Gas Chromatography Mass Spectrometry Identification of Labile Radicals Formed during Pyrolysis of Catechool, Hydroquinone, and Phenol through Neutral Pyrolysis Product Mass Analysis

Abstract

Catechol, hydroquinone, and phenol are known to be environmental pollutants due to their ability to generate environmentally free radicals, which cause millions of deaths worldwide. Recently, efforts have been done to precisely identify the origin and the nature of those free radicals employing EPR-LTMI technique. All the three precursors generate cyclopentadienyl radical as major pyrolysis products and phenoxyl radical as both pyrolysis and photolysis products which were obtained from phenol; ortho-semiquinone and para-semiquinone were seen, respectively, from the pyrolysis of catechol and hydroquinone. However, it has been suspected that the solely use of the EPR-LTMI did not allow the isolation of the more labile radicals that is supposedly terminated by radicalradical or radical-surface interaction. The present study reports the gas chromatography mass analysis of the pyrolysis products from catechol, hydroquinone, and phenol. Naphthalene , indene, and hydroxyindene were observed as the pyrolysis products of hydroquinone, while fluorene, 1H-indenol and its isomer 1H-inden-1-one 2,3 dihydro, acenaphthylene, benzofuran-7-methyl, and benzofuran-2-methyl were observed as pyrolysis products of catechol. Dibenzo dioxin and dibenzo furan were observed from pyrolysis of catechol and hydroquinone. Those products result from the combination of radicals such as cyclopentadienyl, parasemiquinone, ortho-semiquinone, hydroxyl-cyclohexadienyl, phenoxyl, and most importantly Hydroxycyclopentadienyl which was not identified by EPR-LTMI.

Post-Transition-State Direct Dynamics Simulations on the Ozonolysis of Catechol

“…The ozonolysis of aromatic hydrocarbons is unfavorable, but relatively fast ozonolysis of catechol has been observed from experiments . Catechol and other similar dihydroxybenzenes form due to pyrolysis, combustion, − and other anthropogenic activities like wood combustion and gasoline oxidation and are released directly into the atmosphere. It is the most common gas-phase organic constituent (∼50 ppbv).…”

Heterogeneous Oxidation of Catechol

“…6−8 Dihydroxybenzenes such as catechol are the most common gas-phase organic constituents (∼50 ppbv) resulting from biomass burning, 9 pyrolysis, and combustion. 10 Cloud water collected from brown clouds also contains aromatics such as catechol rings substituted with methyl, carbonyl, and nitro groups. 11 The surfactant properties of these species favor their accommodation at interfaces of aerosols, 12 where they are prone to undergo photooxidation.…”

“…The composition of WSOCs, atmospheric transport of biomass burning products, and photooxidation (e.g., of glyoxylic acid to generate oxalic acid) have been correlated at different sites. − Dihydroxybenzenes such as catechol are the most common gas-phase organic constituents (∼50 ppbv) resulting from biomass burning, pyrolysis, and combustion . Cloud water collected from brown clouds also contains aromatics such as catechol rings substituted with methyl, carbonyl, and nitro groups .…”

Effect of Temperature on the Molecular Weight Distribution in the Different Ranks of Coal during the On-Line Investigation of Coal Pyrolysis Gas Using Direct Photoionization Mass Spectroscopy

“…Benzene was practically the most varying compound in all the coal ranks at high temperatures, this can be attributed to concerted reactions which involve simultaneous rupturing (and forming) of more than one bond. Based on the explanation of the formation of CO at high temperatures, one typical reaction scheme involved si-multaneous reaction of hydrogen radical with cresols to form a seven-membered ring which later reacts with hydrogen radicals to form benzene and CO [32]. This may possibly be the reason benzene is the most dominant pyrolysis product compound in the SPI-TOFMS spectra at 800˚C, and why cresols (o-cresol) are the main phenolic compound at the othertemperatures.…”