X-RAY CRYSTALLOGRAPHIC STRUCTURE DETERMINATION AND CARBON-13 NUCLEAR MAGNETIC RESONANCE SPECTRUM OF 2,2,3,4,5,6,6-HEPTACHLORO-3-(2,3,4,5,6-PENTACHLOROPHENOXY)-4-CYCLOHEXENONE. AN INTERMEDIATE IN THE SYNTHESIS OF NONACHLORO-3-PHENOXYPH