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Tropospheric Formation of Hydroxymethyl Hydroperoxide, Formic Acid, H 2 O 2 , and OH from Carbonyl Oxide in the Presence of Water Vapor: A Theoretical Study of the Reaction Mechanism
Author(s) -
Crehuet Ramon,
Anglada Josep M.,
Bofill Josep M.
Publication year - 2001
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20010518)7:10<2227::aid-chem2227>3.0.co;2-o
Subject(s) - chemistry , homolysis , radical , formic acid , decomposition , hydroxymethyl , bond cleavage , reaction mechanism , elementary reaction , photochemistry , yield (engineering) , catalysis , computational chemistry , inorganic chemistry , organic chemistry , kinetics , thermodynamics , physics , quantum mechanics
We have carried out a theoretical investigation of the gas‐phase reaction mechanism of the H 2 COO+H 2 O reaction, which is interesting for atmospheric purposes. The B3LYP method with the 6‐31G(d,p) and 6‐311+G(2d,2p) basis sets was employed for the geometry optimization of the stationary points. Additionally, single‐point CCSD(T)/6‐311+G(2d,2p) energy calculations have been done for the B3LYP/6‐311+G(2d,2p) optimized structures. The reaction begins with the formation of a hydrogen‐bond complex that we have calculated to be 6 kcal mol −1 more stable than the reactants. Then, the reaction follows two different channels. The first one leads to the formation of hydroxymethyl hydroperoxide (HMHP), for which we have calculated an activation barrier of Δ G a (298)=11.3 kcal mol −1 , while the second one gives HCO+OH+H 2 O, with a calculated activation barrier of Δ G a (298)=20.9 kcal mol −1 . This process corresponds to the water‐catalyzed decomposition of H 2 COO, and its unimolecular decomposition has been previously reported in the literature. Additionally, we have also investigated the HMHP decomposition. We have found two reaction modes that yield HCOOH+H 2 O; one reaction mode leads to H 2 CO+H 2 O 2 and a homolytic cleavage, which produces H 2 COOH+OH radicals. Furthermore, we have also investigated the water‐assisted HMHP decomposition, which produces a catalytic effect of about 14 kcal mol −1 in the process that leads to H 2 CO+H 2 O 2 .