Carbene Proton Attachment Energies: Theoretical Study

Abstract

The geometries and electronic energies of six singlet carbenes, with methyl and phenyl substituents, and the corresponding carbenium ions were obtained using several density functional theory (DFT) variants and the second-order Møller-Plesset method for electron correlation and compared with G3 results, with the aim to determine a relatively low-cost computational protocol that is sufficiently accurate for the specific molecules and ions of interest. Some additional calculations were performed at the CCSD(T) level. Results for diphenylcarbene, methylphenylcarbene, and their cations, which were not previously investigated by ab initio methods, are reported as are calculations on methylene, methylcarbene, dimethylcarbene, and phenylcarbene. The MPW3LYP/6-311+G(d,p) hybrid DFT level was found to give results that were in close agreement with those obtained using G3 theory, with a mean absolute deviation (MAD) of 1.76 kcal/mol for the calculated proton attachment energies (PAEs). Equilibrium geometries obtained with this method were compared with those obtained at the MP2/6-311G(d,p) level of theory, and bond lengths and bond angles had MADs of 0.005 A and 1.0 degrees, respectively. Harmonic vibrational frequencies of all the carbene molecules and the corresponding ions were computed to verify that the stationary points were true minima, to obtain zero-point corrected energies, to assist in infrared studies of the molecules. The recommended combination of method and basis set is expected to be a useful framework that uses modest amounts of computer resources to obtain usable thermochemical data on moderate-sized hydrocarbons and hydrocarbon cations, including coal-mimetic species.

Mercury capture by native fly ash carbons in coal-fired power plants

“…The combination of HCl and NO 2 in the gas was a very effective promoter of Hg oxidation. The current thought is that multiple charges in the aromatic system avoids extensive delocalization and concentrates the charge and, thus, the oxidation potential at the protonated edge site [205-206]. …”

Density functional theory study on sensing properties of g‐C3N4 sheet to atmospheric gasses: Role of zigzag and armchair edges

“…In pure g-C 3 N 4 , the armchair edge carbons (carbyne type) and zigzag edge carbons (carbene type) serve as Lewis acidic and basic sites, respectively, where the former acts as an electrondeficient site and the latter as a nucleophile site for the target molecule. [38,39] To the best of our knowledge, no studies have been conducted to investigate the feasibility of zigzag and armchair g-C 3 N 4 structures as gas-sensing materials for detecting certain toxic gasses. In this study, the sensing abilities of the g-C 3 N 4 zigzag and armchair structures toward seven different ambient gasses (NO, NO 2 , CO, CO 2 , SO 2 , SO 3 , and O 2 ) are explored using density functional theory (DFT) calculations.…”

Comparação entre métodos compostos no cálculo de afinidades por próton e elétron em sistemas moleculares

“…15,16 Outras propriedades muito estudadas são as afinidades por próton [17][18][19][20][21][22][23] e por elétron, [24][25][26][27] a acidez, 28 bem como a identificação da estrutura mais estável para um determinado isômero. 29,30 Compostos inorgânicos também podem ser explorados utilizando métodos compostos pelo cálculo do potencial de redução 31 em reações de óxido-redução.…”