1,3-Cyclobutanedione

1,3-Cyclobutanedione
Identifiers
CAS Number	1,3-cyclobutanedione tautomer: 15506-53-3; 3-hydroxycyclobut-2-enone: 78675-98-6;
3D model (JSmol)	1,3-cyclobutanedione tautomer: Interactive image; 3-hydroxycyclobut-2-enone: Interactive image;
ChemSpider	1,3-cyclobutanedione tautomer: 25456; 3-hydroxycyclobut-2-enone: 10004000;
PubChem CID	1,3-cyclobutanedione tautomer: 27357; 3-hydroxycyclobut-2-enone: 11829353;
CompTox Dashboard (EPA)	1,3-cyclobutanedione tautomer: DTXSID80165803 ; 3-hydroxycyclobut-2-enone: DTXSID30473940;
	InChI InChI=1S/C4H4O2/c5-3-1-4(6)2-3/h1-2H2 Key: PZQGSZRQKQZCOJ-UHFFFAOYSA-N; 3-hydroxycyclobut-2-enone: InChI=1S/C4H4O2/c5-3-1-4(6)2-3/h1,5H,2H2 Key: IHXWECHPYNPJRR-UHFFFAOYSA-N;
	SMILES 1,3-cyclobutanedione tautomer: C1C(=O)CC1=O; 3-hydroxycyclobut-2-enone: C1C(=CC1=O)O;
Properties
Chemical formula	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). Infobox references

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.

Related compounds

Moniliformin, a naturally occuring derivative of 3-hydroxycyclobut-2-enone

References

^ 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

[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

[1]

[2]

[3]

[4]