Abstract
Oxidation of alcohols plays an important role in industrial chemistry. Novel green techniques, such as sonochemistry, could be economically interesting by improving industrial synthesis yield. In this paper, we studied the selective oxidation of benzyl alcohol as a model of aromatic alcohol compound under various experimental parameters such as substrate concentration, oxidant nature and concentration, catalyst nature and concentration, temperature, pH, reaction duration, and ultrasound frequency. The influence of each parameter was studied with and without ultrasound to identify the individual sonochemical effect on the transformation. Our main finding was an increase in the yield and selectivity for benzaldehyde under ultrasonic conditions. Hydrogen peroxide and iron sulfate were used as green oxidant and catalyst. Coupled with ultrasound, these conditions increased the benzaldehyde yield by +45% compared to silent conditions. Investigation concerning the transformation mechanism revealed the involvement of radical species.
Highlights
In industrial chemistry, selective oxidation is commonplace as it enables the synthesis of carbonyl compounds, alcohols, epoxides, carboxylic acids, ethers, and esters [1] that are used in various fields, such as agroindustry, pharmaceuticals, cosmetics, and dyes
We investigated the influence of catalyst amount on the transformation yield of benzyl alcohol to benzaldehyde (Figure 3)
We investigated simple and environmentally sustainable reaction conditions to selective oxidize benzyl alcohol into benzaldehyde
Summary
Selective oxidation is commonplace as it enables the synthesis of carbonyl compounds, alcohols, epoxides, carboxylic acids, ethers, and esters [1] that are used in various fields, such as agroindustry, pharmaceuticals, cosmetics, and dyes. Some processes developed in laboratories are not suitable for industrial applications due to safety concerns, like thermal hazards and hazardous waste production [1,2,3] For these reasons, sustainable activation techniques that would enable the use of abundant, cheap, and safe reagents must be developed. 2 O2 may decompose during the reaction with the targeted substrate, performed experiments in thethe oxidant was not molar we performed experiments which in which oxidant was notintroduced introducedall allatatonce. 2O2 (3.72 mmol) was divided into two portions, of 1.86 mmol each, that were introduced amount of H2 O2 (3.72 mmol) was divided into two portions, of 1.86 mmol each, that were introduced at 0 min and = 7.5For min For both introduction modes (all atportioned), once and portioned), similar tat= t0 =min and at t =at 7.5t min
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