title: Polar Effects Control the Gas-phase Reactivity of Chargedpara-Benzyne Analogs.
abstract: The gas-phase reactivity of chargedpara-benzynes is entirely unexplored as they and/or their precursors tend to undergo ring-opening upon their generation. We report here a gas-phase reactivity study of two such benzynes, the 2,5-didehydropyridinium and 5,8-didehydroisoquinolinium cations, generated in a modified dual-linear quadrupole ion trap (DLQIT) mass spectrometer. Both biradicals were found to form diagnostic products with organic molecules, indicating the presence of two radical sites. As opposed to earlier predictions that the singlet-triplet (S-T) splitting controls the radical reactivity of such species, the 2,5-didehydropyridinium cation reacts much faster in spite of its larger S-T splitting. Calculated vertical electron affinities of the radical sites of thepara-benzynes, a parameter related to the polarity of the transition states of their reactions, appears to be the most important reactivity controlling factor.
authors.affiliation: Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, IN 47907 (USA).
authors.forename: Ashley M
authors.initials: AM
authors.lastname: Wittrig
authors.affiliation: Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, IN 47907 (USA).
authors.forename: Enada F
authors.initials: EF
authors.lastname: Archibold
authors.affiliation: Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, IN 47907 (USA).
authors.forename: Huaming
authors.initials: H
authors.lastname: Sheng
authors.affiliation: Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, IN 47907 (USA).
authors.forename: John J
authors.initials: JJ
authors.lastname: Nash
authors.affiliation: Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, IN 47907 (USA).
authors.forename: Hilkka I
authors.initials: HI
authors.lastname: Kenttämaa
keywords: Dual-linear quadrupole ion trap; Enediynes; Ion-molecule reactions; Mass spectrometry; Reactivity; para-Benzynes
references.citation: J Am Chem Soc. 2008 Dec 31;130(52):17697-709
references.pmid: 19061320
references.citation: Anal Chem. 2013 Dec 3;85(23):11284-90
references.pmid: 24171553
references.citation: Angew Chem Int Ed Engl. 2003 Feb 3;42(5):502-28
references.pmid: 12569480
references.citation: J Am Chem Soc. 2001 Oct 31;123(43):10691-8
references.pmid: 11674001
references.citation: Angew Chem Int Ed Engl. 2008;47(51):9860-5
references.pmid: 19006159
references.citation: Acta Pharm. 2007 Jun;57(2):133-50
references.pmid: 17507311
references.citation: J Phys Chem A. 2005 Nov 17;109(45):10348-56
references.pmid: 16833330
references.citation: Science. 2002 Aug 16;297(5584):1170-3
references.pmid: 12183628
references.citation: J Phys Org Chem. 2013 Sep;26(9):707-714
references.pmid: 34262240
references.citation: Chemistry. 2013 Jul 01;19(27):9022-33
references.pmid: 23703949