Reactions of unsaturated compounds

This chapter assesses reactions of unsaturated compounds, focusing on electrophilic addition. In general, electrophilic addition reactions occur between an electrophile and an alkene, though other groups possessing π-bonds may also react in this way. Electrophilic addition results in the π-bond breaking with the formation of two new σ bonds, with the electrophile 'adding' to the alkene to form a new, larger, molecule. The chapter shows an example electrophilic addition in which hydrogen bromide 'adds' to an alkene π-bond. Common reagents which undergo electrophilic addition to alkenes are hydrogen halides, alcohols, and water. Acid catalysts are often used which act as an electrophile, reacting with the alkene in the first instance to form a carbocation, which is then attacked by a nucleophile.