyl groups. ... Tautomers are organic compounds that are interconvertible by a chemical reaction called tautomerization. ... In physics, the proton (Greek proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1. ... Enol (or, more officially, but less commonly: alkenol) is an alkene with hydroxyl group on one of the carbon atoms of the double bond. ...


Determination

The concentration of a solution of ascorbic acid can be determined in many ways, the most common ways involving titration with an oxidizing agent. Titration setup: the titrant drops from the burette into the analyte solution in the flask. ... European Union Chemical hazard symbol for oxidizing agents Dangerous goods label for oxidizing agents Oxidizing agent placard An oxidizing agent (also called an oxidant or oxidizer) is A chemical compound that readily transfers oxygen atoms or A substance that gains electrons in a redox chemical reaction. ...

DCPIP

A commonly used oxidising agent is the dye 2,6-dichlorophenol-indophenol, or DCPIP for short. The blue dye is run into the ascorbic acid solution until a faint pink colour persists for 15 seconds. DCPIP in its oxidised form DCPIP (2,6-dichlorophenol-indophenol) is a blue chemical compound used as a dye due to the fact that when it is in its oxidised state it is blue. ... Making a saline water solution by dissolving table salt (NaCl) in water This article is about chemical solutions. ...

Iodine

Another method involves using iodine and a starch indicator where iodine reacts with ascorbic acid and when all the ascorbic acid has reacted the iodine is then in excess, forming a blue-black complex with the starch indicator. This indicates the end point of the titration. Alternatively, ascorbic acid can be reacted with iodine in excess, followed by back titration with sodium thiosulfate while using starch as an indicator. For the record label, see Iodine Recordings. ... Starch (CAS# 9005-25-8) is a complex carbohydrate which is insoluble in water; it is used by plants as a way to store excess glucose. ... Indicator may mean: pH indicator, a chemical detector for protons in acid-base titrations Redox indicator, a chemical detector for redox titrations Complexometric indicator, a chemical detector for metal ions in complexometric titrations Dial indicator, an instrument that measures small distances Honeyguide, a genus of birds Turn signal of an...

Iodate and iodine

The above method involving iodine requires making up and standardising the iodine solution. One way round this is to generate the iodine in the presence of the ascorbic acid by the reaction of iodate and iodide ion in acid solution. An iodate is a salt of iodic acid. ... For other uses, see acid (disambiguation). ...

N-Bromosuccinimide

A much less common oxidising agent is N-bromosuccinimide, (NBS). In this titration the NBS oxidises the ascorbic acid (in the presence of potassium iodide and starch). When the NBS is in excess (i.e. the reaction is complete) the NBS liberates the iodine from the potassium iodide which then forms the blue/black complex with starch, indicating the end point of the titration. Flash point None R/S statement R: ? S: ? RTECS number  ? Supplementary data page Structure and properties n, εr, etc. ... Potassium iodide is a white crystalline salt with chemical formula KI, used in photography and radiation treatment. ...


Uses

Ascorbic acid is easily oxidized and so is used as a reductant in photographic developer solutions (among others) and as a preservative. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... A reducing agent (also called a reductant or reducer) is the element or a compound in a redox (reduction-oxidation) reaction (see electrochemistry) that reduces another species. ... This article is about the nutrient. ... // Dehydroascorbic acid (DHA) is an oxidized form of ascorbic acid. ... European Union Chemical hazard symbol for oxidizing agents Dangerous goods label for oxidizing agents Oxidizing agent placard An oxidizing agent (also called an oxidant or oxidizer) is A chemical compound that readily transfers oxygen atoms or A substance that gains electrons in a redox chemical reaction. ... This article is about the nutrient. ... This article does not cite any references or sources. ...


Exposure to oxygen, metals, light and heat destroy ascorbic acid, so it must be stored in dark and cold and not in a metal container.


The oxidized form of ascorbic acid is known as dehydroascorbic acid. // Dehydroascorbic acid (DHA) is an oxidized form of ascorbic acid. ...


