malonic acid

Malonic acid
IUPAC name	propanedioic acid
Other names	methanedicarboxylic acid
Identifiers
CAS number	141-82-2 Y
PubChem	867
SMILES	O=C(O)CC(O)=O
Properties
Molecular formula	C3H4O4
Molar mass	104.03 g/mol
Exact mass	104.010959
Density	1,619 g/cm3, Solid
Melting point	135–136 °C (408–409 K)
Boiling point	decomposes
Solubility in water	full
Acidity (pKa)	pKa1=2.83 pKa2=5.69
Related compounds
Other anions	malonate
Related carboxylic acids	acetic acid oxalic acid propionic acid tartronic acid acrylic acid butyric acid succinic acid fumaric acid
Related compounds	propanone propionaldehyde propanedial dimethyl malonate
Hazards
MSDS	External MSDS
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Malonic acid (IUPAC systematic name: propanedioic acid) is a dicarboxylic acid with structure CH₂(COOH)₂. The ionised form of malonic acid, as well as its esters and salts, are known as malonates. For example, diethyl malonate is malonic acid's ethyl ester. The name originates from Latin malum, meaning apple.

Biochemistry

The calcium salt of malonic acid occurs in high concentrations in beetroot. It exists in its normal state as white crystals. Malonic acid is the archetypal example of a competitive inhibitor: it acts against succinate dehydrogenase (complex II) in the respiratory electron transport chain.

Preparation

A classical preparation of malonic acid starts from chloroacetic acid:^[1]

This acid is chlorinated to chloroacetic acid. Sodium carbonate generates the sodium salt which is then reacted with sodium cyanide to the cyano acetic acid salt in a nucleophilic substitution. The nitrile group can be hydrolysed with sodium hydroxide to sodium malonate and acidification affords malonic acid.

Organic reactions

In a well known reaction malonic acid condenses with urea to barbituric acid. Malonic acid is frequently used as an enolate in Knoevenagel condensations or condensed with acetone to form Meldrum's acid. Its esters are also used for the ^-CH₂COOH synthon in the malonic ester synthesis.

External links

• pH-Spectrum of Disodium Malonate
• pH-Spectrum of Malonate-copper-complex
• Calculator: Water and solute activities in aqueous malonic acid

References

1. ^ Nathan Weiner, "Malonic acid", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv2p0376 ; Coll. Vol. 2: 376