Cyclopropanone is an organic compound with molecular formula (CH2)2CO consisting of a cyclopropane carbon framework with a ketone functional group. The parent compound is labile, being highly sensitive toward even weak nucleophiles. Surrogates of cyclopropanone include the ketals.[1]
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Cyclopropanone | |
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C3H4O | |
Molar mass | 56.06326 |
Appearance | colorless |
Density | 0.867 g/mL at 25 °C |
Melting point | −90 °C (−130 °F; 183 K) |
Boiling point | 50 to 53 °C (122 to 127 °F; 323 to 326 K) at 22 mmHg |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Cyclopropanone has been prepared by reaction of ketene with diazomethane.[1][2] These solutions are stable at −78 °C. In the presence of protic reagents such as carboxylic acids, primary and secondary amines, and alcohols, cyclopropanone converts to adducts, which are often isolatable at room temperature:[3][4]
(X-H = R2N-H, HO-H, RO-H)
The C3O atoms are coplanar. As deduced from the microwave spectrum, the H2C-CH2 bond length of 157.5 pm is unusually long. By contrast, the C-C bond lengths in cyclopropane are 151 pm. The C=O bond length of 119 pm is short compared to the 123 pm bond length in acetone.[1]
The value of νC=O in the infrared spectrum is near 1815 cm−1, ca. 70 cm−1 higher than values for a typical ketone.
Cyclopropanones are intermediates in the Favorskii rearrangement with cyclic ketones where carboxylic acid formation is accompanied by ring-contraction.
Cyclopropanones react as 1,3-dipoles in cycloadditions for instance with cyclic dienes such as furan.[1] An oxyallyl intermediate or valence tautomer (formed by cleavage of the C2-C3 bond) is suggested as the active intermediate or even a biradical structure (compare to the related trimethylenemethane).
Other reactions of cyclopropanones take place through this intermediate. For instance enantiopure (+)-trans-2,3-di-tert-butylcyclopropanone racemizes when heated to 80 °C.[5]
An oxyallyl intermediate is also proposed in the photochemical conversion of a 3,5-dihydro-4H-pyrazole-4-one with expulsion of nitrogen to an indane:[6]
In this reaction oxyallyl intermediate A, in chemical equilibrium with cyclopropanone B attacks the phenyl ring through its carbocation forming a transient 1,3-cyclohexadiene C (with UV trace similar to isotoluene) followed by rearomatization. The energy difference between A and B is 5 to 7 kcal/mol (21 to 29 kJ/mol).
The cyclopropanone derivative 1-aminocyclopropanol occurs naturally by hydrolyzes of coprine, a toxin in some mushrooms. 1-Aminocyclopropanol is an inhibitor of the enzyme acetaldehyde dehydrogenase.[7]