Janez Cerkovnik

Dihydrogen trioxide clusters, (HOOOH)n (n = 2−4) and the hydrogen-bonded complexes of HOOOH with acetone and dimethyl ether: implications for the decomposition of HOOOH

Hydrogen-bonded gas-phase molecular clusters of dihydrogen trioxide (HOOOH) have been investigated using DFT (B3LYP/6-311++G(3df,3pd)) and MP2/6-311++G(3df,3pd) methods. The binding energies, vibrational frequencies, and dipole moments for the various dimer, trimer, and tetramer structures, in which HOOOH acts as a proton donor as well as an acceptor, are reported. The stronger binding interaction in the HOOOH dimer, as compared to that in the analogous cyclic structure of the HOOH dimer, indicates that dihydrogen trioxide is a stronger acid than hydrogen peroxide. A new decomposition pathway for HOOOH was explored. Decomposition occurs via an eight-membered ring transition state for the intermolecular (slightly asynchronous) transfer of two protons between the HOOOH molecules, which form a cyclic dimer, to produce water and singlet oxygen (Delta (1)O 2). This autocatalytic decomposition appears to explain a relatively fast decomposition (Delta H a(298K) = 19.9 kcal/mol, B3LYP/6-311+G(d,p)) of HOOOH in nonpolar (inert) solvents, which might even compete with the water-assisted decomposition of this simplest of polyoxides (Delta H a(298K) = 18.8 kcal/mol for (H 2O) 2-assisted decomposition) in more polar solvents. The formation of relatively strongly hydrogen-bonded complexes between HOOOH and organic oxygen bases, HOOOH-B (B = acetone and dimethyl ether), strongly retards the decomposition in these bases as solvents, most likely by preventing such a proton transfer.

An efficient methyltrioxorhenium(VII)-catalyzed transformation of hydrotrioxides (ROOOH) into dihydrogen trioxide (HOOOH).

Dihydrogen trioxide (HOOOH) is formed nearly quantitatively in the low-temperature (-70 degrees C) methyltrioxorhenium(VII) (MTO)-catalyzed transformation of silyl hydrotrioxides (R3SiOOOH), and some acetal hydrotrioxides, in various solvents, as confirmed by 1H, and 17O NMR spectroscopy. The calculated energetics (B3LYP) for the catalytic cycle, using H3SiOOOH as a model system, is consistent with the experimentally observed activation energy (9.5 +/- 2.0 kcal/mol) and a small kinetic solvent isotope effect (kH2O/kD2O = 1.1 +/- 0.1), indicating an initial concerted reaction between the silyl hydrotrioxide and MTO in the rate-determining step. With the addition of water in the next step, the intermediate undergoes a sigma-bond metathesis reaction to break the Re-OOOH bond and form HOOOH, together with the second dihydroxy intermediate. The final step in the catalytic cycle involves a second, catalytic water that lowers the barrier to form H3SiOH and MTO.

The search for protonated dihydrogen trioxide (HOOOH): insights from theory and experiment.

Protonated dihydrogen trioxide (HOOOH) has been postulated in various forms for many years. Protonation can occur at either the terminal (HOOO(H)H(+)) or central (HOOH(OH)(+)) oxygen atom. However, to date there has been no definitive evidence provided for either of these species. In the current work we have employed ab initio methods, CCSD(T) and MP2, with a large basis set (6-311++G(3df,3pd)) to determine the relative stabilities of these species. It is shown that the terminally protonated species is strongly favored relative to the centrally protonated species (DeltaE = 15.8 kcal/mol, CCSD(T)//MP2). The mechanism of formation of HOOO(H)H(+) was determined to occur with a low barrier with the H(3)O(+) occurring in a thermoneutral reaction (DeltaE = -0.3 kcal/mol, CCSD(T)//MP2). Although HOOO(H)H(+) exists as a stable intermediate, it is extremely short-lived and rapidly decomposes (DeltaE* = 8.6 kcal/mol, MP2) to H(3)O(+) and O(2)((1)Delta(g)). The decomposition reaction is stabilized by solvent water molecules. The short-lived nature of the intermediate implies that the intermediate species can not be observed in (17)O NMR spectra, which has been demonstrated experimentally.

A Simple and Efficient Preparation of High‐Purity Hydrogen Trioxide (HOOOH)

A simple and efficient method allows the synthesis of solutions of high-purity hydrogen trioxide (HOOOH), released in the low-temperature methytrioxorhenium(VII) (MTO)-catalyzed transformation of the ozonized polystyrene-supported dimethylphenylsilane. High-purity hydrogen trioxide solutions in diethyl ether, separated from the polymer and free of any reactants and by-products, can be stored at -20 °C for weeks. By removing the solvent in vacuo, HOOOH could be isolated in highly pure form or transferred to other solvents, thus significantly extending the research perspectives of HOOOH for novel applications.