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Diethyl malonate
Diethyl-malonate.png
Diethyl-malonate-3D-balls.png
IUPAC name
Other names diethyl malonate, DEM
Identifiers
CAS number 105-53-3 Yes check.svgY
SMILES
Properties
Molecular formula C7H12O4
Molar mass 160.17 g/mol
Appearance colourless liquid
Density 1.05 g/cm3, liquid
Melting point

−50 °C (223 K)

Boiling point

199 °C (472 K)

Solubility in water negligible
Hazards
MSDS Oxford University MSDS
Main hazards Harmful (X), Flammable (F)
Flash point 200 °C
Related compounds
Related compounds Dimethyl malonate
Malonic acid
 Yes check.svgY (what is this?)  (verify)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
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.

Contents

Structure and properties

Malonic acid is a rather simple dicarboxylic acid, with two carboxyl groups close together in its molecule. 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)-).

Preparation

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.png

Reactions

Diethyl malonate acidity.png

The hydrogen atoms on the carbon adjacent to the a carbonyl group in a molecule is slightly more acidic than hydrogen atoms on a carbon adjacent to alkyl groups. (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.

The carbanion formed from diethyl malonate and partially stabilized by conjugation with the two adjacent carbonyl groups

This carbanion can be made from treating diethyl malonate with a base such as sodium ethoxide in ethanol. If aqueous sodium hydroxide were used, base hydrolysis of the ester can happen giving sodium malonate and ethanol. When sodium ethoxide is used, instead, any nucleophilic attack at the carboxylate by the ethoxide will not give any side product. Thus sodium ethoxide is preferred.

This carbanion is neutralized by the sodium cation from the sodium ethoxide. This resulting salt is useful in malonic ester syntheses.

Three resonance forms of the conjugate base formed by diethyl malonate

Other examples of 1,3-dicarbonyl compounds with labile hydrogens include acetylacetone and acetoacetate esters. Synthetically, malonic esters are often used in Claisen ester condensations because unwanted self-condensation reactions are avoided. Another malonate reaction is the Malonic ester synthesis which forms a monosubstituted acetic acid:

Malonic synthesis

References


Diethyl malonate
Identifiers
Abbreviations DEM
CAS number 105-53-3 Y
PubChem 7761 Y
ChemSpider 13863636 Y
UNII 53A58PA183 Y
EC number 203-305-9
MeSH Diethyl+malonate
ChEBI 391281
RTECS number OO0700000
SMILES
InChI
InChI key
Beilstein Reference 774687
Properties
Molecular formula C7H12O4
Molar mass 160.17 g/mol
Appearance colourless liquid
Density 1.05 g/cm3, liquid
Melting point

−50 °C (223 K)

Boiling point

199 °C (472 K)

Solubility in water negligible
Hazards
MSDS Oxford University MSDS
Main hazards Harmful (X), Flammable (F)
Flash point 200 °C
Related compounds
Related compounds Dimethyl malonate
Malonic acid
 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

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.

Contents

Structure and properties

Malonic acid is a rather simple dicarboxylic acid, with two carboxyl groups close together in its molecule. 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 slightly more acidic than hydrogen atoms on a carbon adjacent to alkyl groups. (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.

Thus, this compound's conjugate base is stabilized by three resonance forms below:

Preparation

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:

File:Diethyl malonate

Reactions

Malonic ester synthesis

One of the principle 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):

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

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








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