Radiation-Induced C -C Bond Cleavage in 1,2-Diarylethanes as Model Compounds of Coal, Part 3. Pulse and Steady-State Radiolysis of 1,2-Di(9-anthryl)ethane in Organic Solvents

1,2-Di(9-anthryl)ethane (1,2-DAE) was used as a model for coal to study the C -C bond cleavage of the ethano linkage in the radiolysis of solutions containing NaAlH2(OCH2CH2OCH3)2 [NaAlH2(OR)2]. Transient species were investigated by pulse radiolysis of solutions of 1,2-DAE in THF, DME and toluene in the absence and the presence of NaAlH2(OR)2. In the presence of NaAlH2(OR)2 stabilized, long-lived radical anion/sodium cation pairs of 1,2-DAE were generated even in the non-polar solvent toluene. The reaction mechanisms differ substantially for solutions in the ether solvents (THF or DME) and for solutions in toluene. Steady-state radiolysis (60Co γ-rays) of solutions of 1,2-DAE in toluene containing NaAlH2(OR)2 resulted in the C -C bond cleavage of the ethano linkage. This is attributed to the unstable dianion (1,2-DAE2-, 2Na+) formed in two successive radiation- induced reductions via (1,2-DAE∙- , Na+). The resulting (9-anthryl)methyl carbanionic fragments C14H9CH2-, Na+ react with AlH(OR)2 generated in the process, to form the aluminate salts [C14H9CH2AlH(OR)2-, Na+]. From the aluminate salts, 9-methylanthracene (9- MA) was obtained by hydrolysis in yields up to 65 wt.%.