MECHANOCHEMICAL REACTION OF DDT WITH CALCIUM-OXIDE

Evidence is presented that, in the mechanochemical destruction of DDT [2,2-bis(4-chlorophenyl)-1,1,1-trichloroethane] by ball milling in the presence of calcium oxide, a complex series of reactions occurs along the pathway to a product that appears to be essentially graphitic, th ough aromatic chloro and hydroxy substituents are retained to some deg ree. The production of the various intermediates can be understood in terms of processes initiated at both CaO and steel (of the milling dev ice) surfaces. With the exception of DDE [2,2-bis(4-chlorophenyl)-1,1- dichloroethene], most of these intermediates attain maximum concentrat ions corresponding to < 1 mol % of the original DDT and have been char acterized only by their mass spectra. In the case of dichlorotolane [b is(4-chlorophenyl)ethyne], however, yields are sufficient for it td be isolated chromatographically as a pure, crystalline solid and charact erized further by NMR spectroscopy. After 12 h of milling, no organic materials volatile enough to be detected by conventional GC/MS procedu res are present, but the black, graphitic residue does retain some chl orine that is only slowly removed by extended milling.