Diethyl malonate

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Diethyl malonate
Diethyl-malonate.png
Diethyl-malonate-3D-balls.png
Identifiers
Abbreviations DEM
CAS number 105-53-3 YesY
PubChem 7761 YesY
ChemSpider 13863636 YesY
UNII 53A58PA183 YesY
EC number 203-305-9
MeSH Diethyl+malonate
ChEBI CHEBI:391281 N
ChEMBL CHEMBL177114 YesY
RTECS number OO0700000
Beilstein Reference 774687
Jmol-3D images Image 1
Properties
Molecular formula C7H12O4
Molar mass 160.17 g/mol
Appearance colourless liquid
Density 1.05 g/cm3, liquid
Melting point −50 °C (−58 °F; 223 K)
Boiling point 199 °C (390 °F; 472 K)
Solubility in water negligible
Hazards
MSDS Oxford University MSDS
Main hazards Harmful (X), Flammable (F)
Flash point 200 °C (392 °F; 473 K)
Related compounds
Related compounds Dimethyl malonate
Malonic acid
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N (verify) (what is: YesY/N?)
Infobox references

Diethyl malonate, also known as DEM, is the diethyl ester of malonic acid. It occurs naturally in grapes and strawberries as a colourless liquid with an apple-like odour, and is used in perfumes. It is also used to synthesize other compounds such as barbiturates, artificial flavourings, vitamin B1, and vitamin B6.

Structure and properties[edit]

Malonic acid is a rather simple dicarboxylic acid, with two the carboxyl groups close together. In forming diethyl malonate from malonic acid, the hydroxyl group (-OH) on both of the carboxyl groups is replaced by an ethoxy group (-OEt; -OCH2CH3). The methylene group (-CH2-) in the middle of the malonic part of the diethyl malonate molecule is neighboured by two carbonyl groups (-C(=O)-).[1]

The hydrogen atoms on the carbon adjacent to the carbonyl group in a molecule is significantly more acidic than hydrogen atoms on a carbon adjacent to alkyl groups (up to 30 orders of magnitude). (This is known as the α position with respect to the carbonyl.) The hydrogen atoms on a carbon adjacent to two carbonyl groups are even more acidic because on the – the carbonyl groups helps stabilize the carbanion resulting from the removal of a proton from the methylene group between them.

Diethyl malonate acidity.png

The extent of resonance stabilization of this compound's conjugate base is depicted by the three resonance forms below:

Diethyl malonate resonance.svg

Preparation[edit]

Diethyl malonate may be prepared by reacting the sodium salt of chloroacetic acid with sodium cyanide, followed by base hydrolysis of the resultant nitrile to give the sodium salt malonic acid. Fischer esterification gives diethyl malonate:

Diethyl malonate synthesis.svg

Reactions[edit]

Malonic ester synthesis[edit]

One of the principal uses of this compound is in the malonic ester synthesis. The carbanion (2) formed by reacting diethyl malonate (1) with a suitable base can be alkylated with a suitable electrophile. This alkylated 1,3-dicarbonyl compound (3) readily undergoes decarboxylation with loss of carbon dioxide, to give a substituted acetic acid (4):

Malonic synthesis

Sodium ethoxide is preferred as the base. The use of aqueous sodium hydroxide may give the base hydrolysis products: sodium malonate and ethanol. In comparison, when sodium ethoxide is used, any nucleophilic attack at the carboxylate by the ethoxide will not give any side product; other alkoxide salts will cause scrambling by transesterification.

Other reactions[edit]

Like many other esters, this compound undergoes the Claisen ester condensations. The advantage of using this compound is that unwanted self-condensation reactions are avoided. Like other esters, this compound undergoes bromination at the alpha position.[2]

References[edit]

  1. ^ IR spectrum of Malonic acid
  2. ^ C. S. Palmer and P. W. McWherter, "Ethyl Bromomalonate", Org. Synth. ; Coll. Vol. 1: 245