Acyclic hydrocarbons: Alkenes

Publisher Summary This chapter discusses the structure, properties, and theoretical considerations of acyclic hydrocarbons: alkenes. A dynamic nuclear magnetic resonance (NMR) study has investigated the rotation about alkyl-alkene bonds using substituted isopropylethenes. In the studies of sterically hindered alkenes, a number of attempts have been made to synthesise tetra-tert-butylethene. However, the tetraaldehyde, obtained by metathesis of the alkene is the precursor closest to that has yet been obtained. A theoretical study of the structure and stability of protonated alkenes in both the gas phase and in solution has shown that there is a distinction between alkenes which have an equal number of alkyl substituents on both sides of the double bond and those which have a different number. In the latter case no bridged carbenium ions could be defined. However, the effect of solvents has a profound effect on the stability of the cationic structures, and it changes the gas phase data remarkably.