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Issue 5, 1998
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o-Quinone methide as a common intermediate in the pyrolysis of o-hydroxybenzyl alcohol, chroman and 1,4-benzodioxin

Abstract

The product composition in the very low pressure pyrolysis (550–1210 K) of o-hydroxybenzyl alcohol (HBA), 3,4-dihydro-2H-1-benzopyran (chroman), and 1,4-benzodioxin (BD) indicates that o-quinone methide (o-QM) is the common intermediate in each case. At complete conversion of HBA, o-QM was observed as the only product and the mass spectrum of o-QM could be obtained. At higher temperatures (>950 K), o-QM is subsequently converted into benzene and CO. The thermolysis process for chroman starts with cleavage of the phenoxy–carbon bond and proceeds with ethene elimination, yielding o-QM. The high pressure rate parameters for unimolecular decay have been determined to obey kchroman /s–1 = 1015.3 exp (–269/RT). For BD only the cleavage of the phenyl–vinoxy bond has been observed, and after rearrangement and CO elimination o-QM is formed. The Arrhenius equation for the overall rate of disappearance has been found as kBD /s–1 = 1015.6 exp (–310/RT). Ultimately (1100 K) the thermolysis of BD leads to 1 mole of benzene and 2 moles of CO.

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Article information


J. Chem. Soc., Perkin Trans. 2, 1998, 1173-1178
Article type
Paper

o-Quinone methide as a common intermediate in the pyrolysis of o-hydroxybenzyl alcohol, chroman and 1,4-benzodioxin

E. Dorrestijn, O. J. Epema, W. B. van Scheppingen and P. Mulder, J. Chem. Soc., Perkin Trans. 2, 1998, 1173
DOI: 10.1039/A800189H

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