{{short description|Chemical compound}} {{chembox | Watchedfields = changed | verifiedrevid = 443700313 | ImageFile =Cyclopropanone.png | ImageSize =150px | PIN =Cyclopropanone |Section1={{Chembox Identifiers | ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} | ChemSpiderID = 122027 | InChI = 1/C3H4O/c4-3-1-2-3/h1-2H2 | InChIKey = VBBRYJMZLIYUJQ-UHFFFAOYAV | SMILES1 = O=C1CC1 | StdInChI_Ref = {{stdinchicite|correct|chemspider}} | StdInChI = 1S/C3H4O/c4-3-1-2-3/h1-2H2 | StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} | StdInChIKey = VBBRYJMZLIYUJQ-UHFFFAOYSA-N | CASNo_Ref = {{cascite|correct|??}} | CASNo =5009-27-8 | PubChem =138404 | SMILES =C1CC1=O }} |Section2={{Chembox Properties | C=3 | H=4 | O=1 | Appearance = Colorless | Density =0.867 g/mL at 25 °C | MeltingPtC = −90 | BoilingPtC = 50 to 53 | BoilingPt_notes = at 22 mmHg | Solubility = }} }}

'''Cyclopropanone''' is an organic compound with molecular formula (CH<sub>2</sub>)<sub>2</sub>CO 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.<ref name=Patai/>

==Preparation== Cyclopropanone has been prepared by reaction of ketene with diazomethane<ref name=Patai>{{cite book |doi=10.1002/0470023449.ch23|chapter=The Chemistry of Cyclopropanones|title=PATAI'S Chemistry of Functional Groups: Cyclopropyl Group|year=1987|last1=Wasserman|first1=Harry H.|last2=Berdahl|first2=Donald R.|last3=Lu|first3=Ta-Jung|pages=1455–1532|isbn=9780470023440}}</ref><ref>{{Cite journal | doi = 10.1021/ar50013a004| title = Cyclopropanones| journal = Accounts of Chemical Research| volume = 2| pages = 25–32| year = 1969| last1 = Turro| first1 = Nicholas J.}}</ref> in an unreactive solvent such as dichloromethane.<ref name=EROS>{{cite encyclopedia|doi=10.1002/047084289X.rc302|entry=Cyclopropanone|first=Norbert|last=De&nbsp;Kimpe|title=Cyclopropanone |encyclopedia=Encyclopedia of Reagents for Organic Synthesis |date=2001 |isbn=0-471-93623-5 }}</ref> These solutions are stable at −78&nbsp;°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:<ref>{{cite journal|first1=J. |last1=Salaün|first2=J.|last2=Marguerite|title=Cyclopropanone Ethyl Hemiacetal from Ethyl 3-Chloropropanoate|journal=Organic Syntheses|year=1985|volume=63|pages=147|doi=10.15227/orgsyn.063.0147}}</ref><ref>{{cite journal |doi=10.1021/cr00058a002|title=Cyclopropanone Hemiacetals|year=1983|last1=Salaun|first1=Jacques|journal=Chemical Reviews|volume=83|issue=6|pages=619–632}}</ref> :(CH<sub>2</sub>)<sub>2</sub>CO + X-H → (CH<sub>2</sub>)<sub>2</sub>C(X)(OH)&nbsp;&nbsp;&nbsp;&nbsp;(X-H = R<sub>2</sub>N-H, HO-H, RO-H) This reaction underlies cyclopropanone's polymerization at room temperature, initiated by traces of water.<ref name=Patai/>{{rp|1476}} The isocyanate adducts can also be prepared directly through photochemical rearrangement of succinimino ethers.<ref name=Patai/>{{rp|1462}}

==Structure== The C<sub>3</sub>O atoms are coplanar. As deduced from the microwave spectrum, the H<sub>2</sub>C-CH<sub>2</sub> 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.<ref name=Patai/>

The value of ν<sub>C=O</sub> in the infrared spectrum is near 1815&nbsp;cm<sup>−1</sup>, ca. 70&nbsp;cm<sup>−1</sup> 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.<ref name=Patai/>{{rp|pp=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).

:400px|Cyclopropanone tautomeric structures

Other reactions of cyclopropanones take place through this intermediate. For instance enantiopure (+)-''trans''-2,3-di-tert-butylcyclopropanone racemizes when heated to 80&nbsp;°C.<ref>{{Cite journal | doi = 10.1021/ja00728a051| title = Thermal reactions of a cyclopropanone. Racemization and decarbonylation of trans-2,3-di-tert-butylcyclopropanone| journal = Journal of the American Chemical Society| volume = 92| issue = 25| pages = 7488| year = 1970| last1 = Greene| first1 = Frederick D.| last2 = Sclove| first2 = David B.| last3 = Pazos| first3 = Jose F.| last4 = Camp| first4 = Ronald L.}}</ref>

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:<ref>{{Cite journal | doi = 10.1021/jo062259r| pmid = 17362038| title = First Direct Detection of 2,3-Dimethyl-2,3-diphenylcyclopropanone| journal = The Journal of Organic Chemistry| volume = 72| issue = 8| pages = 2777–2784| year = 2007| last1 = Moiseev| first1 = Andrey G.| last2 = Abe| first2 = Manabu| last3 = Danilov| first3 = Evgeny O.| last4 = Neckers| first4 = Douglas C.}}</ref>

:400px|2,3-Dimethyl-2,3-diphenylcyclopropanone intermediate in photolysis

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.<ref name=mechanism>{{cite journal |last1=Wiseman |first1=Jeffrey S. |last2=Abeles |first2=Robert H. |title=Mechanism of inhibition of aldehyde dehydrogenase by cyclopropanone hydrate and the mushroom toxin coprine |journal=Biochemistry |date=May 2002 |volume=18 |issue=3 |pages=427–435 |doi=10.1021/bi00570a006|pmid=369602}}</ref>

File:Coprine mechanism.png

==See also== * Other cyclic ketones: cyclobutanone, cyclopentanone, cyclohexanone * Other cyclopropane derivatives: cyclopropene, cyclopropenone

==References== {{reflist}}

3 Category:Cyclopropanes