Structure, reactivity and vibrational spectra of formohydroxamic and silaformohydroxamic acids: a comparative ab initio study

Density functional study of the intramolecular proton transfer and conformations in hydroxyaminosilanethione

“…Natural bond orbital analysis was then performed using the NBO 3.1 program [11] included in GAUSSIAN 03 package of programs at B3LYP/6-311++G(d,p) level of theory. Using this approach the orbital interactions can be quantitatively described in terms of the second-order perturbation interaction energy (E (2) ) [12,13]. The charge density generated at the B3LYP/6-311++G(d,p) level of theory has been analyzed using the quantum theory atoms in molecules (QTAIM) developed by Bader [14].…”

“…Natural atomic hybrid (NHOs) and the polarization coefficients of the molecules are given in Table 4. Important second order delocalization energies E (2) that are representative of the extent of electron delocalization are given in Table 5. According to the simple bond orbital picture, an NBO is defined as an orbital formed from natural atomic orbitals.…”

“…Like their hydroxamic acid analogous, thiohydroxamic acids may exist in two tautomeric forms, thione (1) or thiol (2). Despite their wide applications, very little is known about the structures of substituted thiohydroxamic acids and few computational studies have been reported.…”

“…The stabilization energies associated with the dimerization of thioformohydroxamic acid and formohydroxamic acid tautomers and their relationship to proton affinities and deprotonation enthalpies have also been considered [1]. The structure and the gas-phase acidities of formohydroxamic acid and silaformohydroxamic acid derivatives have been examined, and it appears that sila-substitution produces an appreciable shift in the harmonic vibration frequencies of the formohydroxamic acid [2]. Only a small number of theoretical calculations have been carried out on the hydroxyaminosilanethione, the earliest of these showing that the substitution of the central carbon atom by silicon significantly influences the structure and acidity in comparison to the parent molecule [2].…”

“…The structure and the gas-phase acidities of formohydroxamic acid and silaformohydroxamic acid derivatives have been examined, and it appears that sila-substitution produces an appreciable shift in the harmonic vibration frequencies of the formohydroxamic acid [2]. Only a small number of theoretical calculations have been carried out on the hydroxyaminosilanethione, the earliest of these showing that the substitution of the central carbon atom by silicon significantly influences the structure and acidity in comparison to the parent molecule [2]. The molecular structure of hydroxyphosphinecarbothialdehyde has also been studied in the gas phase and the interconversion of its tautomers via intramolecular hydrogen transfer has been investigated by density functional theory [3].…”