1,3-Cyclobutanedione
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| Template:Longitem | Template:Chembox Elements/molecular formula |
| Molar mass | Template:Chem molar mass |
| Appearance | colorless or white solid |
| Density | 1.12 g/cm3 |
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1,3-Cyclobutanedione is an organic compound with the formula Template:Chem2. 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.
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
A 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]
Ketene itself dimerizes mainly to give the lactone called diketene as well as a small amount of 1,3-cyclobutanedione.
Related compounds
- Moniliformin, a naturally occurring derivative of 3-hydroxycyclobut-2-enone