title: Studies of cyclization reactions of linear cumulenes and heterocumulenes using the neutralization-reionization procedure and/or ab initio calculations.
abstract: A number of linear cumulenes and heterocumulenes have been made by charge stripping of anions of known bond connectivity in the source of a mass spectrometer. Some of these reactive molecules have been identified in interstellar molecular clouds. The structures of these neutrals may be investigated by reionization to a decomposing positive ion [the neutralization-reionization technique ((-)NR(+))], and/or by ab initio calculations. Energized linear cumulenes and heterocumulenes may undergo cyclization to form stable cyclic isomers. To cite a selection of the examples described in this review: (i) four-atom systems CCCC and some heterocumulenes CCCX (X=B, N, Al, Si, P) involve the formation of stable four-membered ring rhombic (also called kite and fan) structures. One of the cyclic molecules, cyclo-C(3) Si, has been detected in interstellar molecular clouds, (ii) five-atom cumulene and heterocumulene systems are more complex. Linear CCCCC rearranges the carbon skeleton by forming a C substituted rhomboid system, CCCCO forms a three-membered cyclic isomer, while nitrogen containing five-atom cumulenes effect nitrile to isonitrile interconversion via three-centered cyclized intermediates, and (iii) CCCCCC and CCCCBO cyclize to give unique six-membered ring systems.
authors.affiliation: Department of Chemistry, The University of Adelaide, South Australia, Australia.
authors.forename: Tianfang
authors.initials: T
authors.lastname: Wang
authors.forename: John H
authors.initials: JH
authors.lastname: Bowie
mesh_terms: D055580:Astronomical Phenomena; D002244:Carbon / Q000737:chemistry; D003500:Cyclization; D005118:Extraterrestrial Environment; D007477:Ions / Q000737:chemistry*; D007536:Isomerism; D013058:Mass Spectrometry / Q000295:instrumentation*; D008958:Models, Molecular; D015394:Molecular Structure; D011090:Polyenes / Q000737:chemistry*
chemical_list: D007477:Ions; D011090:Polyenes; D002244:Carbon