Structural Analysis of Reductively Methylated Coal Prepared in the Absence of Electron Transfer Agent. GC-MS Analysis of Hexane Soluble Portion

Yubari coal was reductively methylated in the absence of electron transfer agent (Miyake method, K/THF/CH3I) and the structure of hexane soluble portion (HS, 9.90%) was investigated in detail by GPC-LC separation followed by GC-MS, NMR and IR analyses. Typical reaction products consisted of reductive methylation products of na phthalene (6.9%in the HS), phenanthrene (0.7%), quinoline (0.2%) and naphthalene dimer (0.8%), and methyl ethers (1.2%) of reductive methylation products of naphthalene and phenanthrene. In addition, saturated compounds which were liberated from coal matrix collapsed were also contained. The saturated compounds consisted of biomarkers involving n-paraffins (5.20%in the HS), isoprenoid paraffins (0.9%), bicyclic monoterpenes (1.5%), tricyclic diterpenes (1.6 %) and pentacyclic triterpenes (1.4%). The reductive methylation products were compared with those obtained by the Sternberg method (K/THF/naphthalene/CH3I). It was found that the Sternberg-product was contaminated with the reductive dimerization products of naphthalene used as an electron transfer agent. Based on the structure of the reductive methylation products, solubilization mechanism of coal is discussed.