The pyrolysis of polycarbonyl compounds. III. Pyrolysis and mass spectrometry of 1,1,4,4-Tetramethyltetralin-2,3-dione and related compounds

The pyrolysis of 1,1,4,4-tetramethyltetralin-2,3-dione (I) or of 1,1,3,3-tetra-methylindan-2-one (11) at 800°/0.01-0.2 mm with short contact time gave a hydrocarbon pyrolysate containing naphthalene (c.60%), accompanied by smaller amounts of indene, 2- and 3-methylindenes, 1,2-dihydronaphthalene, benzofulvene, 1- and 2-methylnaphthalenes, dimethylnaphthalenes, and several unidentified minor components. Pyrolysates of similar composition were obtained from o-isopropyl-a-methylstyrene (111), 1,1,3-trimethylindane (IV), and 1,l-dimethyl-indene (V). Benzofulvene (VI) was partly converted into naphthalene at 800º. The last four compounds are suggested as possible intermediates in the conversion of (I) and (11) into naphthalene. The pyrolytic behaviour of these compounds correlates well with their 70-eV mass spectra; this apparent correlation is a more complex case than has previously been reported.