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An evaluation of the application of a TiO 2 / Cu(II)/solar simulated radiation system for selective oxidation of benzyl alcohol derivatives
Author(s) -
Marotta Raffaele,
Di Somma Ilaria,
Spasiano Danilo,
Andreozzi Roberto,
Caprio Vincenzo
Publication year - 2013
Publication title -
journal of chemical technology and biotechnology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.64
H-Index - 117
eISSN - 1097-4660
pISSN - 0268-2575
DOI - 10.1002/jctb.3914
Subject(s) - benzyl alcohol , chemistry , alcohol , selectivity , alcohol oxidation , benzoic acid , photocatalysis , nitro , substrate (aquarium) , benzaldehyde , organic chemistry , photochemistry , catalysis , medicinal chemistry , alkyl , oceanography , geology
BACKGROUND: The conversion of hydroxybenzyl alcohols, nitro‐benzyl alcohol and methoxybenzyl alcohols into the corresponding aldehydes is attempted in aqueous solution by Cu(II) (which reduces to Cu(0)), at room temperature, under acidic and deaerated conditions, using TiO 2 solar simulated light photocatalysis. RESULTS: Under the experimental conditions adopted, the yields of the corresponding hydroxyaldehydes, when Cu(II) was completely reduced to Cu(0), were 21.6% for 4‐hydroxybenzaldehyde, 11.5% for 3‐hydroxybenzaldehyde and 20.2% for 2‐hydroxybenzaldehyde. Higher conversions of 2‐methoxybenzyl alcohol and 4‐methoxybenzyl alcohol were recorded relative to unsubstituted benzyl alcohol. A selectivity of 5.2%, at 50% conversion of the substrate, was observed for the oxidation of 4‐nitrobenzyl alcohol to 4‐nitrobenzaldehyde. For high degrees of aromatic alcohols conversion, oxidation of the generated aldehydes to the corresponding benzoic acid derivatives is observed. CONCLUSION: The introduction of substituents into the aromatic alcohols structure changes the photocatalytic oxidation rate and product selectivities with respect to that previously observed for unsubstituted benzyl alcohol. In particular, the presence of both electron donating (hydroxy, methoxy groups) and electron withdrawing (nitrogroup) groups on the aromatic ring of the substrate causes a detrimental effect on the selectivity of the process with respect to the case of benzyl alcohol. © 2012 Society of Chemical Industry