SOLVOLYSIS OF EXO-2-BICYCLO[3.2.0]HEPT-6-ENYL AND ENDO-2-BICYCLO[3.2.0]HEPT-6-ENYL TOSYLATES AND CORRESPONDING 1,4,4-TRIMETHYL DERIVATIVES AND 4,4,6-TRIMETHYL DERIVATIVES - STERIC AND CONFORMATIONAL EFFECTS ON RING ENLARGEMENTS OF RESULTING CARBOCATIONS