Theoretical Studies on Gas-Phase Reactions of Sulfuric Acid Catalyzed Hydrolysis of Formaldehyde and Formaldehyde with Sulfuric Acid and H₂SO₄···H₂O Complex

Abstract

The gas-phase reactions of sulfuric acid catalyzed hydrolysis of formaldehyde and formaldehyde with sulfuric acid and H2SO4···H2O complex are investigated employing the high-level quantum chemical calculations with M06-2X and CCSD(T) theoretical methods and the conventional transition state theory (CTST) with Eckart tunneling correction. The calculated results show that the energy barrier of hydrolysis of formaldehyde in gas phase is lowered to 6.09 kcal/mol from 38.04 kcal/mol, when the sulfuric acid is acted as a catalyst at the CCSD(T)/aug-cc-pv(T+d)z//M06-2X/6-311++G(3df,3pd) level of theory. Furthermore, the rate constant of the sulfuric acid catalyzed hydrolysis of formaldehyde combined with the concentrations of the species in the atmosphere demonstrates that the gas-phase hydrolysis of formaldehyde of sulfuric acid catalyst is feasible and could be of great importance for the sink of formaldehyde, which is in previously forbidden hydrolysis reaction. However, it is shown that the gas-phase reactions of formaldehyde with sulfuric acid and H2SO4···H2O complex lead to the formation of H2C(OH)OSO3H, which is of minor importance in the atmosphere.

Theoretical Studies on Reactions of OH with H2SO4…NH3Complex and NH2with H2SO4in the Presence of Water

“…The similar mechanism in the initial step of the NH 2 + H 2 SO 4 reaction has also been found in the NH 2 + HNO 3 reaction . The pre‐reactive C2 A complex is formed via double hydrogen bondings, which is similar to sulfuric acid monohydrate complex …”

“…The O−H … N hydrogen‐bonded distance in C2 A is calculated to be 1.675 Å, while the O … H−N is estimated to be 2.485 Å in Figure S4 (Supporting Information), which is in good agreement with the corresponding values reported in the literature . In Table , C2 A has a binding energy of ‐10.88 kcal/mol with respect to the separate reactants H 2 SO 4 and NH 2 , which is close to the binding energy of ‐10.70 kcal/mol in the H 2 SO 4 … H 2 O complex at the CCSD(T)/aug‐cc‐pv(T+d)z//M06‐2X/6‐311++G(3df,3pd) level . It is worth noting that the binding energy between sulfuric acid and amidogen radical is stronger than that of the HNO 3 … NH 2 complex by about 2.5 kcal/mol.…”

Effects of water, ammonia and formic acid on HO2 + Cl reactions under atmospheric conditions: competition between a stepwise route and one elementary step

“…The M06-2X functional is one of the best functionals with which to study noncovalent interactions 38,39 and has shown promising applications for estimating the thermochemistry and equilibrium structures for atmospheric reactions and molecular clusters. [40][41][42] At the M06-2X/6-311++G(2d,2p) level, the harmonic vibrational frequencies were calculated to verify the nature of the corresponding stationary points (minima or transition state) to provide the zero-point vibrational energy (ZPE) and to determine the thermodynamic contributions to the enthalpy and free energy. In addition, intrinsic reaction coordinate (IRC) [43][44][45] calculations were carried out to ensure that the transition states were connected to the desired reactants and products.…”

A theoretical study on the formation and oxidation mechanism of hydroxyalkylsulfonate in the atmospheric aqueous phase

“…M06-2X functional has been widely used in theoretical calculation and can be better for ionic hydrogen-bonding interactions and identifying the global minimum conformer. [29][30][31][32][33][34][35][36] Been considered as the "gold standard" of quantum chemistry, CCSD(T) method was widely been used for reactions of organic matters and has high level accuracy. Thus we choose M06-2X functional at the 6-311++G(d,p) basis set for geometrical structures optimization and CCSD(T) method with the aug-cc-pVTZ basis set for single point energy calculation in this paper.…”