3.4 Electron-pair sharing reactions

• Donate electron pair to electrophile

• Recognize nucleophiles as electron-rich species

• Nucleophile donates pair, forms new bond

• Another bond breaks, leaving group departs

• Deduce substitution products from nucleophile and leaving group

• Both electrons stay with one fragment

• Forms ions

• Use curly arrows to show electron-pair movement

• Accept electron pair from nucleophile

• Recognize electrophiles as electron-deficient species

• High electron density at C=C bond

• Reactions: + H₂O, + halogens, + hydrogen halides

• Deduce alkene addition equations; SL mechanisms are not assessed

• Lewis acid = electron-pair acceptor

• Lewis base = electron-pair donor

• Classify nucleophiles/electrophiles using Lewis acid-base theory

• Lewis base + Lewis acid

• Nucleophiles = Lewis bases

• Electrophiles = Lewis acids

• Explain coordination bond formation with electron-pair donation

• Ligands donate electron pairs to transition metal cations

• Identify ligands and central transition metal cations in complex ions

• Primary halogenoalkanes: SN2

• Tertiary halogenoalkanes: SN1

• Distinguish one-step SN2 and two-step SN1; include stereospecific SN2

• Identity influences rate

• Link carbon-halogen bond enthalpy and polarity to reaction rate

• Symmetrical alkenes + halogens/water/HX

• Describe mechanisms with curly arrows and carbocation/halonium intermediates as appropriate

• Unsymmetrical alkenes + HX or H₂O

• Major product from more stable carbocation

• Predict and explain major products from carbocation stability

• Mechanism with charged electrophile E⁺

• Formation of the electrophile is not assessed