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Effects of Strongly Perturbating Substituents on the Near UV Spectra of 3,4-Methylenedioxybenzene Derivatives

J. Vardin and B. Vidal

Laboratoire de Chimie Organique, Faculté des Sciences, Universitě de La Reunion, 97489 Saint-Denis Cédex, La Reunion (France D.O.M.)


Abstract: The 3,4-methylenedioxybenzene derivatives with strongly perturbating substituents (OH, NH2, NH3+, COCH3, CO2H, CHO, CN, NO2, etc.) display a charge-transfer nO, p --> πPh* transition towards λ  = 230-290 nm. The intensity of that transition is shown to depend on the electron density dO, p in nO, p orbital, the nonbonding pπ orbital of the oxygen of the fused membered ring being in para position to the substituent. It depends also on the value of the pi bond order BOCO, p  of the CPh-Op bond. As concerns the secondary transition, we have shown that the intensity arising from the π-donating effects of the para oxygen is quenched when substituent is strongly π-donor. Furthermore we explain why the intensity of the secondary transition (determined by εsec) roughly increases when the intensity of the charge-transfer transition (ε CT, O) increases.

Full paper in Portable Document Format: 465a301.pdf


Chemical Papers 46 (5) 301–314 (1992)

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