A computational study on the spin-forbidden reaction mechanism and kinetics of naphthalene with NH radical

The reaction mechanism of naphthalene (C 10 H 8 ) and NH on both the triplet and singlet potential energy surfaces was investigated theoretically. Geometry optimizations for singlet state were performed at the B3LYP/cc-PVDZ level, while the energies of the optimized structures were refined using the M06-2X/aug-cc-pVTZ, CCSD(T)/aug-cc-pVDZ and MP2/aug-cc-pVTZ methods and corresponding method were applied for triplet states. This investigation reveals that the NH specie can add to various carbon atoms in the naphthalene molecule. On the singlet surface, products are formed by the addition of the 1 NH group to different carbon atoms in the aromatic ring of C 10 H 8 . A distinct class of products, observed for 1 P3 and 1 P5, involves the incorporation of the 1 NH group into a benzene ring of naphthalene, resulting in structures with more than six carbon atoms. On the triplet potential energy surface, both addition and cleavage products are accessible. Addition products are formed by the direct attachment of NH radicals to the aromatic ring, similar to the singlet pathway, while cleavage products result from the decomposition of related intermediates into two radical species. The most stable product on both the singlet and triplet surfaces is 1 P1. However, the calculated rate constant for the formation of 1 P5, 6.61 \(\:\times\:\) 10 + 17 cm 3 mol − 1 s − 1 , is higher than that of all other products. Furthermore, our calculations identified four primary minimum energy crossing points (MECPs), indicating that the overall reaction mechanism is more complex than a simple single-state pathway would suggest.