Conformational analysis of hydrogen polyoxides

The semiempirical AM I method was used for the calculation of conformational potential energy surfaces of hydrogen trioxide and tetraoxide. The most stable conformation of trioxide is itsanti-form, which is characterized by the torsion angle = 82.3°, and that of tetraoxide is theanti, anti-form with = 80.7° (H-O-O-O) and 74.1° (O-O-O-O). The structures of the stable conformers are determined by the interaction between lone clectron pairs of oxygen atoms. The dipole-dipole interaction of OH groups is weaker than that in hydrogen peroxide. The results were used for the estimation of the polyoxide increment of the Benson's additivity scheme, _f H°[O-(O)₂] = 48±6 k1 mol^–1.Translated from lzveshyn Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1356-1361, June, 1996.     

Theoretical investigation of the structures and spectroscopic properties of (H2O4)n (n = 1–4) clusters

Density functional theory and ab initio calculations were performed to elucidate the hydrogen interactions in (H₂O₄)_n (n = 1–4) clusters. The optimized geometries, binding energies, and harmonic vibrational frequencies were predicted at various levels of theory. The trans conformer of the H₂O₄ monomer was predicted to be the most stable structure at the CCSD(T)/aug‐cc‐pVTZ level of theory. The binding energies per H₂O₄ monomer increased in absolute value by 9.0, 10.1, and 11.8 kcal/mol from n = 2 to n = 4 at the MP2/cc‐pVTZ level of theory (after the zero‐point vibrational energy and basis set superposition error corrections). This result implies that the intermolecular hydrogen bonds were stronger in the long‐chain clusters, that is, the formation of the longer chain in the (H₂O₄)_n clusters was more energetically favorable.     

Quantum-chemical calculations of O-O bond strengths in organic hydrotrioxides

The O-O bond strengths in ten organic hydrotrioxides have been calculated by semiempirical MNDO and AMI methods. The RO-OOH bond strength is independent of the nature of substituent R and is equal to 20.4±1.1 kcal mol^–1 (AM1). The influence of the inductive effect of substituent R on the value ofD(ROO-OH) has been established.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1129–1131, May, 1996.     

AM1 calculations of O-H bond dissociation energies in polyoxides

Energies of homolytic cleavage of O-H bonds in 33 compounds of the general formula Ro _n H (n = 2, 3, and 4) were calculated by the AMI method. For hydrotrioxides and hydrotetroxides, the bond dissociation energies are virtually independent of the nature of the substituent R:D(RO _n -H) = 92.3±0.8 kcal mol^–1 (n = 3 and 4).     

Theoretical characterization of hydrogen pentoxide,H2O5

Following our investigations on hydrogen polyoxides, herein we employed coupled cluster theory in conjunction with Dunning's correlation consistent basis sets and density functional theory to study HOOOOOH (H₂O₅). The infrared spectra of H₂O₅ and its three deuterated isotopologues, as well as those of the five single‐substituted ¹⁸O isotopologues are discussed in detail. Internal valence coordinates were employed to classify the vibrational modes. The Raman activity is reported to help in the identification of hydrogen pentoxide. The suggested enthalpy of formation is ΔH_f,298° (HOOOOH) = 1.4 ± 1.5 kcal/mol. This value includes corrections for relativistic and core‐valence effects as well as anharmonic corrections to Zero‐point energy corrections. © 2013 Wiley Periodicals, Inc.     

New trends along hydrogen polyoxides: unusually long oxygen–oxygen bonds in H2O6 and H2O7

By means of coupled cluster, G4 and B3LYP calculations, we characterised polyoxides H₂O₆ and H₂O₇. These two molecules behave very differently from lower polyoxides, given that some isomers present unusual bonding. In the case of H₂O₆, the central OO bond is predicted, to be 1.909 Å, at the CCSD(T)/cc-pVTZ level. Two conformational isomers of H₂O₆ display nearly the same enthalpy of formation, but only one of them has extremely long OO bonds. For H₂O₇, the most stable isomer also has two unusually long OO bonds. At the CCSD(T) level, and after extrapolation to the complete basis set limit, this isomer is predicted to be 5.37 kcal mol^–1 more stable than the one with short OO bonds, and the longest OO bond distance is expected to be close to 1.96 Å. Analysis of correlation energies indicated that the new isomers found for H₂O₆ and H₂O₇ are among the most strongly correlated molecules that can be formed with first-row atoms.     

Enthalpies of formation and O-O and C-O bond strengths in polyoxides RO x R′ and RO x

Bond strengths in RO-OOR, ROO-OH, and ROO-OOR (R, R = H, Me, Et, and Bu) molecules, calculated by the semiempirical quantum-chemical methods, were used to determine the enthalpies of formation of polyoxides RO _x R (x = 3, 4) and related radicals and the bond strengths (D/kcal mol^–1) in these molecules:D(ROOO-OR) = 33.2±0.9,D(ROOO-OH) = 37.5±0.7,D(R-O _x R) = 76.0±1.2,D(H-000) = 58.6,D(R-000) = 42.8±0.8. A new value of Benson's polyoxide thermochemical increment, _f H°[O-(O)₂] = 11.1±1.0 kcal mol^–1, was suggested.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2190–2193, September, 1996.