RADIATION-INDUCED C-C BOND-CLEAVAGE IN 1,2-DIARYLETHANES AS MODEL COMPOUNDS OF COAL .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 (Co-60 gamma-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-DAE(2-), 2 Na+) 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.%.