%0 Generic
%A Adeuya, Anthony
%A Price, Jason M.
%A Jankiewicz, Bartłomiej J.
%A Nash, John J.
%A Kenttämaa, Hilkka I.
%D 2009
%T Gas-Phase Reactivity of Protonated 2-, 3-, and 4-Dehydropyridine Radicals Toward Organic Reagents
%U https://acs.figshare.com/articles/dataset/Gas_Phase_Reactivity_of_Protonated_2_3_and_4_Dehydropyridine_Radicals_Toward_Organic_Reagents/2807047
%R 10.1021/jp901380y.s016
%2 https://acs.figshare.com/ndownloader/files/4501579
%K Charged radicals 2
%K electrophilic carbon atom
%K phenyl radicals
%K HCN
%K resonance
%K CN
%K tetrahydrofuran yields products
%K hydrogen atom
%K iodine atom abstraction
%K reactivity
%K hydrogen atom abstraction
%X To explore the effects of the electronic nature of charged phenyl radicals on their reactivity, reactions of the three distonic isomers of n-dehydropyridinium cation (n = 2, 3, or 4) have been investigated in the gas phase by using Fourier-transform ion cyclotron resonance mass spectrometry. All three isomers react with cyclohexane, methanol, ethanol, and 1-pentanol exclusively via hydrogen atom abstraction and with allyl iodide mainly via iodine atom abstraction, with a reaction efficiency ordering of 2 > 3 > 4. The observed reactivity ordering correlates well with the calculated vertical electron affinities of the charged radicals (i.e., the higher the vertical electron affinity, the faster the reaction). Charged radicals 2 and 3 also react with tetrahydrofuran exclusively via hydrogen atom abstraction, but the reaction of 4 with tetrahydrofuran yields products arising from nonradical reactivity. The unusual reactivity of 4 is likely to result from the contribution of an ionized carbene-type resonance structure that facilitates nucleophilic addition to the most electrophilic carbon atom (C-4) in this charged radical. The influence of such a resonance structure on the reactivity of 2 is not obvious, and this may be due to stabilizing hydrogen-bonding interactions in the transition states for this molecule. Charged radicals 2 and 3 abstract a hydrogen atom from the substituent in both phenol and toluene, but 4 abstracts a hydrogen atom from the phenyl ring, a reaction that is unprecedented for phenyl radicals. Charged radical 4 reacts with tert-butyl isocyanide mainly by hydrogen cyanide (HCN) abstraction, whereas CN abstraction is the principal reaction for 2 and 3. The different reactivity observed for 4 (as compared to 2 and 3) is likely to result from different charge and spin distributions of the reaction intermediates for these charged radicals.
%I ACS Publications