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.

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.

1,3-cyclobutanedione and its enol tautomer.

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]

(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.

  • Moniliformin, a naturally occurring derivative of 3-hydroxycyclobut-2-enone

References

  1. ^ 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.
  2. ^ 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.
  3. ^ 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.
  4. ^ 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
Allikas: http://en.wikipedia.org/wiki/Squaraine
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