The Naphthylcarbene Potential Energy Hypersurface

Abstract

The naphthylcarbene potential energy surface (PES) was examined ab initio, employing self-consistent field (SCF), second-order perturbation theory (MP2), and density functional (Becke3LYP) methods in conjunction with 6-31G*, DZ, DZP, and 6-311+G* basis sets. All stationary structures were characterized by vibrational frequency analyses at the Becke3LYP/6-31G* level; final energies were evaluated at the Becke3LYP/6-311+G*//Becke3LYP/6-31G* + ZPVE level. Cyclobuta[de]naphthalene is the global minimum on this part of the C11H8 PES. Generally, seven-membered benzocarbenes are no minima as they converge to their corresponding allenes. Both 1- and 2-naphthylcarbene have triplet ground states, but the small S−T gaps (ca. 5 kcal mol-1) allow facile rearrangements in the singlet manifold to take place. The triplet rotational barrier for the exo-methylene in 2-naphthylcarbene is relatively small (3.5 kcal mol-1) due to weak π-bonding. At low temperatures, singlet 2-naphthylcarbene equilibrates with 2,3-benzobicyclo[4.1.0]hepta-2,4,6-triene and bicycloheptatetra-1,3,5,7-ene, but not with 4,5-benzocycloheptatrienylidene which is not a minimum; rearrangement to singlet 1-naphthylcarbene occurs only at higher temperatures via bicycloheptatetra-1,2,4,6-ene, the second lowest minimum. As the rearrangement barriers from 1- and 2-naphthylcarbene to bicycloheptatetra-1,2,4,6-ene are of similar magnitude (ΔΔE ⧧ = 1.9 kcal mol-1), the latter species may be observed in small quantities only. The allenes bicycloheptatetra-1,2,4,6-ene, bicycloheptatetra-1,3,5,7-ene, and bicycloheptatetra-2,3,5,7-ene are thermodynamically remarkably stable and should be observable at low temperatures.

Graft copolymerization of glycidylmethacrylate onto modified nylon‐6 fibers

“…Based on the MAD (mean average deviation) values with reference to experimental quantities, it was concluded that B3LYP is clearly superior to MP2 and other density functionals 40–44. Moreover, for carbenes, B3LYP gives a better description of the singlet state 45–53. We therefore expect the B3LYP calculations to be more reliable.…”

Time‐dependent density functional theory study on hydrogen‐bonded intramolecular charge‐transfer excited state of 4‐dimethylamino‐benzonitrile in methanol

“…The infrared intensities were determined from the gradients of the dipole moment 71–73. All the calculated vibrational frequencies are scaled by a factor of 0.95 to correct the anharmonicity effects in this work 69–76. All the electronic structure calculations were carried out using the TURBOMOLE program suite 66–70…”

Matrix isolation and photochemistry of 1- and 2-naphthylchlorocarbene

“…Flash vacuum pyrolysis of either the 1-or 2-diazomethylnaphthalenes gave this isomer as a major product. Xie et al, 24 have also found that the cyclobutanaphthalene lies ca. 28 kcal mol Ϫ1 below the benzobicycloheptatriene 6 at the B3LYP/6-311ϩG* level, and that this isomer represents the global minimum on the C 11 H 8 energy surface.…”