TY - JOUR
T1 - On the factors that control the reactivity of meta-benzynes
AU - Gao, Jinshan
AU - Jankiewicz, Bartłomiej J.
AU - Reece, Jennifer
AU - Sheng, Huaming
AU - Cramer, Christopher J.
AU - Nash, John J.
AU - Kenttämaa, Hilkka I.
PY - 2014/6
Y1 - 2014/6
N2 - The reactivities of eleven 3,5-didehydropyridinium and six 2,4-didehydropyridinium cations toward cyclohexane were examined in the gas phase by using Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometry as well as high-level quantum chemical calculations. The results unequivocally demonstrate that the reactivity of meta-benzyne analogs can be "tuned" from more radical-like to less radical-like by changing the type and position of substituents. For example, σ-acceptor substituents at the 4-position and π-donor substituents at the 2-position in 3,5-didehydropyridinium cations partially decouple the biradical electrons, which results in lower energy transition states, and faster radical reactions. In contrast, σ-acceptors at the 2-position and π-donors at the 4-position in 3,5-didehydropyridinium cations cause stronger coupling between the biradical electrons, which results in lower radical reactivity. Three main factors are found to control the reactivity of these biradicals: (1) the energy required to distort the minimum energy dehydrocarbon atom separation to the separation of the transition state, (2) the S-T splitting at the separation of the transition state, and (3) the electron affinity at the separation of the transition state. This journal is
AB - The reactivities of eleven 3,5-didehydropyridinium and six 2,4-didehydropyridinium cations toward cyclohexane were examined in the gas phase by using Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometry as well as high-level quantum chemical calculations. The results unequivocally demonstrate that the reactivity of meta-benzyne analogs can be "tuned" from more radical-like to less radical-like by changing the type and position of substituents. For example, σ-acceptor substituents at the 4-position and π-donor substituents at the 2-position in 3,5-didehydropyridinium cations partially decouple the biradical electrons, which results in lower energy transition states, and faster radical reactions. In contrast, σ-acceptors at the 2-position and π-donors at the 4-position in 3,5-didehydropyridinium cations cause stronger coupling between the biradical electrons, which results in lower radical reactivity. Three main factors are found to control the reactivity of these biradicals: (1) the energy required to distort the minimum energy dehydrocarbon atom separation to the separation of the transition state, (2) the S-T splitting at the separation of the transition state, and (3) the electron affinity at the separation of the transition state. This journal is
UR - http://www.scopus.com/inward/record.url?scp=84900296801&partnerID=8YFLogxK
U2 - 10.1039/c4sc00194j
DO - 10.1039/c4sc00194j
M3 - Article
AN - SCOPUS:84900296801
SN - 2041-6520
VL - 5
SP - 2205
EP - 2215
JO - Chemical Science
JF - Chemical Science
IS - 6
ER -