Cyclopropanone
Chemical compound
From Wikipedia, the free encyclopedia
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]
| |
| Names | |
|---|---|
| Preferred IUPAC name
Cyclopropanone | |
| Identifiers | |
3D model (JSmol) |
|
| ChemSpider | |
PubChem CID |
|
CompTox Dashboard (EPA) |
|
| |
| |
| Properties | |
| C3H4O | |
| Molar mass | 56.064 g·mol−1 |
| 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).
| |
Preparation
Cyclopropanone has been prepared by reaction of ketene with diazomethane[1][2] in an unreactive solvent such as dichloromethane.[3] 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:[4][5]
- (CH2)2CO + X-H → (CH2)2C(X)(OH) (X-H = R2N-H, HO-H, RO-H)
This reaction underlies cyclopropanone's polymerization at room temperature, initiated by traces of water.[1]: 1476 The isocyanate adducts can also be prepared directly through photochemical rearrangement of succinimino ethers.[1]: 1462
Structure
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.
Derivatives
Cyclopropanones are intermediates in the Favorskii rearrangement with cyclic ketones where carboxylic acid formation is accompanied by ring-contraction.
Cyclopropanones react as dienophiles in [4+3] cycloadditions, for instance with cyclic dienes such as furan.[1]: 1492–1493 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.[6]
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:[7]
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).
Coprine
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.[8]
See also
- Other cyclic ketones: cyclobutanone, cyclopentanone, cyclohexanone
- Other cyclopropane derivatives: cyclopropene, cyclopropenone