Apple acid

Malic acid
	; DL-Malic acid
Names
	Preferred IUPAC name 2-Hydroxybutanedioic acid
	Other names Hydroxybutanedioic acid; 2-Hydroxysuccinic acid; (L/D)-Malic acid; (±)-Malic acid; (S/R)-Hydroxybutanedioic acid;
Identifiers
CAS Number	6915-15-7 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:6650 ; CHEBI:30796 D-(+); CHEBI:30797 L-(–);
ChEMBL	ChEMBL1455497 ;
ChemSpider	510 ; 83793 D-(+)-malic acid ; 193317 L-(–)-malic acid ;
ECHA InfoCard	100.027.293
EC Number	230-022-8;
E number	E296 (preservatives)
IUPHAR/BPS	2480;
KEGG	C00711 ; C00497 D-(+); C00149 L-(–);
PubChem CID	525; 92824 D-(+); 222656 L-(–);
UNII	817L1N4CKP ;
CompTox Dashboard (EPA)	DTXSID0027640 ;
	InChI InChI=1S/C4H6O5/c5-2(4(8)9)1-3(6)7/h2,5H,1H2,(H,6,7)(H,8,9) Key: BJEPYKJPYRNKOW-UHFFFAOYSA-N ; InChI=1/C4H6O5/c5-2(4(8)9)1-3(6)7/h2,5H,1H2,(H,6,7)(H,8,9) Key: BJEPYKJPYRNKOW-UHFFFAOYAM;
	SMILES O=C(O)CC(O)C(=O)O;
Properties
Chemical formula	C4H6O5
Molar mass	134.09 g/mol
Appearance	Colorless
Density	1.609 g⋅cm−3
Melting point	130 °C (266 °F; 403 K)
Solubility in water	558 g/L (at 20 °C)
Acidity (pKa)	pKa1 = 3.40; pKa2 = 5.20
Hazards
	GHS labelling:
Pictograms
Flash point	203 °C
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). verify (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 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.