Wittrig Ashley M, Archibold Enada F, Sheng Huaming, Nash John J, Kenttämaa Hilkka I
Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, IN 47907 (USA).
Int J Mass Spectrom. 2015 Feb 1;377:39-43. doi: 10.1016/j.ijms.2014.04.017.
The gas-phase reactivity of charged -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 the -benzynes, a parameter related to the polarity of the transition states of their reactions, appears to be the most important reactivity controlling factor.
带电荷的苯炔的气相反应性完全未被探索，因为它们和/或其前体在生成时往往会发生开环反应。我们在此报告了在改进的双线性四极杆离子阱（DLQIT）质谱仪中生成的两种此类苯炔，即2,5-二脱氢吡啶鎓和5,8-二脱氢异喹啉鎓阳离子的气相反应性研究。发现这两种双自由基均与有机分子形成诊断产物，表明存在两个自由基位点。与早期预测的单重态-三重态（S-T）分裂控制此类物种的自由基反应性相反，2,5-二脱氢吡啶鎓阳离子尽管具有较大的S-T分裂，但反应速度要快得多。计算得出的苯炔自由基位点的垂直电子亲和力，这是一个与其反应过渡态极性相关的参数，似乎是最重要的反应性控制因素。