The L-enantiomer of ascorbic acid is also known as vitamin C. The name "ascorbic" comes from its property of preventing and curing scurvy. Primates, including humans, and a few other species in all divisions of the animal kingdom, notably the guinea pig, have lost the ability to synthesize ascorbic acid and must obtain it in their food. Optical isomerism is a form of isomerism (specifically stereoisomerism) where the two different isomers are the same in every way except being non-superposable mirror images of each other. ... This article is about the nutrient. ... Scurvy (N.Lat. ... Families 15, See classification A primate is any member of the biological order Primates, the group that contains all the species commonly related to the lemurs, monkeys, and apes, with the latter category including humans. ... This article is about the species Cavia porcellus. ...


Ascorbic acid and its sodium, potassium, and calcium salts are commonly used as antioxidant food additives. These compounds are water soluble and thus cannot protect fats from oxidation: For this purpose, the fat-soluble esters of ascorbic acid with long-chain fatty acids (ascorbyl palmitate or ascorbyl stearate) can be used as food antioxidants. Eighty percent of the world's supply of ascorbic acid is produced in China. [2] For other meanings of the word salt see table salt or salt (disambiguation). ... Space-filling model of the antioxidant metabolite glutathione. ... Food additives are substances added to food to preserve flavor or improve its taste and appearance. ... Fats is the plural for fat, a generic term for a class of lipids in biochemistry. ... It has been suggested that this article or section be merged with Solution. ... A carboxylic acid ester. ... In chemistry, especially biochemistry, a fatty acid is a carboxylic acid often with a long unbranched aliphatic tail (chain), which is either saturated or unsaturated. ...


The relevant European food additive E numbers are: For the mathematical constant see: E (mathematical constant). ...

  1. E300 ascorbic acid,
  2. E301 sodium ascorbate,
  3. E302 calcium ascorbate,
  4. E303 potassium ascorbate,
  5. E304 fatty acid esters of ascorbic acid (i) ascorbyl palmitate (ii) ascorbyl stearate.

It can be added to water that has been treated with iodine to make it potable, neutralizing the unpleasant iodine taste. Ascorbic acid Mineral ascorbates are salts of ascorbic acid (vitamin C). ... Ascorbic acid Mineral ascorbates are salts of ascorbic acid (vitamin C). ... Ascorbic acid Mineral ascorbates are salts of ascorbic acid (vitamin C). ... Ascorbyl palmitate is an ester formed from ascorbic acid and palmitic acid. ... Ascorbyl stearate is an ester formed from ascorbic acid and stearic acid. ...


In plastic manufacturing ascorbic acid can be used to assemble molecular chains more quickly and with less waste than traditional synthesis methods.[3]


Antioxidant mechanism

Ascorbate acts as an antioxidant by being itself available for energetically favourable oxidation. Many oxidants (typically, reactive oxygen species) such as the hydroxyl radical (formed from hydrogen peroxide), contain an unpaired electron and thus are highly reactive and damaging to humans and plants at the molecular level. This is due to their interaction with nucleic acid, proteins and lipids. Reactive oxygen species oxidize (take electrons from) ascorbate first to monodehydroascorbate and then dehydroascorbate. The reactive oxygen species are reduced to water while the oxidized forms of ascorbate are relatively stable and unreactive, and do not cause cellular damage. Reactive oxygen species (ROS) include oxygen ions, free radicals and peroxides both inorganic and organic. ... R-phrases , , , , S-phrases , , , ,, , , , Flash point Non-flammable Related Compounds Related compounds Water Ozone Hydrazine Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references Hydrogen peroxide (H2O2) is a very pale blue liquid which appears colourless in... Look up nucleic acid in Wiktionary, the free dictionary. ...


