(S)-malate
 |
|
 |
|
DL-Malic acid
|
|
| Names | |
|---|---|
|
Preferred IUPAC name
2-Hydroxybutanedioic acid
|
|
| Other names
Hydroxybutanedioic acid
2-Hydroxysuccinic acid L-Malic acid D-Malic acid (–)-Malic acid (+)-Malic acid (S)-Hydroxybutanedioic acid (R)-Hydroxybutanedioic acid |
|
| Identifiers | |
|
3D model (JSmol)
|
|
| ChEBI | |
| ChemSpider | |
| ECHA InfoCard | 100.027.293 |
| EC Number | 230-022-8 |
| E number | E296 (preservatives) |
| KEGG | |
|
PubChem CID
|
|
| UNII | |
|
|
|
|
| Properties | |
| C4H6O5 | |
| Molar mass | 134.09 g·mol−1 |
| Density | 1.609 g cm−3 |
| Melting point | 130 °C (266 °F; 403 K) |
| 558 g/L (at 20 °C) | |
| Acidity (pKa) | pKa1 = 3.40, pKa2 = 5.20 |
| Related compounds | |
|
Other anions
|
malate |
|
Related carboxylic acids
|
succinic acid tartaric acid fumaric acid |
|
Related compounds
|
butanol butyraldehyde crotonaldehyde sodium malate |
|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|
|
 (what is   ?) |
|
| Infobox references | |
Malic acid is an organic compound with the molecular formula C4H6O5. It is a dicarboxylic acid that is made by all living organisms, contributes to the pleasantly sour taste of fruits, and is used as a food additive. Malic acid has two stereoisomeric forms (L- and D-enantiomers), though only the L-isomer exists naturally. The salts and esters of malic acid are known as malates. The malate anion is an intermediate in the citric acid cycle.
L-Malic acid is the naturally occurring form, whereas a mixture of L- and D-malic acid is produced synthetically.
Malate plays an important role in biochemistry. In the C4 carbon fixation process, malate is a source of CO2 in the Calvin cycle. In the citric acid cycle, (S)-malate is an intermediate, formed by the addition of an -OH group on the si face of fumarate. It can also be formed from pyruvate via anaplerotic reactions.
Malate is also synthesized by the carboxylation of phosphoenolpyruvate in the guard cells of plant leaves. Malate, as a double anion, often accompanies potassium cations during the uptake of solutes into the guard cells in order to maintain electrical balance in the cell. The accumulation of these solutes within the guard cell decreases the solute potential, allowing water to enter the cell and promote aperture of the stomata.
Malic acid was first isolated from apple juice by Carl Wilhelm Scheele in 1785.Antoine Lavoisier in 1787 proposed the name , which is derived from the Latin word for apple, —as is its genus name Malus. In German it is named (or Apfelsäure) after plural or singular of the fruit apple, but the salt(s) Malat(e). Malic acid contributes to the sourness of green (unripe) apples. It is present in grapes and in most wines with concentrations sometimes as high as 5 g/l. It confers a tart taste to wine, although the amount decreases with increasing fruit ripeness. The taste of malic acid is very clear and pure in rhubarb, a plant for which it is the primary flavor. It is also a component of some artificial vinegar flavors, such as "salt and vinegar" flavored potato chips.
...
Wikipedia