Diethyl malonate
Structural formula | |||||||||||||||||||
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General | |||||||||||||||||||
Surname | Diethyl malonate | ||||||||||||||||||
other names |
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Molecular formula | C 7 H 12 O 4 | ||||||||||||||||||
Brief description |
colorless liquid with an aromatic odor |
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properties | |||||||||||||||||||
Molar mass | 160.17 g · mol -1 | ||||||||||||||||||
Physical state |
liquid |
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density |
1.05 g cm −3 |
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Melting point |
−50 ° C |
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boiling point |
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Vapor pressure |
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solubility |
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Refractive index |
1.414 (20 ° C) |
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safety instructions | |||||||||||||||||||
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Toxicological data | |||||||||||||||||||
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C |
Diethyl malonate is a colorless, pleasant-smelling liquid that is one of the esters .
Extraction and presentation
Diethyl malonate cannot be obtained from the free acid by esterification with ethanol because malonic acid breaks down at elevated temperatures to form acetic acid and CO 2 ( decarboxylation ). The sodium salt of cyanoacetic acid has to be reacted with ethanol and concentrated mineral acids to produce it.
properties
Physical Properties
Diethyl malonate is a colorless liquid that boils at 199 ° C under normal pressure . According to Antoine, the vapor pressure function results from log 10 (P) = A− (B / (T + C)) (P in bar, T in K) with A = 5.90564, B = 2864.822 and C = 13.407 im Temperature range from 313 to 472 K. Miscibility with water is limited. As the temperature rises, the solubility of diethyl malonate in water falls to about 50 ° C. and then increases again or the solubility of water in diethyl malonate increases.
Solubilities between diethyl malonate and water temperature ° C 0 9.1 20.0 31.0 39.6 49.9 60.2 70.5 81.0 90.6 Diethyl malonate in water in% 3.09 2.80 2.26 2.10 2.09 2.05 2.12 2.18 2.33 2.47 Water in diethyl malonate in% 1.09 1.28 1.60 1.92 2.16 2.62 2.91 3.63 4.02 4.30
Chemical properties
The methylene protons of diethyl malonate are slightly acidic; therefore it can with strong bases such as B. sodium ethanolate are deprotonated. This deprotonated form is a carbanion and can be converted with alkyl halides to alkyl-substituted malonic acid diethyl esters ( malonic ester synthesis ). Other possible reactions of this carbanion:
- Reaction with carbonyl derivatives ( aldehydes or ketones ) leads to aldol products
- Reaction with carboxylic acid derivatives leads to acylation
Safety-related parameters
Diethyl malonate forms flammable vapor-air mixtures at elevated temperatures. The compound has a flash point of 85 ° C. The explosion range is between 0.8 vol.% As the lower explosion limit (LEL) and 12.8 vol.% As the upper explosion limit (UEL). The ignition temperature is 435 ° C. The substance therefore falls into temperature class T2.
use
If alkyl-substituted malonic acid diethyl esters are hydrolyzed to give the corresponding alkylated malonic acids and then heated, they decarboxylate like malonic acid itself; substituted acetic acid derivatives are formed with the elimination of carbon dioxide (see malonic ester synthesis ). Alkyl-substituted malonic acid diethyl esters can also be reacted with urea to form barbituric acid derivatives . The reaction is related to the Knoevenagel reaction .
Individual evidence
- ↑ a b c data sheet diethyl malonate (PDF file; 73 kB) from SysKem Chemiehandel GmbH, accessed on January 23, 2016.
- ↑ a b c d e f g h i j k Entry on diethyl malonate in the GESTIS substance database of the IFA , accessed on November 8, 2017(JavaScript required) .
- ↑ a b c d D'Ans-Lax, paperback for chemists and physicists, volume 2, third edition 1964.
- ↑ a b c Data sheet Diethyl malonate from Sigma-Aldrich , accessed on November 4, 2016 ( PDF ).
- ↑ Entry on diethyl malonate. In: Römpp Online . Georg Thieme Verlag, accessed on January 2, 2015.
- ^ Stull, DR: Vapor Pressure of Pure Substances. Organic and Inorganic Compounds in Ind. Eng. Chem. 39 (1947) 517-540, doi : 10.1021 / ie50448a022
- ^ A b R. M. Stephenson: Mutual Solubilities: Water-Ketones, Water-Ethers, and Water-Gasoline-Alcohols in J. Chem. Eng. Data 37 (1992) 80-95, doi : 10.1021 / je00005a024 .