Meldrum's acid

Structural formula
General
Surname	Meldrum's acid
other names	2,2-dimethyl-1,3-dioxane-4,6-dione
Molecular formula	C 6 H 8 O 4
External identifiers / databases
EC number	217-992-8
ECHA InfoCard	100.016.358
PubChem	16249
Wikidata	Q421283
properties
Molar mass	144.13 g mol −1
Physical state	firmly
Melting point	92-96 ° C
pK s value	4.97
safety instructions
GHS labeling of hazardous substances	no GHS pictograms
	no GHS pictograms
H and P phrases	H: no H-phrases
	P: no P-phrases
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Meldrum's acid is an organic compound named after its discoverer Andrew Norman Meldrum .

history

Assumed but incorrect structural formula of Meldrum's acid

Meldrum was the first time in 1908 by Andrew Norman Meldrum by condensation of malonic acid with acetone in acetic anhydride in the presence of sulfuric acid produced. Since Meldrum initially assumed a β- lactone with a free carboxy group , the compound is incorrectly referred to as an acid . The structure was then corrected in 1948.

properties

Meldrum's acid has a comparatively high CH-acidity having a pK _s value of 4.97. The analog of diethyl malonate in contrast, has only a pK _s to value of about. 13 Only in 2004 could this phenomenon be explained by calculations.

Because of its high CH acidity, Meldrum's acid reacts, like malonic acid, with carbonyl compounds in a Knoevenagel condensation . In the presence of pyridine, it reacts with carboxylic acid chlorides to form acyl-Meldrum's acid. If this is heated in alcohol , a β-keto ester is formed . Meldrum's acid is thus a starting compound for the synthesis of this class of substances. The β-ketoesters are used in the Knorr pyrrole synthesis .

Reaction scheme of the Knorr pyrrole synthesis

literature

Kidd, Hamish: Meldrum's Acid . In: Chemistry World , 2008, pp. 35-36.
VV Lipson, NY Gorobets: One hundred years of Meldrum's acid: advances in the synthesis of pyridine and pyrimidine derivatives , in: Molecular Diversity , 2009 , 13 (4), pp. 399-419; doi: 10.1007 / s11030-009-9136-x .
McNab, Hamish: Meldrum's Acid , in: Chemical Society Reviews , 1978 , 7 , pp. 345-358; doi: 10.1039 / CS9780700345 .

Individual evidence

↑ ^a ^b data sheet 2,2-dimethyl-1,3-dioxane-4,6-dione from Sigma-Aldrich , accessed on April 9, 2011 ( PDF ).
↑ ^a ^b Nakamura, Hirao Satoshi, Hajime Hirao, Tomohiko Ohwada: Rationale for the Acidity of Meldrum's Acid. Consistent Relation of C − H Acidities to the Properties of Localized Reactive Orbital , in: Journal of Organic Chemistry , 2004 , 69 (13), pp. 4309–4316; doi: 10.1021 / jo049456f .
↑ Andrew Norman Meldrum: A β-lactonic acid from acetone and malonic acid , in: Journal of the Chemical Society, Transactions , 1908 , 93 , pp. 598-601; doi: 10.1039 / CT9089300598 .
↑ David Davidson, Sidney A. Bernhard: The Structure of Meldrum's Supposed β-Lactonic Acid , in: Journal of the American Chemical Society , 1948 , 70 (10), pp. 3426-3428; doi: 10.1021 / ja01190a060 .
↑ Yuji Oikawa, Kiyoshi Sugano, Osamu Yonemitsu: Meldrum's acid in organic synthesis. 2. A general and versatile synthesis of β-keto esters , in: Journal of Organic Chemistry , 1978 , 43 (10), pp. 2087-2088; doi: 10.1021 / jo00404a066 .

[aldrich-1] ta sheet 2,2-dimethyl-1,3-dioxane-4,6-dione from Sigma-Aldrich , accessed on April 9, 2011 ( PDF ).

[Ohwada-2] Nakamura, Hirao Satoshi, Hajime Hirao, Tomohiko Ohwada: Rationale for the Acidity of Meldrum's Acid. Consistent Relation of C − H Acidities to the Properties of Localized Reactive Orbital , in: Journal of Organic Chemistry , 2004 , 69 (13), pp. 4309–4316; doi: 10.1021 / jo049456f .

[3] Andrew Norman Meldrum: A β-lactonic acid from acetone and malonic acid , in: Journal of the Chemical Society, Transactions , 1908 , 93 , pp. 598-601; doi: 10.1039 / CT9089300598 .

[4] David Davidson, Sidney A. Bernhard: The Structure of Meldrum's Supposed β-Lactonic Acid , in: Journal of the American Chemical Society , 1948 , 70 (10), pp. 3426-3428; doi: 10.1021 / ja01190a060 .

[5] Yuji Oikawa, Kiyoshi Sugano, Osamu Yonemitsu: Meldrum's acid in organic synthesis. 2. A general and versatile synthesis of β-keto esters , in: Journal of Organic Chemistry , 1978 , 43 (10), pp. 2087-2088; doi: 10.1021 / jo00404a066 .