Ascorbic acid synthesis in non-primates

Ascorbic acid is found in plants, animals, and single cell organisms.[4] All living animals either make it, eat it, or die from scurvy. Reptiles and older orders of birds make ascorbic acid in their kidneys. Recent orders of birds and most mammals make ascorbic acid in their livers where the enzyme L-gulonolactone oxidase is required to convert glucose to ascorbic acid.[5] Humans, guinea pigs, and some other primates are not able to make L-gulonolactone oxidase because of a genetic defect and are therefore unable to make ascorbic acid in their livers. This genetic mutation occurred about 63 million years ago [6] This would have had lethal consequences for the mutated primate were it not for the fact that it occurred to an arboreal animal living in a tropical environment where plenty of foodstuffs containing ascorbic acid were available throughout the year. Although ascorbic acid is a vital food nutrient for humans and is therefore termed a vitamin, it is a natural liver metabolite in most other animals. The effect of riboflavin deficiency on the activity of L-gulonolactone oxidase [L-gulono-gamma-lactone: oxygen 2-oxidoreductase, EC 1. ...


See also

  • Vitamin C: a discussion of the medical properties of ascorbic acid as well as its historic and social role
  • Erythorbic acid: a diastereomer of ascorbic acid.
  • Mineral ascorbates: salts of ascorbic acid
  • D-erythroascorbic acid: yeasts do not make vitamin C (L-ascorbic acid), but a similar antioxidant known as D-erythroascorbic acid

This article is about the nutrient. ... Erythorbic acid or erythorbate formerly known as isoascorbic acid and D-araboascorbic acid is a stereoisomer of ascorbic acid. ... Diastereomers (or diastereoisomers) are stereoisomers that are not enantiomers (mirror images of each other). ... Mineral Ascorbates by Richard C. Dana, Ph. ...

References

  • Clayden, Greeves, Warren, Wothers. Organic Chemistry. Oxford University Press (2001), ISBN 0-19-850346-6.
  • Derek Denby (May 1996). "Vitamin C". Chemistry Review 5 (5). 
  • Vitamin C: Its Chemistry and Biochemistry Michael B. Davies, John Austin, David A. Partridge. Royal Society of Chemistry. ISBN 0-85186-333-7
  • Food: The Chemistry of Its Components; Third Edition T.P. Coultate. Royal Society of Chemistry. ISBN 0-85404-513-9
  1. ^ Joseph Louis Svirbelf, Albert Szent-Gyorgyi The Chemical Nature Of Vitamin C, April 25th, 1932. Part of the National Library of Medicine collection. Accessed January 2007
  2. ^ Washington Post, Tainted Chinese Imports Common, published May 20, 2007
  3. ^ Newswise. "Vitamin C, water have benefits for plastic manufacturing", Reliable Plant Magazine, 2007. Retrieved on 2007-06-25. 
  4. ^ The Natural History of Ascorbic Acid in the Evolution of Mammals and Primates, Irwin Stone, 1972
  5. ^ Stone
  6. ^ Stone

The U.S. National Library of Medicine (NLM), operated by the U.S. federal government, is the worlds largest medical research library. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st Century. ... is the 176th day of the year (177th in leap years) in the Gregorian calendar. ...

External links


  Results from FactBites:
 
Ascorbic acid - Wikipedia, the free encyclopedia (906 words)
Ascorbic acid also rapidly interconverts into two unstable diketone tautomers by proton transfer, although it is the most stable in the enol form.
In this titration the NBS oxidises the ascorbic acid (in the presence of potassium iodide and starch).
Ascorbic acid and its sodium, potassium, and calcium salts are commonly used as antioxidant food additives.
Ascorbic acid (PIM 046) (2927 words)
Ascorbic acid is contraindicated in patients with hyperoxaluria (Dollery, 1991) and G-6-PD deficiency.
Ascorbic acid is readily absorbed after oral administration but the proportion does decrease with the dose (Dollery, 1979).GI absorption of ascorbic acid may be reduced in patients with diarrhoea or GI diseases.
Ascorbic acid is reported to increase the rate of mutagenesis in cultured cells but this only occurs in cultures with elevated levels of Cu or Fe This effect may be due to the ascorbate induced generation of oxygen-derived free radicals.
  More results at FactBites »

 
 

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