Cyclopropanone

Cyclopropanone has been prepared by reaction of ketene with diazomethane in an unreactive solvent such as dichloromethane. 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: :(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. The isocyanate adducts can also be prepared directly through photochemical rearrangement of succinimino ethers. ==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. 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) cycloaddition|[4+3] cycloadditions, for instance with cyclic dienes such as furan. 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: : 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. ==See also==