a) Ozonation of isopropyl alcohol, isopropyl methyl ether, and cumenes produced the corresponding hydrotrioxides (ROOOH) and hydrogem trioxide (HOOOH), as identified by 1H, 13C, and 17O NMR spectroscopy. Studies of products and kinetics showed that the hydrotrioxides decompose in a radical process involving the homolytic cleavage of the RO-OOH bond, while water participates in the decomposition of HOOOH in a polar process to produce water and singlet oxygen (1O2) (Chemistry, 2000, 6, 809; J. Am. Chem. Soc. 2002, 124, 404). A theoretical study (DFT) revealed that the gas-phase ozonation of isopropyl alcohol is dominated by radical intermediates while the solution-phase mechanism is characterized by hydride transfer and the formation of the HOOO anion (J. Am. Chem. Soc. 2003, 125, 9395). In the gas-phase the singlet HOOO anion possesses a weak and long covalent HO-OO bond (1.8 A)(CCSD(T)), while in aqueous solution it adopts the geometry closely related to that of HOOOH, and can be regarded as the anion of this weak acid (J. Am. Chem. Soc. 2002, 124, 8462). Evidence for the HOOO anion was also obtained in the ozonation of 1,3-dioxolanes (J. Am. Chem. Soc. 2003, 125, 11260). Ozonation of norcarane yielded endo and exo norcarane hydrotrioxides. Further ozonation of the primary decomposition products of the ROOOH, i.e., 2-norcaranols, produced the corresponding hydrotrioxides and HOOOH (J. Org. Chem. 2003, 68, 9129). Experimental and theoretical studies of the ozonation of 1,2-diphelyhydrazine demostrated that HOOOH and 1,2-diphenyldiazene are the main reaction products. This is at present the method of choice for the preparation of HOOOH. The reaction involves HOOO radicals in the first step of the ozonation (J. Am. Chem. Soc. 2003, 125, 11553). b) Different 2-fluoro-2-halo-1,2-diphenylethanones (JOC 2000, 65, 6890-6896), 2-(3',5'-dimethoxyphenyl)-2-fluoro-1-phenylethanone, cyclic analogue 10,10-difluoro- phenanthren-9(10H)-one (Tetrahedron Lett. 2003, 44, 4247) and a model substrate of lignin; quinone methide were synthesised (Tetrahedron Lett. 2002, 43, 5669). Photolyses of those compounds in a various solvents resulted into complex reaction mixtures. The ratio between ionic and radical products depends on the nature and the position of a halogen atom bonded as well as the solvent used. In the first step the homolytic bond cleavage of either C-Cl, C-Br or C-O bond occurs. In the next step there is a competition between single electron transfer and diffusion of radicals from the solvent cage. The ability of solvent to donate a hydrogen atom is also important. Similar results were obtained in the photolysis of halosubstituted benzyl alcohols in the presence of semiconductive oxides (Chemosphere, 2000, 41, 1451-1455). (c) A new synthetic strategy for N-bromosaccharin (Synth. Commun. 1999, 29, 1779) was developed. (plus minus)-trans-7,8-Dihydroxy-6-fluoro-7,8-dihydrobenzo(a)pyrene (J. Org. Chem. 1999, 64, 1902) was synthesised and enantiomers were separated by chiral HPLC (J. Org. Chem. 2003, 68, 3291). Stabilities of carbocations in super acid media were studied. (Org. & Biomol. Chem. 2003, 1, 1509). Isomeric metabolites of benzo(a)pyrene were incorporated at guanines in single strands of sequence of human codons (Biochemistry 1999, 38, 569-581). DNA-adducts presented strong blocks but the DNA polymerase may bypass it (Mutat. Res. 2002, 508, 137). Mutations appear not only at sites where adducts are incorporated but also at distal positions (J. Biol. Chem. 2003, 278, 14940). (d) The abstraction of the iodine atom from ortho-substituted iodobenzenes with alkyl radicals was studied. The principal factors governing the energetics of the abstraction are steric strain and electronic interactions between iodine and the neighbouring substituent.