1,3-Cyclobutanedione is an organic compound with the formula (CH2)2(CO)2. It is an isomer of 1,2-cyclobutanedione. The compound would be of little interest except that its tautomer is a subunit in some commercial dyes.
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3D model (JSmol)
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CompTox Dashboard (EPA)
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Properties | |
C4H4O2 | |
Molar mass | 84.074 g·mol−1 |
Appearance | colorless or white solid |
Density | 1.12 g/cm3 |
Melting point | 119–120 °C (246–248 °F; 392–393 K) |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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In solution, 1,3-cyclobutanedione exists in equilibrium with a less stable tautomer, called squaraine , 3-hydroxycyclobut-2-enone.[1] Squaraine dyes are, formally at least, derivatives of squaraine. In such dyes, the ene-one tautomer predominates.
The mixture of tautomers can be prepared by hydrolysis of 1-ethoxycyclobutene-3-one, which is prepared from the cycloaddition of ethoxyacetylene to ketene. [2]
Substituted derivatives
editA variety of substituted 1,3-Cyclobutanediones form upon spontaneous dimerization of disubstituted ketenes.[3] 2,2,4,4-Tetramethylcyclobutanedione is thus formed by dehydrochlorination of isobutyryl chloride:[4]
- (CH3)2CHCOCl + Et3N → (CH3)2C=C=O + Et3NHCl
- 2 (CH3)2C=C=O → (CH3)2C)2(C=O)2
Ketene itself dimerizes mainly to give the lactone called diketene as well as a small amount of 1,3-cyclobutanedione.
Related compounds
edit- Moniliformin, a naturally occurring derivative of 3-hydroxycyclobut-2-enone
References
edit- ^ Morales, Giovanni; Martínez, Ramiro (2009). "Thermochemical Properties and Contribution Groups for Ketene Dimers and Related Structures from Theoretical Calculations". The Journal of Physical Chemistry A. 113 (30): 8683–8703. Bibcode:2009JPCA..113.8683M. doi:10.1021/jp9030915. PMID 19572711.
- ^ Wasserman, Harry H.; Dehmlow, Eckehard V. (1962). "Cyclobutane-1,3-Dione". Journal of the American Chemical Society. 84 (19): 3786–3787. doi:10.1021/ja00878a051.
- ^ Brady, William T. (1980). "Synthetic uses of ketenes and allenes". In Saul Patai (ed.). Ketenes, Allenes and Related Compounds: Vol. 1 (1980). PATAI'S Chemistry of Functional Groups. pp. 279–308. doi:10.1002/9780470771600.ch8. ISBN 978-0-470-77160-0.
- ^ R. Huisgen, P. Otto (1968), "The mechanism of dimerization of dimethylketene", J. Am. Chem. Soc., vol. 90, no. 19, pp. 5342–5343, doi:10.1021/ja01021a090