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This article deals with the molecular aspects of ascorbic acid. For information about its purpose in nutrition, see Vitamin C. Vitamin C or L-ascorbate is an Essential nutrient for a large number of higher primate species a small number of other Mammalian
Ascorbic acid
IUPAC name (R)-3,4-dihydroxy-5-((S)- 1,2-dihydroxyethyl)furan-2(5H)-one
Identifiers
CAS number [50-81-7]
PubChem 5785
EINECS number 200-066-2
InChI 1/C6H8O6/c7-1-2(8)5-3(9)4
(10)6(11)12-5/h2,5,7-8,10-
11H,1H2/t2-,5+/m0/s1
Properties
Molecular formula C6H8O6
Molar mass 176. 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 They are also referred to PubChem is a Database of chemical Molecules The system is maintained by the National Center for Biotechnology Information (NCBI a component The EINECS number (for European Inventory of Existing Chemical Substances) is a registry number given to each Chemical substance commercially available in the The IUPAC International Chemical Identifier ( InChI, pronounced "INchee" is a textual Identifier for Chemical substances designed to provide a 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 Molar mass, symbol M, is the Mass of one mole of a substance ( Chemical element or Chemical compound) 1241 g/mol
Appearance White or light yellow solid
Density 1. The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different 65 g/cm³
Melting point

190-192 °C, 463-465 K, 374-378 °F (decomposes)
Solubility in water 33g/100ml
Solubility in ethanol 2g/100ml
Solubility in glycerol 1g/100ml
Solubility in propylene glycol 5g/100ml
Solubility in diethyl ether, chloroform, benzene, petroleum ether, oils, fats, fat solvents insoluble
Acidity (pKa) 4. The melting point of a solid is the temperature range at which it changes state from solid to Liquid. Solubility is the characteristic Physical property referring to the ability of a given substance the Solute, to dissolve in a Solvent. Water is a common Chemical substance that is essential for the survival of all known forms of Life. Solubility is the characteristic Physical property referring to the ability of a given substance the Solute, to dissolve in a Solvent. Solubility is the characteristic Physical property referring to the ability of a given substance the Solute, to dissolve in a Solvent. Solubility is the characteristic Physical property referring to the ability of a given substance the Solute, to dissolve in a Solvent. Propylene glycol, known also by the systematic name propane-12-diol is an Organic compound (a Diol Alcohol) usually a faintly sweet odorless and Solubility is the characteristic Physical property referring to the ability of a given substance the Solute, to dissolve in a Solvent. 17 (first), 11. 6 (second)
Hazards
MSDS ScienceLab.com
LD50 11. A material safety data sheet ( MSDS) is a form containing data regarding the properties of a particular substance In Toxicology, the median lethal dose, LD50 (abbreviation for “Lethal Dose 50%” or LCt50 (Lethal Concentration & Time of a 9 g/kg (oral, rat)[1]
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)
Infobox disclaimer and references

Ascorbic acid is a sugar acid with antioxidant properties. In Chemistry, the standard state of a material is its state at 1 bar (100 Kilopascals exactly Sugar acids are Monosaccharides that have had an -OH group oxidized to a carboxyl group. An antioxidant is a Molecule capable of slowing or preventing the oxidation of other molecules 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. In Chemistry, an enantiomer ( from the Greek ἐνάντιος opposite and μέρος part or portion is one of two Stereoisomers that are nonsuperimposable Vitamin C or L-ascorbate is an Essential nutrient for a large number of higher primate species a small number of other Mammalian The name is derived from the alpha privative a- (meaning no) and scorbuticus (scurvy), the disease caused by a deficiency of vitamin C. The privative a (also known as privative alpha or α privativum) is the prefix a- which expresses negation or absence (e Scurvy (NLat scorbutus is a disease resulting from a deficiency of Vitamin C, which is required for the synthesis of Collagen in humans 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. Year 1937 ( MCMXXXVII) was a Common year starting on Friday (link will display the full calendar of the Gregorian calendar. The Nobel Prize (Nobelpriset (Nobelprisen is a Swedish prize established in the 1895 will of Swedish chemist Alfred Nobel; it was first awarded in Peace, Literature Sir Walter Norman Haworth ( March 19, 1883, Chorley, Lancashire &ndash March 19, 1950, Barnt Green, Paul Karrer ( April 21, 1889 &ndash June 18, 1971) was a Swiss Organic chemist best known for his work on Vitamins A vitamin is an Organic compound required as a Nutrient in tiny amounts by an Organism. Albert Szent-Györgyi de Nagyrápolt ( September 16, 1893 &ndash October 22, 1986) was a Hungarian Physiologist who At the time of its discovery in the 1920s, it was called hexuronic acid by some researchers. [2]

