Structural Studies of Melanorrhoea usitate Lacquer Film Using Two‐stage Pyrolysis/Gas Chromatography/Mass Spectrometry

Abstract

Melanorrhoea usitate lacquer film was investigated using two-stage pyrolysis/gas chromatography/mass spectrometry. Monoenyl and saturated thitsiol components were detected by pyrolysis at 400 °C. The pyrolysis products of the thitsiol polymer, i.e. alkenes, alkanes, alkenylbenzenes, alkylbenzenes, alkenylphenols, alkylphenols and phenylalkylphenols were then detected together with the pyrolysis products of the glycoprotein and thitsiol components, by further pyrolysis at 500 °C. After studying their pyrolysis mechanisms, it was concluded that the lacquer film is terminated with monoenyl and saturated thitsiol components. Alkenes, alkanes, alkenyl- and alkylbenzenes are observed as thermally decomposed components from such terminal chains. Additionally, alkenes and alkanes having carbon chains longer than the side chains of 3-heptadecylcatechol, and alkenyl- and alkylbenzenes having carbon chains longer than C12 are detected as the pyrolysis products of thitsiol polymers formed by autoxidative side-chain/side-chain C—C coupling. Alkenyl-, alkyl- and phenylalkylphenols are the pyrolysis products of the C—O coupling polymer. These facts support the view that the polymerization of thitsiol proceeds through autoxidative side-chain/side-chain C—C coupling and nucleus/side-chain C—O coupling as well as by nucleus/side-chain C—C coupling.