Chapter 2 - Unsaturated acyclic hydrocarbons

Abstract

Publisher Summary This chapter examines the methods of preparation, properties, stereochemical aspects and typical reactions of carbenes, alkenes, allenes, dienes, and acetylenes or alkynes. Carbenes may be prepared from diazocompounds, cycloeliminations, base-catalyzed α-eliminations, and Simmons-Smith and related methylene transfers. Carbenes undergo typical reactions, such as cycloadditions, insertions, rearrangements, and transition metal complexes. Several powerful methods have been developed for the stereoselective synthesis of alkenes. These include eliminations of HX, dehalogenation of vicinal dihalides, decarboxylation of hydroxy acids, Wittig reaction and related procedures, such as partial reduction, and hydroboration of alkynes. Alkenes undergo various chemical reactions, such as electrophilic additions, addition of halogens and interhalogens, free-radical additions, oxidation, reduction, photochemical reactions, thermal cycloadditions, ene reactions, rearrangements, and metal and metal complex catalyzed reactions. Hydrocarbons containing two double bonds are studied under allenes and dienes; their synthetic methods, properties and typical reactions are analyzed in the chapter. Preparation of acetylenes by dehydrohalogenation methods, metal acetylides, and isomerization of other acetylenes bear specific significance in generation and characteristics of unsaturated acyclic hydrocarbons. Several typical reactions, such as oxidation, reduction, electrophilic addition, such as halogenation, additions of H-X hydrometalation, nucleophilic additions, Diels-Alder cycloadditions, photochemical reactions, cyclo-oligomerization and polymerization are also outlined.