I. Intermolecular Anti-Markovnikov Addition of Oxygen Nucleophiles to Alkenes: Direct and Indirect Catalytic Methods to Address a Fundamental Challenge Markovnikov versus anti-Markovnikov functionalization of alkenes is discussed, as well as the inherent challenge in overcoming Markovnikov selectivity. Stoichiometric and catalytic methods for anti-Markovnikov functionalization are discussed and appraised. II. Anti-Markovnikov Addition of Oxygen Nucleophiles to Alkene Cation Radical Intermediates The formation of alkene cation radicals is disccused, as well as examples of anti-Markovnikov nucleophilic addition to alkene cation radicals. III. The Direct Anti-Markovnikov Addition of Carboxylic Acids to Alkenes Using Photoredox Catalysis The conception and optimization of a photoredox catalysis system for the anti-Markovnikov addition of carboxylic acids to alkenes under visible light irradiation is described. IV. Investigations Into the Mechanism of the Polymerization of 4-Methoxystyrene Initiated by Pyrylium Salts Under Visible Light Irradiation Polymerization of 4-methoxystyrene using 2,4,6-tri(p-tolyl)pyrylium tetrafluoroborate as a photoinitiator is found to proceed via a cationic propagation mode. The effects of alcohol additives on the polymerization are discussed, and a proposal for the mechanism of their influence is put forward. Experiments to further elucidate the initiation and polymerization mechanism are proposed.