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Effect of Substituents on Partial Photocatalytic Oxidation of Aromatic Alcohols Assisted by Polymeric C 3 N 4
Author(s) -
Krivtsov Igor,
Ilkaeva Marina,
GarcíaLópez Elisa I.,
Marcì Giuseppe,
Palmisano Leonardo,
Bartashevich Ekaterina,
Grigoreva Ekaterina,
Matveeva Ksenia,
Díaz Eva,
Ordóñez Salvador
Publication year - 2019
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201900362
Subject(s) - benzaldehyde , reactivity (psychology) , chemistry , benzyl alcohol , selectivity , electrophile , aldehyde , photocatalysis , alcohol , photochemistry , medicinal chemistry , organic chemistry , catalysis , medicine , alternative medicine , pathology
In the present work we scrutinize the effect of substituents in the phenyl ring of the benzyl alcohol on its photo‐oxidation to the corresponding benzaldehyde driven by polymeric carbon nitride photocatalyst in aqueous medium. It has been established that electron donating (ED) substituents in para‐ and ortho‐ position with respect to the CH 2 OH‐group promote the reactivity of the substrate without compromising the selectivity towards benzaldehyde formation, maintaining it in the range of 84–98 %, if compared to the unsubstituted molecule. The same observation is true for meta‐ substituted benzyl alcohol with an electron withdrawing (EW) group. On the other hand, the presence of ED‐group in meta‐ position or EW‐group in para‐ position with respect to the CH 2 OH‐group reduces the reactivity as well as the selectivity towards the aldehyde production, resulting in the values of selectivity ranging from 40 to 80 %. Quantum chemical calculations have allowed to establish that the reactivity correlates with the positive charge on the benzylic carbon in benzyl alcohol cation intermediate, while the selectivity, most probably, is conditioned by a negative charge on the carbon atoms in the phenyl ring being a target for an electrophile attack. The modification of the polymeric C 3 N 4 photocatalyst with H 2 O 2 reduces the unselective benzyl alcohol oxidation, thus favouring the higher selectivity towards benzaldehyde production.