Contents

Chemistry

Acidity

Ascorbic acid, the formula of which is C6H8O6, behaves as a vinylogous carboxylic acid, wherein the double bond ("vinyl") transmits electron pairs between the hydroxyl and the carbonyl. Vinylogous reactivity is the behavior of a Vinyl group in Conjugation with an Electron-withdrawing group analogous to the reactions of the electron-withdrawing Carboxylic acids are Organic acids characterized by the presence of a Carboxyl group, which has the formula -C(=OOH usually written -COOH or -CO2H There are two resonance structures for the deprotonated form, differing in the position of the double bond. Resonance in Chemistry is a theory used to represent and model certain types of non-classical Molecular structures Resonance is a key component

Another way to look at ascorbic acid is to consider it as an enol. Enols (also known as alkenols) are Alkenes with a Hydroxyl group affixed to one of the carbon atoms composing the Double bond. The deprotonated form is an enolate, which is usually strongly basic. Enols (also known as alkenols) are Alkenes with a Hydroxyl group affixed to one of the carbon atoms composing the Double bond. However, the adjacent double bond stabilizes the deprotonated form.

Movement of electron pairs in deprotonation
Movement of electron pairs in deprotonation


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. In Chemistry, a nucleophile (literally nucleus lover as in nucleus and phile) is a Reagent that forms a Chemical bond to A diketone is a molecule containing two Ketone groups The simpliest diketone is Diacetyl, also known as 23-butanedione Tautomers are Organic compounds that are interconvertible by a Chemical reaction called tautomerization. The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive The proton of the enol is lost, and reacquired by electrons from the double bond, to produce a diketone. This is an enol reaction. Enols (also known as alkenols) are Alkenes with a Hydroxyl group affixed to one of the carbon atoms composing the Double bond. There are two possible forms: 1,2-diketone and 1,3-diketone.

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 is a common laboratory method of Quantitative chemical analysis that is used to determine the unknown Concentration of a known Reactant An oxidizing agent or oxidising agent (also called an oxidant, oxidizer or oxidiser) can be defined as either a Chemical compound

DCPIP

A commonly-used oxidising agent is the dye 2,6-dichlorophenol-indophenol, or DCPIP for short. 26-dichlorophenolindophenol, ( DCPIP) is a blue Chemical compound used as a redox dye. The blue dye is run into the ascorbic acid solution until a faint pink colour persists for 15 seconds. In Chemistry, a solution is a Homogeneous Mixture composed of two or more substances

Iodine

Another method involves using iodine and a starch indicator, wherein 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. Iodine (ˈaɪədaɪn ˈaɪədɪn or /ˈaɪədiːn/ from ιώδης iodes "violet" is a Chemical element that has the symbol I and Atomic Starch, CAS # 9005-25-8 Chemical formula (C6H10O5n is a Polysaccharide This indicates the end-point of the titration. As an alternative, ascorbic acid can be reacted with iodine in excess, followed by back titration with sodium thiosulfate while using starch as an indicator.

Iodate and iodine

The above method involving iodine requires making up and standardising the iodine solution. One way around 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. In the iodate Anion, Iodine is bonded to three Oxygen atoms and the Molecular formula In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are

N-Bromosuccinimide

A much-less-common oxidising agent is N-bromosuccinimide, (NBS). N -Bromosuccinimide or NBS is a Chemical reagent which is used in Radical substitution and Electrophilic addition reactions In this titration, the NBS oxidises the ascorbic acid (in the presence of potassium iodide and starch). Potassium iodide is an Inorganic compound with formula K[[iodide I]] 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.

Uses

Top: ascorbic acid
(reduced form of Vitamin C)
Bottom: dehydroascorbic acid
(oxidized form of Vitamin C)

Ascorbic acid is easily oxidized and so is used as a reductant in photographic developer solutions (among others) and as a preservative. A reducing agent (also called a reductant or reducer) is the element or a compound in a Redox (reduction-oxidation reaction (see Electrochemistry Vitamin C or L-ascorbate is an Essential nutrient for a large number of higher primate species a small number of other Mammalian Dehydroascorbic acid ( DHA) is an oxidized form of Ascorbic acid. An oxidizing agent or oxidising agent (also called an oxidant, oxidizer or oxidiser) can be defined as either a Chemical compound Vitamin C or L-ascorbate is an Essential nutrient for a large number of higher primate species a small number of other Mammalian A preservative is a natural or synthetic chemical that is added to products such as foods pharmaceuticals paints biological samples wood etc

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

The L-enantiomer of ascorbic acid is also known as vitamin C. The term chiral (pronounced /ˈkaɪɹ(əl̩/ is used to describe an object that is non- superimposable on its mirror image Vitamin C or L-ascorbate is an Essential nutrient for a large number of higher primate species a small number of other Mammalian The name "ascorbic" comes from its property of preventing and curing scurvy. Scurvy (NLat scorbutus is a disease resulting from a deficiency of Vitamin C, which is required for the synthesis of Collagen in humans 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. A primate is a member of the biological order Primates ( Latin: "prime first rank" the group that contains Lemurs the Aye-aye The Guinea pig (also commonly called the cavy after its scientific name Cavia porcellus) is a species of Rodent belonging to the family Caviidae

