Benchmark calculations of proton affinity and gas‐phase basicity using multilevel (G4 and G3B3), B3LYP and MP2 computational methods of para‐substituted benzaldehyde compounds

Abstract

This study presents the benchmark calculations of proton affinities (PAs) and gas-phase basicities (GBs) of 8-para substituted benzaldehyde compounds using the multilevel model chemistries (G3B3 and G4), density-functional quantum model (B3LYP) and ab initio model (MP2). The results show that the computed properties are strongly correlated with the available experimental data. The PAs and the GBs of other eight para-substituted benzaldehyde compounds, for which the experimental data does not currently exist, have been calculated using G3B3 and B3LYP methods.

Substitution effect on the adiabatic ionization potential, vertical ionization potential, electrophilicity, and nucleophilicity of some hydantoin drug derivatives: Computational study

“…Therefore, the selection of this moderate level of theory can be rationalized based on the successful of the B3LYP in many applications including geometric structures. 9,21,[80][81][82][83][84] The 12 AIP values (with corrected ZPE) of the hydantoin derivatives are reported in Table S4. In order to check the validity and accuracy of the examined 16 DFT methods, the statistical analysis using some important statistical descriptors, including mean unsigned deviation (MD), mean average deviation (MAD), mean square error (MSE), root mean square error (RMSE), and determination coefficient (R 2 ) with respect to the standard reference values (Table S5), was carried out, and the results are summarized in Table 2.…”

“…The analysis of the fundamental gaps' results of the different hydantoin derivatives (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12) shows that the values of this parameter vary from 9.43 to 10.93 eV. The data in Table 3 indicate that substitution of EDGs (Me, NH 2 , and OH) decreases the energy gap of the substituted hydantoin derivatives and consequently increases the chemical reactivity.…”

“…The dipole moment is the first derivative of the energy with respect to an applied electric field as a measure of asymmetry in the molecular charge distribution. 28 The dipole moment of hydantoin and its derivatives (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12) in the gas phase are also reported in Table 2. It is found that 5-dimethylaminohydantoin (7), with EDG (NMe 2 ) substitution at C5, has the largest dipole moment, and the 5-carbaldehydehydantoin (9), with EWG substitution of CHO at C5, has the smallest dipole moment.…”

“…High-level ab initio and density functional theory (DFT) methods were successfully used to calculate the intrinsic properties of the organic molecules such as proton affinity, gas-phase basicity, vertical ionization potential, and adiabatic electron affinity with reasonable accuracy and in excellent agreement with the experimental data. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] Influence of exchange-correlation potentials and basis sets on the ionization potentials and electron affinities computations of nucleic acids bases were also explored using B3PW91 and B3LYP methods with different basis sets. 13,14 Interestingly, the results obtained using DFT methods 15,16,21 were well compared with those obtained by using highlevel ab initio methods.…”

Gas phase H+, H3O+ and NH4+ affinities of oxygen-bearing volatile organic compounds; DFT calculations for soft chemical ionisation mass spectrometry

“…34,35 Several studies were recently carried out in an attempt to predict PA of organic molecules using ab initio or DFT computational approaches. [36][37][38] Additionally, PA was calculated for indole 39 as a benchmark using ab initio MP2 (Moller-Plesset with second-order energy correction) and DFT with two functionals B3LYP and M06-2X and five different basis sets to compare their agreement with available experimental values revealing that B3LYP is optimal in terms of computational cost and accuracy, even with a relatively restricted basis set 6-31+G(d,p). PA and IE were then calculated for several classes of molecules using this level of theory.…”