Cyclopropanone

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]

Cyclopropanone

Names
Preferred IUPAC name Cyclopropanone
Identifiers
CAS Number	5009-27-8 Y
3D model (JSmol)	Interactive image Interactive image
ChemSpider	122027 Y
PubChem CID	138404
CompTox Dashboard (EPA)	DTXSID30198202
InChI InChI=1S/C3H4O/c4-3-1-2-3/h1-2H2 Y Key: VBBRYJMZLIYUJQ-UHFFFAOYSA-N Y InChI=1/C3H4O/c4-3-1-2-3/h1-2H2 Key: VBBRYJMZLIYUJQ-UHFFFAOYAV
SMILES C1CC1=O O=C1CC1
Properties
Chemical formula	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). Y verify (what is YN ?) Infobox references

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)

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 ν_C=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 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.^[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