Ascorbic acid and its sodium, potassium, and calcium salts are commonly used as antioxidant food additives. A salt, in Chemistry, is defined as the product formed from the neutralisation reaction of Acids and bases. An antioxidant is a Molecule capable of slowing or preventing the oxidation of other molecules Food additives are substances added to food to preserve flavour or improve its taste and appearance 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. Fats consist of a wide group of compounds that are generally soluble in organic solvents and largely insoluble in water Solubility is the characteristic Physical property referring to the ability of a given substance the Solute, to dissolve in a Solvent. Esters are a class of Chemical compounds and Functional groups Esters consist of an inorganic or organic Acid in which at least In Chemistry, especially Biochemistry, a fatty acid is a Carboxylic acid often with a long unbranched Aliphatic tail ( chain) which Eighty percent of the world's supply of ascorbic acid is produced in China. [3]

The relevant European food additive E numbers are:

  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. E numbers are number codes for Food additives and are usually found on Food labels throughout the European Union. Mineral ascorbates are salts of Ascorbic acid (aka Vitamin C) Mineral ascorbates are salts of Ascorbic acid (aka Vitamin C) Mineral ascorbates are salts of Ascorbic acid (aka Vitamin C) Ascorbyl palmitate is an Ester formed from Ascorbic acid and Palmitic acid creating a fat-soluble form of vitamin C Ascorbyl stearate (C24H42O7 is an Ester formed from Ascorbic acid and Stearic acid.

It can be added to water that has been treated with iodine to make it potable, neutralizing the unpleasant iodine taste, and increasing the health benefits of drinking water, although increasing the chance of tooth decay. Water is a common Chemical substance that is essential for the survival of all known forms of Life. Dental caries is a disease that damages Tooth structures resulting in what is commonly called tooth decay or cavities which are holes in the teeth

In plastic manufacturing, ascorbic acid can be used to assemble molecular chains more quickly and with less waste than traditional synthesis methods. [4]

Antioxidant mechanism

Ascorbate acts as an antioxidant by being 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. Reactive oxygen species (ROS are ions or very small molecules that include Oxygen Ions free radicals, and Peroxides both inorganic and Hydrogen peroxide (H2O2 is a very pale blue liquid which appears colorless in a dilute solution slightly more Viscous than water This is due to their interaction with nucleic acid, proteins, and lipids. A nucleic acid is a Macromolecule composed of chains of monomeric Nucleotides In Biochemistry these Molecules carry Genetic information 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.

Ascorbic acid synthesis in non-primates

Ascorbic acid is found in plants, animals, and single-cell organisms. [5] All living animals either make it, eat it, or die from scurvy due to lack of it. Scurvy (NLat scorbutus is a disease resulting from a deficiency of Vitamin C, which is required for the synthesis of Collagen in humans 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. L-gulonolactone oxidase ( EC 1138 is an Enzyme that Catalyzes the reaction of D- Glucuronolactone [6] 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 [7] 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.

See also

References

  1. ^ Safety (MSDS) data for ascorbic acid. Oxford University (2005-10-09). The University of Oxford (informally "Oxford University" or simply "Oxford" located in the city of Oxford, Oxfordshire, England is the Year 2005 ( MMV) was a Common year starting on Saturday (link displays full calendar of the Gregorian calendar. Events 768 - Carloman I and Charlemagne are crowned Kings of The Franks. Retrieved on 2007-02-21. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 362 - Athanasius returns to Alexandria. 1245 - Thomas, the first known Bishop of Finland
  2. ^ Joseph Louis Svirbelf, Albert Szent-Gyorgyi The Chemical Nature Of Vitamin C, April 25, 1932. Events 1607 - Eighty Years' War: The Dutch fleet destroys the anchored Spanish fleet at Gibraltar. Year 1932 ( MCMXXXII) was a Leap year starting on Friday of the Gregorian calendar. Part of the National Library of Medicine collection. The United States National Library of Medicine ( NLM) operated by the United States federal government, is the world's largest Medical library. Accessed January 2007
  3. ^ Washington Post, Tainted Chinese Imports Common, published May 20, 2007
  4. ^ Newswise. Events 325 - The First Council of Nicaea &ndash the first Ecumenical Council of the Christian Church is held Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. "Vitamin C, water have benefits for plastic manufacturing", Reliable Plant Magazine, 2007. Retrieved on 2007-06-25. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 524 - Battle of Vézeronce, the Franks defeat the Burgundians  
  5. ^ The Natural History of Ascorbic Acid in the Evolution of Mammals and Primates, Irwin Stone, 1972
  6. ^ Stone
  7. ^ Stone

External links

Dictionary

ascorbic acid

-noun

  1. A white crystalline organic compound, C6H8O6, found in citrus fruits and many vegetables; it is an antioxidant and an efficient scavenger of free radicals.
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