US EPA

2271263 

Journal Article 

Electron Transfer in Electrophilic Aromatic Nitration and Nitrosation: Computational Evidence for the Marcus Inverted Region 

Chen, Z; Mo, Y 

2013 

Yes 

Journal of Chemical Theory and Computation
ISSN: 1549-9618
EISSN: 1549-9626 

9 

10 

4428-4435 

26589160 

10.1021/ct400618k 

WOS:000326355100015 

Electrophilic aromatic nitrosation and nitration are among the most important electron transfer (ET) reactions. According to the electron transfer theory, an ET process can be described with two electron-localized diabatic states, and the electronic coupling between these two states, together with the organization energy and reaction energy, determine the ET efficiency. A proper definition of the strictly electron-localized states thus is the key. Here we used the valence bond theory to derive the diabatic states and probe the interactions of NO+ and NO2+ with benzene and identify the origin of their significant difference in reactivity. Results show that the high deformation cost for NO2+ overshadows the fact that it has much high charge transfer interaction in [C6H6,NO2](+). While NO+ uses pi orbitals to bind benzene and the orbital switch results in a high barrier from pi- to sigma-complex, NO2+ uses a vacant sigma(Nsp(2)) orbital, making the transition nearly barrierless. Significantly, we found that the post-ET state [C6H6+-NO] is more stable than the prior-ET state [C6H6,NO+]. Energy profiles with respect to the distance between the electrophile and the benzene confirm that the ET reaction of benzene and NO+ falls in the Marcus inverted region, and the outer-sphere ET occurs at similar to 2.6 angstrom with the electronic coupling energy of 1.06 eV, compared with the experimental estimate 1.4 +/- 0.5 eV.