EPR Study of the Thermal Decomposition of Transannular Peroxide of Anthracene

Lubomír Lapčík,Andrej Staško,Barbora Lapčíková

doi:10.4236/ijoc.2011.12007

Abstract

Thermal decomposition of transannular peroxide of anthracene (POA) (or 9,10-epidioxido anthracene) was studied by means of electron paramagnetic resonance spectroscopy (EPR) in the solid as well as in the liquid phases. Decomposition process proceeds via cleavage of the O-O bridge of the POA molecule, generating thus an alcoxy intermediate radical. Its concentration increases to a certain equilibrium stage during the time scale of the experiment. EPR spectra in the solid state were of the singlet type at the temperatures over 350 K, a doublet like anisotropic spectra were measured at the room temperature, both having g-value 2.0033. EPR spectrum from POA decomposed in benzene indicates four protons with higher (2aH = 0.305 mT, 2aH = 0.335 mT) and four protons with a lower (2aH = 0.075 mT, 2aH = 0.105 mT) splitting constants, corresponding well the radical expected after cleavage of O-O bridge.

Highlights

UV light irradiated anthracene and its derivatives in degassed solutions give anthracene dimers, while in the presence of oxygen they form endoperoxides [1,2]
electron paramagnetic resonance spectroscopy (EPR) spectra in the solid state were of the singlet type at the temperatures over 350 K, a doublet like anisotropic spectra were measured at the room temperature, both having g-value 2.0033
EPR spectrum from peroxide of anthracene (POA) decomposed in benzene indicates four protons with higher (2aH = 0.305 mT, 2aH = 0.335 mT) and four protons with a lower (2aH = 0.075 mT, 2aH = 0.105 mT) splitting constants, corresponding well the radical expected after cleavage of O-O bridge

Summary

Introduction

UV light irradiated anthracene and its derivatives in degassed solutions give anthracene dimers, while in the presence of oxygen they form endoperoxides [1,2]. As found by quantum chemical molecular orbital calculations based on Woodward-Hoffman orbital symmetry conservation principle application [3], endoperoxides of anthracene production is catalysed by transition metals atoms These thermally and photo chemically reactive substances (depending on the reaction conditions) are decomposed to the original hydrocarbon and simultaneously liberate singlet oxygen (1O2), or decompose by the disruption of the O-O bonds, producing highly reactive biradical, or by the transformation into the other types of peroxides [4]. The complex oxygen photosensitization in the presence of water soluble anthracene-1sulphonate was studied by means of EPR spin trapping method [10] It was found, that the anthracene-1-sulphonate in the presence of oxygen is converted to quinone and oxygen is activated to superoxide radical intermediate. In the paper presented thermal decomposition of transannular peroxide of anthracene (or anthracene 9,10endoperoxide, or 9,10-epidioxido-anthracene) is studied by means of electron paramagnetic resonance spectroscopy (EPR) both in the solid as well as in the liquid phase

Materials

Methods

Results and Discussion

Conclusions