A kinetic and product study of the 3-cyano-N-methyl-quinolinium photoinduced monoelectronic oxidation of a series of β-hydroxysulfoxides has been carried out to investigate the competition between Cα-S and Cα-Cβ bond cleavage within the corresponding cation radicals. Laser flash photolysis experiments unequivocally established the formation of sulfoxide cation radicals showing their absorption band (λmax ≈ 520 nm) and that of 3-CN-NMQ• (λmax ≈ 390 nm). Steady-state photolysis experiments suggest that, in contrast to what previously observed for alkyl phenyl sulfoxide cation radicals that exclusively undergo Cα-S bond cleavage, the presence of a β-hydroxy group makes, in some cases, the Cα-Cβ scission competitive. The factors governing this competition seem to depend on the relative stability of the fragments formed from the two bond scissions. Substitution of the β-OH group with -OMe did not dramatically change the reactivity pattern of the cation radicals thus suggesting that the observed favorable effect of the hydroxy group on the Cα-Cβ bond cleavage mainly resides on its capability to stabilize the carbocation formed upon this scission.

Competition between Cα-S and Cα-Cβ bond cleavage in β-Hydroxysulfoxides cation radicals generated by photoinduced electron transfer / Lapi, Andrea; D'Alfonso, Claudio; Del Giacco, Tiziana; Lanzalunga, Osvaldo. - In: PHOTOCHEMISTRY AND PHOTOBIOLOGY. - ISSN 0031-8655. - 97:(2021), pp. 1310-1321. [10.1111/php.13455]

Competition between Cα-S and Cα-Cβ bond cleavage in β-Hydroxysulfoxides cation radicals generated by photoinduced electron transfer

Lapi, Andrea
Writing – Original Draft Preparation
;
D'Alfonso, Claudio
Membro del Collaboration Group
;
Lanzalunga, Osvaldo
Conceptualization
2021

Abstract

A kinetic and product study of the 3-cyano-N-methyl-quinolinium photoinduced monoelectronic oxidation of a series of β-hydroxysulfoxides has been carried out to investigate the competition between Cα-S and Cα-Cβ bond cleavage within the corresponding cation radicals. Laser flash photolysis experiments unequivocally established the formation of sulfoxide cation radicals showing their absorption band (λmax ≈ 520 nm) and that of 3-CN-NMQ• (λmax ≈ 390 nm). Steady-state photolysis experiments suggest that, in contrast to what previously observed for alkyl phenyl sulfoxide cation radicals that exclusively undergo Cα-S bond cleavage, the presence of a β-hydroxy group makes, in some cases, the Cα-Cβ scission competitive. The factors governing this competition seem to depend on the relative stability of the fragments formed from the two bond scissions. Substitution of the β-OH group with -OMe did not dramatically change the reactivity pattern of the cation radicals thus suggesting that the observed favorable effect of the hydroxy group on the Cα-Cβ bond cleavage mainly resides on its capability to stabilize the carbocation formed upon this scission.
photoinduced electron transfer; sulfoxides; cation radical fragmentation
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Competition between Cα-S and Cα-Cβ bond cleavage in β-Hydroxysulfoxides cation radicals generated by photoinduced electron transfer / Lapi, Andrea; D'Alfonso, Claudio; Del Giacco, Tiziana; Lanzalunga, Osvaldo. - In: PHOTOCHEMISTRY AND PHOTOBIOLOGY. - ISSN 0031-8655. - 97:(2021), pp. 1310-1321. [10.1111/php.13455]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/1550644
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