Quadratic complete basis set ab initio and hybrid density functional theory studies of the stability of HNC, HCN, H2NCH and HNCH2, their isomerizations, and the hydrogen insertion reactions for HCN and HNC

1997 ◽  
Vol 93 (14) ◽  
pp. 2355-2359 ◽  
Author(s):  
Branko S. Jursic
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Basis Set ◽  
Hybrid Density Functional Theory ◽  
Insertion Reactions ◽  
Functional Theory ◽  
Complete Basis Set ◽  
The Stability ◽  
Hybrid Density Functional ◽  
Hydrogen Insertion

Complete basis set, hybrid-density functional theory study, and natural bond orbital interpretations of the conformational behavior of halocarbonyl, thiocarbonyl, and selenocarbonyl isocyanates

2012 ◽  
Vol 90 (4) ◽  
pp. 333-343 ◽  
Author(s):  
Seiedeh Negar Mousavi ◽  
Davood Nori-Shargh ◽  
Hooriye Yahyaei ◽  
Kobra Mazrae Frahani
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Energy Difference ◽  
Basis Set ◽  
Hybrid Density Functional Theory ◽  
Total Dipole Moment ◽  
Functional Theory ◽  
Complete Basis Set ◽  
Conformation Stability ◽  
Hybrid Density Functional

Complete basis set CBS-QB3, hybrid-density functional theory (B3LYP/Def2-TZVPP) based methods and NBO interpretation were used to investigate the impacts of the stereoelectronic effects and electrostatic and steric interactions on the conformational properties of halocarbonyl isocyanates (halo = F (1), Cl (2), and Br (3)), halothiocarbonyl isocyanates (halo = F (4), Cl (5), and Br (6)), and haloselenocarbonyl isocyanates(halo = F (7), Cl (8), and Br (9)). Both methods showed that the Z-conformations of compounds 1, 4, and 7 are more stable than their corresponding E conformations, but the stability of the E conformations, when compared with the corresponding Z conformations, increases from compound 1 to compound 3, compound 4 to compound 6, and also from compound 7 to compound 9. The NBO analysis showed that the generalized anomeric effect (GAE) is in favor of the Z conformations of compounds 1, 4, and 7. The GAE values calculated (i.e., GAEE–GAEZ) increase from compound 1 to compound 3, compound 4 to compound 6, and also from compound 7 to compound 9. On the other hand, there are none of the same trends between the calculated total dipole moment and the Gibbs free energy difference values between the E and Z conformations (i.e., ΔμE–Z and ΔGE–Z) of compounds 1–3, 4–6, and 7–9. Accordingly, the GAE succeeds in accounting for the increase of the E conformation stability from compound 1 to compound 3, compound 4 to compound 6, and also from compound 7 to compound 9. Therefore, the GAE associated with the electron delocalization, not the total dipole moment changes (i.e., ΔμE–Z), is a reasonable indicator of the total energy difference in compounds 1–3, 4–6, and 7–9. There is a direct correlation between the calculated GAE and Δ[r2–6(E) – r2–6(Z)] parameters. Importantly, there are interesting through-space electron delocalizations (LP2X6→π*C4–O5) that justify the increase of the E conformation stability from compound 1 to compound 3, compound 4 to compound 6, and also from compound 7 to compound 9, when compared with their corresponding Z conformations. The correlations between the GAE, bond orders, total steric exchange energies (TSEE), ΔGZ–E, ΔμE–Z, structural parameters, and conformational behaviors of compounds 1–9 were investigated.

Sign in / Sign up

Export Citation Format

Share Document