Abstract
In this work, we report the gas phase UV absorption spectra and the kinetics of the OH-oxidation of 1H-1,2,3-triazole and pyrazole. UV spectra were determined between 200 and 250 nm, at 350 ± 2 K and at pressures between 0.09 and 0.3 Torr. The reported maximal UV absorption cross sections are (cm2 per molecule): σ206 nm, 1H–1H-1,2,3-triazole = 2.04 × 10−18 and σ203 nm, pyrazole = 5.44 × 10−18. The very low absorption capacity of these compounds beyond 240 nm indicates that their atmospheric photodissociation is negligible. The OH-oxidation of these species was performed in an atmospheric simulation chamber coupled to an FTIR spectrometer and to a GC/MS over the temperature range 298–357 K and at atmospheric pressure. Experiments were conducted in relative mode using benzaldehyde, trans-2-hexenal and heptane as references. The obtained rate constants at 298 K were (×10−11 cm3 per molecule per s): k(OH + 1H-1,2,3-triazole) = 2.16 ± 0.41; k(OH + pyrazole) = 2.94 ± 0.42. These results were compared to those available in the literature and discussed in terms of structure-reactivity and temperature dependency. Their tropospheric lifetimes with respect to reaction with OH radicals were then estimated.
Highlights
Five-membered nitrogen heterocycles with a triazole or pyrazole moiety play an important role in organic chemistry: they are present in many organic species including natural, medicinal, and agricultural products.[1,2,3]
The Comprehensive Medicinal Chemistry (CMC) database lists more than 67% of compounds contain heterocyclic rings as pesticides as well as antiviral and antibacterial agents.[4,5,6,7]
The results showed that the reaction is preferably carried out by adding the OH radical to the pyrrole ring (C4H5N)
Summary
Five-membered nitrogen heterocycles with a triazole or pyrazole moiety play an important role in organic chemistry: they are present in many organic species including natural, medicinal, and agricultural products.[1,2,3] Most of pharmaceuticals are products that mimic natural products with biological activity and are heterocyclic compounds with a triazole or/and pyrazole ring systems. The Comprehensive Medicinal Chemistry (CMC) database lists more than 67% of compounds contain heterocyclic rings as pesticides (insecticides, fungicides) as well as antiviral and antibacterial agents.[4,5,6,7] these compounds are used as in several industrial applications such as in polymers,[8] corrosion inhibitors,[3,9] ligands for transition metals,[10,11] cosmetic colorings,[2,8,12] solvents, antioxidants and UV stabilizers.[8,12,13] the usage of such nitrogen heterocycles species leads to their release into the atmosphere. Atmospheric measurements conducted by Jakob et al and Teich et al.[14,15] detected the presence of ve-membered
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