ascorbic acid

(10)6(11)12-5/h2,5,7-8,10-

11H,1H2/t2-,5+/m0/s1 ChemSpider ID 10189562 Properties Molecular formula C6H8O6 Molar mass 176.12 g mol-1 Appearance White or light yellow solid Density 1.65 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) 4.17 (first), 11.6 (second) Hazards MSDS ScienceLab.com LD50 11.9 g/kg (oral, rat)[1] Except where noted otherwise, data are given for

materials in their standard state

(at 25 °C, 100 kPa)

Infobox references

Ascorbic acid is a sugar 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.[2] Contents [hide] 1 Chemistry 1.1 Acidity 1.2 Tautomerism 1.3 Determination 2 Uses 3 Antioxidant mechanism 4 Ascorbic acid synthesis in non-primates 5 See also 6 References 7 External links //

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. There are two resonance structures for the deprotonated form, differing in the position of the double bond.

Another way to look at ascorbic acid is to consider it as an enol. The deprotonated form is an enolate, which is usually strongly basic. However, the adjacent double bond stabilizes the deprotonated form. Movement of electron pairs in deprotonation

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

Ascorbic acid also 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.