Question

how butenoic acid is prepared from diethyl malonate

Answer 1

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.
Diethyl malonateNamesPreferred IUPAC name

Diethyl propanedioate

Other names

Diethyl malonate

Identifiers

CAS Number

105-53-3 

3D model (JSmol)

Interactive image

AbbreviationsDEM

Beilstein Reference

774687ChEBI

CHEBI:391281 

ChEMBL

ChEMBL177114 

ChemSpider

13863636 

ECHA InfoCard100.003.006EC Number203-305-9MeSHDiethyl+malonate

PubChem CID

7761

RTECS numberOO0700000UNII

53A58PA183

reaction
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):
 
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.