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 and bonding
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.
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-cyclohexadieneC (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).
^ abcdWasserman, Harry H.; Berdahl, Donald R.; Lu, Ta-Jung (1987). "The Chemistry of Cyclopropanones". PATAI'S Chemistry of Functional Groups: Cyclopropyl Group. pp. 1455–1532. doi:10.1002/0470023449.ch23. ISBN9780470023440.
^Turro, Nicholas J. (1969). "Cyclopropanones". Accounts of Chemical Research. 2: 25–32. doi:10.1021/ar50013a004.
^Salaün, J.; Marguerite, J. (1985). "Cyclopropanone Ethyl Hemiacetal from Ethyl 3-Chloropropanoate". Organic Syntheses. 63: 147. doi:10.15227/orgsyn.063.0147.
^Salaun, Jacques (1983). "Cyclopropanone Hemiacetals". Chemical Reviews. 83 (6): 619–632. doi:10.1021/cr00058a002.
^Greene, Frederick D.; Sclove, David B.; Pazos, Jose F.; Camp, Ronald L. (1970). "Thermal reactions of a cyclopropanone. Racemization and decarbonylation of trans-2,3-di-tert-butylcyclopropanone". Journal of the American Chemical Society. 92 (25): 7488. doi:10.1021/ja00728a051.
^Moiseev, Andrey G.; Abe, Manabu; Danilov, Evgeny O.; Neckers, Douglas C. (2007). "First Direct Detection of 2,3-Dimethyl-2,3-diphenylcyclopropanone". The Journal of Organic Chemistry. 72 (8): 2777–2784. doi:10.1021/jo062259r. PMID17362038.
^Wiseman, Jeffrey S.; Abeles, Robert H. (May 2002). "Mechanism of inhibition of aldehyde dehydrogenase by cyclopropanone hydrate and the mushroom toxin coprine". Biochemistry. 18 (3): 427–435. doi:10.1021/bi00570a006. PMID369602.
