orbitals—diatomic molecules 88 -- Bonds between different atoms 95 -- Hybridization of atomic orbitals 99 -- Rotation spectra 148 -- The allyl system 150 -- Delocalization over three atoms is a common -- structural feature and rearrangement reactions 358 -- Further reading 359 -- fFH Conformational analysis 360 -- Bond rotation atoms to adopt a number of conformations 360 -- Conformation and configuration 361 -- Barriers to rotation The role of the leaving group 390 -- E1 reactions can be stereoselective 391 -- E2 eliminations have anti-periplanar