Spin‐Spin Coupling Controls the Gas‐Phase Reactivity of Aromatic σ‐Type Triradicals

Abstract

Examination of the reactions of σ-type quinoliniumbased triradicals with cyclohexane in the gas phase demonstrated that the radical site that is the least strongly coupled to the other two radical sites reacts first, independent of the intrinsic reactivity of this radical site, in contrast to related biradicals that first react at the most electron-deficient radical site. Abstraction of one or two H atoms and formation of an ion that formally corresponds to a combination of the ion and cyclohexane accompanied by elimination of a H atom ("addition-H") were observed. In all cases except one, the most reactive radical site of the triradicals is intrinsically less reactive than the other two radical sites. The product complex of the first H atom abstraction either dissociates to give the H-atom-abstraction product and the cyclohexyl radical or the more reactive radical site in the produced biradical abstracts a H atom from the cyclohexyl radical. The monoradical product sometimes adds to cyclohexene followed by elimination of a H atom, generating the "addition-H" products. Similar reaction efficiencies were measured for three of the triradicals as for relevant monoradicals. Surprisingly, the remaining three triradicals (all containing a meta-pyridyne moiety) reacted substantially faster than the relevant monoradicals. This is likely due to the exothermic generation of a meta-pyridyne analog that has enough energy to attain the dehydrocarbon atom separation common for H-atom-abstraction transition states of protonated meta-pyridynes.

A Portable Reagent Inlet System Designed to Diminish the Impact of Air and Water to Ion–Molecule Reactions Studied in a Linear Quadrupole Ion Trap

“…In addition to the reactions of the 4-hydroxyphenylcarbyne anion with acetonitrile, reactions of several other ions with various reagents were explored (Table , see Figures S2–S8). These systems were selected because the mass spectra obtained previously by using the traditional manifold revealed abundant, unexpected, and undesirable H 2 O adducts. , As observed for the 4-hydroxyphenylcarbyne anion/acetonitrile system discussed above, the relative abundance of H 2 O adducts of the reacting ions were found to be substantially lower for all the reactions studied when using the portable system than when using the traditional manifold. Based on these results, the portable system introduced 10–60% of the H 2 O into the ion trap that was introduced using the traditional manifold.…”

“…This reagent was synthesized using procedures described in the literature . 2-Iodo-5-nitroquinoline, 2-iodo-6-nitroquinoline, 4,6-diiodoquinoline, and 5-nitro-8-iodoquinoline were used to generate 2,5-didehydroquinolinium cation, 2,6-didehydroquinolinium cation, 4,6-didehydroquinolinium cation, and 5,8-didehydroquinolinium cation, respectively, in the mass spectrometer . These precursors were synthesized as described previously. ,, …”

“…23 2-Iodo-5-nitroquinoline, 2-iodo-6-nitroquinoline, 4,6-diiodoquinoline, and 5-nitro-8-iodoquinoline were used to generate 2,5-didehydroquinolinium cation, 2,6-didehydroquinolinium cation, 4,6-didehydroquinolinium cation, and 5,8-didehydroquinolinium cation, respectively, in the mass spectrometer. 24 These precursors were synthesized as described previously. 19,24,25 The reagents for ion−molecule reactions were all purchased from Sigma-Aldrich and are as follows: acetonitrile (purity 99.8%), allyl iodide (purity 98%), and cyclohexane (purity 99.5%).…”

“…24 These precursors were synthesized as described previously. 19,24,25 The reagents for ion−molecule reactions were all purchased from Sigma-Aldrich and are as follows: acetonitrile (purity 99.8%), allyl iodide (purity 98%), and cyclohexane (purity 99.5%).…”

Spin‐Spin Coupling between the Biradical Moieties in Aromatic Tetraradicals Increases their Reactivity

“…The radicals 2 – 12 have been reported previously [10,11] . The tetraiodo‐precursor of tetraradical 1 was synthesized as shown in Scheme 1 [12] .…”