This thesis is in two distinct parts. Part I describes an investigation of the oxidative coupling of ethynyl compounds, and the syntheses of certain cyclic conjugated alpha-diynes. Part II describes the investigation of the addition of dinitrogen tetroxide to long-chain unsaturated acids. Part I is subdivided into three sections. Section I describes the preliminary investigation of the oxidative coupling reaction of ethynyl compounds, and its successful extension to reaction in homogeneous organic medium. Section II describes the use of a high-dilution modification of the conditions to provide the first cyclic poly-ynes, the properties and reactions of which are discussed. Section III discusses the possible syntheses of novel conjugated macrocycles by the oxidative coupling reaction, and describes one such macrocycle, from o-diethynylbenzene, and an investigation of its properties and reactions. Part II describes an investigation of the addition products of the addition of dinitrogen tetroxide to long-chain unsaturated acids, in an attempt to confirm the reported findings, and to investigate the uses of the products.