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RESEARCH PRODUCT
Unexpectedly ambivalent O-2 role in the autocatalytic photooxidation of 2-methoxybenzyl alcohol in water
Vincenzo AugugliaroVittorio LoddoAndrea PaceGabriele ScanduraBilge Sina TekSedat YurdakalLeonardo PalmisanoGiovanni Palmisanosubject
chemistry.chemical_classificationSettore ING-IND/24 - Principi Di Ingegneria ChimicaAqueous solutionAutocatalytic photooxidation 2-Methoxybenzyl alcohol 2-Methoxybenzaldehyd O2 quenchingHomogeneous photocatalysisProcess Chemistry and Technologychemistry.chemical_elementAlcoholSettore CHIM/06 - Chimica OrganicaPhotochemistryOxygenAldehydeCatalysisCatalysisAutocatalysischemistry.chemical_compoundchemistrySettore CHIM/03 - Chimica Generale E InorganicaAlcohol oxidationPhysical and Theoretical ChemistryAbsorption (chemistry)description
An unusual autocatalytic photooxidation of 2-methoxybenzyl alcohol has been observed under UV irradiation in aqueous medium. The homogeneous oxidation is catalyzed by the corresponding aldehyde that is also the main oxidation product. The trend of alcohol disappearance rate matches the typical shape of an autocatalytic process, where a crucial and ambivalent role is played by the presence of molecular oxygen. Low oxygen concentrations give rise to a zero-order reaction since the beginning of irradiation, while higher amounts of oxygen reduce the alcohol oxidation rate until the aldehyde reaches a concentration high enough to speed up the alcohol's conversion. Experiments performed by varying alcohol, aldehyde and oxygen concentrations in both aqueous and organic media suggest that the alcohol oxidation is initially favored by the presence of oxygen. Once the formed aldehyde competes for photon absorption, the oxidation is driven by aldehydes alpha cleavage leading to reactive oxygenated species in aqueous medium. An excess of oxygen quenches the latter processes thus inhibiting/slowing down the reaction. (C) 2015 Elsevier B.V. All rights reserved. tAn unusual autocatalytic photooxidation of 2-methoxybenzyl alcohol has been observed under UV irradi-ation in aqueous medium. The homogeneous oxidation is catalyzed by the corresponding aldehyde that isalso the main oxidation product. The trend of alcohol disappearance rate matches the typical shape of anautocatalytic process, where a crucial and ambivalent role is played by the presence of molecular oxygen.Low oxygen concentrations give rise to a zero-order reaction since the beginning of irradiation, whilehigher amounts of oxygen reduce the alcohol oxidation rate until the aldehyde reaches a concentrationhigh enough to speed up the alcohol’s conversion. Experiments performed by varying alcohol, aldehydeand oxygen concentrations in both aqueous and organic media suggest that the alcohol oxidation is ini-tially favored by the presence of oxygen. Once the formed aldehyde competes for photon absorption,the oxidation is driven by aldehydes alpha cleavage leading to reactive oxygenated species in aqueousmedium. An excess of oxygen quenches the latter processes thus inhibiting/slowing down the reaction.
| year | journal | country | edition | language |
|---|---|---|---|---|
| 2015-07-01 |