An accurate DFT study within conformational survey of the D-form serine-alanine protected dipeptide.

The conformational analysis of N-formyl-D-serine-D-alanine-NH dipeptide was studied using density functional theory methods at B3LYP, B3LYP‒D3, and M06‒2X levels using 6‒311 + G (d,p) basis set in the gas and water phases. 87 conformers of 243 stable ones were located and the rest of them were migrated to the more stable geometries. Migration pattern suggests the more stable dipeptide model bears serine in β, γ, γ and the alanine in γ and γ configurations.

Atmospheric degradation mechanism of anthracene initiated by OH: A DFT prediction.

Density functional theory (DFT) calculations at the M06-2X/def2-TZVP level have been employed to investigate the atmospheric oxidation mechanism of anthracene (ANT) initiated by HO. Direct hydrogen atom abstraction from the ANT using HO takes place hardly at ambient conditions while addition of HO to the C1, C2, and C4 sites are thermodynamically and kinetically more advantageous. The addition reactions are controlled by the aromaticity and the kinetic trends were justified by resonance stabilization energies.

A comprehensive theoretical analysis of Curtius rearrangement of syn-syn and syn-anti conformers of oxalyl diazide.

The complete theoretical study of thermal Curtius rearrangement of syn-syn and syn-anti conformers of oxalyl diazide, in the gas phase and in solution has been established for the first time. The inexplicit solvent effect was taken into account via the self-consistent reaction field (SCRF) method. The gas and solution phases of all optimized geometries of the mentioned conformers associated with the Curtius rearrangement along the concerted and stepwise pathways were reported using the polarized continuum model and non-electrostatic terms from the SMD universal solvation model.

A reconnaissance DFT study of the full conformational analysis of N-formyl-L-serine-L-alanine-NH dipeptide.

Theoretical conformational analysis of N-formyl-L-serine-L-alanine-NH dipeptide model was investigated using B3LYP/6-311+G(d,p) and M06-2X/6-311+G(d,p) calculations. In this research, 243 total possible conformations of the dipeptide model were optimized including 87 stable conformers and the other disappeared ones migrated to more stable geometries. Migration pattern suggests more stability of the dipeptide model with the serine (ser) in β, γ, and γ and the alanine (ala) in γ and γ configurations, along with 26 of the found conformers having β-turn structures.

Investigation of simple and water assisted tautomerism in a derivative of 1,3,4-oxadiazole: a DFT study.

Investigation of tautomerism and transition states in a derivative of 1,3,4-oxadiazole (A, B, C and D) in the gas phase and in solution and in a micro hydrated environment with 1-3 water molecules was performed by calculations at the DFT-B3LYP/6-311++G(d,p) level of theory. The solvent effect is taken into account via the self-consistent reaction field (SCRF) method. The geometries of four possible tautomers of 5-amino-1,3,4-oxadiazole-2(3H)-one were optimized in the gas phase and solution with polarized continuum model (PCM).