UV Photochemistry of Peroxyformic Acid (HC(O)OOH): An Experimental and Computational Study Investigating 355 nm Photolysis

Abstract

The photochemistry of peroxyformic acid (PFA), a molecule of atmospheric interest exhibiting internal hydrogen bonding, is examined by exciting the molecule at 355 nm and detecting the nascent OH fragments using laser-induced fluorescence. The OH radicals are found to be formed in their ground electronic state with the vast majority of available energy appearing in fragment translation. The OH fragments are vibrationally cold (v" = 0) with only modest rotational excitation. The average rotational energy is determined to be 0.35 kcal/mol. Further, the degree of OH rotational excitation from PFA is found to be significantly less than that arising from the dissociation of H2O2 as well as other hydroperoxides over the same wavelength. Ab initio calculation at the EOM-CCSD level is used to investigate the first few electronic excited states of PFA. Differences in the computed torsional potential between PFA and H2O2 help rationalize the observed variation in their respective OH fragment rotational excitation. The calculations also establish that the electronic excited state of PFA accessed in the near UV is of (1)A" symmetry and involves a σ*(O-O) ← n(O) excitation. Additionally, the UV absorption cross section of PFA at 355 and 282 nm is estimated by comparing the yield of OH from PFA at these wavelengths to that from hydrogen peroxide for which the absorption cross sections is known.

A Systematic Theoretical Study on the Stability of a Series of Dialkyl Peroxides to Light and Heat

“…One can see SI Table S3 that the vertical excitation energies of singlet and triplet are compared to those obtained with EOM‐CCSD//MP2 theoretical level by Indulkar et al. and with MS‐CASPT2//CASPT2/gas by Song et al., respectively . The results in this work are similar to the results of the previous studies, and the small differences between this work and those studies can be attributed to the different level of theory employed in the calculations.…”

“…Firstly, the optimized ground‐state geometry parameters and peroxide bond energy of H 2 O 2 calculated with four basis sets including cc‐PVDZ, aug‐cc‐PVDZ, cc‐PVTZ, and aug‐cc‐PVTZ are listed in Table , and they are compared with the previous studies . One can see that the bond length obtained with the aug‐cc‐PVTZ basis set is closer to the experimental value, however, the optimized dihedral angle is quite different from experiment.…”

Atmospheric Chemistry of Enols: The Formation Mechanisms of Formic and Peroxyformic Acids in Ozonolysis of Vinyl Alcohol

“…This may have implications for the missing source of FA in the atmospheric models, where currently it is a challenge to model the effective FA production from VA ozonolysis due to lack of kinetic data for the other atmospheric transformations of VA. Furthermore, it can be seen that the ozonolysis of VA provides a new source of PA in the atmosphere, which is an important species in the troposphere due to its potential for generating the OH radicals as well as its contribution to the formation of SOA . The “hot” PA formed in ozonolysis of VA may promptly decompose to HCOO and OH radicals, because its internal energy is sufficiently high due to the energy released from VA + O 3 to PA + HCHO.…”

“…Furthermore, it can be seen that the ozonolysis of VA provides a new source of PA in the atmosphere, which is an important species in the troposphere due to its potential for generating the OH radicals as well as its contribution to the formation of SOA. 58 The "hot" PA formed in ozonolysis of VA may promptly decompose to HCOO and OH radicals, because its internal energy is sufficiently high due to the energy released from VA + O 3 to PA + HCHO. Meanwhile, the produced CH 2 OO and anti-HOCHOO with high internal energy could either be stabilized to sCI by collision or isomerize promptly.…”