Visible-Light-Driven Toluene Oxidation to Benzaldehyde over WO₃ Nanostructures

Photochemical and Oxidative Degradation of Chamazulene Contained in Artemisia, Matricaria and Achillea Essential Oils and Setup of Protection Strategies

“…Another photodegradation product, CA carbaldehyde, is most probably formed from the reaction of molecular oxygen with a chamazulene (carbon-centered) radical to give rise to a peroxyl radical intermediate (ROO•, Scheme 1 ), which subsequently affords a further sidechain oxidation, forming the aldehyde derivative of chamazulene. This manner of reaction is similar to the well-accepted mechanism of autooxidation of the sidechain in alkylbenzenes and alkylnaphthalenes [ 29 , 33 , 34 ]. The peroxyl radical is quite stable, yet highly reactive toward unsaturated lipids: when formed in a cosmetic product or other man-directed preparations, it can trigger the oxidation of other ingredients, causing the formation of toxic byproducts [ 16 ] and the formulation to lose its stability and change its properties.…”

“…Another photodegradation product, CA carbaldehyde, is most probably formed from the reaction of molecular oxygen with a chamazulene (carbon-centered) radical to give rise to a peroxyl radical intermediate (ROO•, Scheme 1), which subsequently affords a further sidechain oxidation, forming the aldehyde derivative of chamazulene. This manner of reaction is similar to the well-accepted mechanism of autooxidation of the sidechain in alkylbenzenes and alkylnaphthalenes [29,33,34]. The peroxyl radical is quite Another photodegradation product, CA carbaldehyde, is most probably formed from the reaction of molecular oxygen with a chamazulene (carbon-centered) radical to give rise to a peroxyl radical intermediate (ROO•, Scheme 1), which subsequently affords a further sidechain oxidation, forming the aldehyde derivative of chamazulene.…”

“…Another photodegradation product, CA carbaldehyde, is most probably formed from the reaction of molecular oxygen with a chamazulene (carbon-centered) radical to give rise to a peroxyl radical intermediate (ROO•, Scheme 1), which subsequently affords a further sidechain oxidation, forming the aldehyde derivative of chamazulene. This manner of reaction is similar to the well-accepted mechanism of autooxidation of the sidechain in alkylbenzenes and alkylnaphthalenes [29,33,34]. The peroxyl radical is quite proton transfer (ET-PT sequence) or a concerted PCET (proton-coupled-electron-transfer) to O2 [31,32] would afford the hydroperoxyl radical HOO• (the neutral form of superoxide) and the C-centered radical of CA, which can decay by disproportionation.…”

“…These are conceivably to be attributed to the presence of the isopropyl group in guaiazulene. This enables the formation of a relatively stable benzyl-type tertiary alkyl radical in guaiazulene, which, in the presence of oxygen, would form a relatively persistent tertiary alkylperoxyl radical, having a different fate and reactivity compared to the primary or secondary alkyl/alkylperoxyl radicals attainable in CA [ 33 , 34 ].…”

Photochemical and Oxidative Degradation of Chamazulene Contained in Artemisia, Matricaria and Achillea Essential Oils and Setup of Protection Strategies

“…Another photodegradation product, CA carbaldehyde, is most probably formed from the reaction of molecular oxygen with a chamazulene (carbon-centered) radical to give rise to a peroxyl radical intermediate (ROO•, Scheme 1), which subsequently affords a sidechain oxidation, forming the aldehyde derivative of chamazulene. This manner of reaction is similar to the well accepted mechanism of autooxidation of the sidechain in alkylbenzenes and alkylnaphthalenes [23,27,28]. The peroxyl radical is quite stable, yet highly reactive toward unsaturated lipids: when formed in a cosmetic product or other man-directed preparations, it can trigger the oxidation of other ingredients, causing the formation of toxic byproducts [16], and the formulation to lose its stability and change its properties.…”