Thermal reactions of 1,8-dimethylnaphthalene

The distribution of products from the thermal reaction of 1,8-dimethylnaphthalene in hydrous and anhydrous conditions at temperatures of 275-360°C has been shown to be controlled largely by the presence of brown coal, silica or clays during reaction. In particular, ratios of product 1,7- and 2,7-dimethylnaphthalene to parent 1,8-dimethylnaphthalene cannot be related to reaction temperatures. The role of water in the reaction is obscure. Certainly, conversion to the 1,7-isomer is promoted at 360°C, but otherwise, water inhibits the catalytic activity of clays and the generation of the 2,7-isomer. In addition, reflectance measurements (R) on a brown coal subjected to parallel thermal regimes, demonstrate R undergoes a greater increase in hydrous rather than anhydrous conditions. Geochemical interpretations of these data suggest that isometric distributions of the dimethylnaphthalenes may be more strongly influenced by sediment composition in terms of content of carbonaceous material, silica and clays than by temperature. In addition, these distributions may reflect concentrations of specific precursors and/or hydrocarbons synthesized in situ, rather than the thermal isomeric re-arrangements of existing hydrocarbons.