What you’ll learn13 learning objectivesChoose one objective for a focused lesson, or study the complete topic.3.4.1Nucleophiles• Donate electron pair to electrophile• Recognize nucleophiles as electron-rich speciesSyllabus objective3.4.2Nucleophilic substitution• Nucleophile donates pair, forms new bond• Another bond breaks, leaving group departs• Deduce substitution products from nucleophile and leaving groupSyllabus objective3.4.3Heterolytic fission• Both electrons stay with one fragment• Forms ions• Use curly arrows to show electron-pair movementSyllabus objective3.4.4Electrophiles• Accept electron pair from nucleophile• Recognize electrophiles as electron-deficient speciesSyllabus objective3.4.5Electrophilic addition to alkenes• High electron density at C=C bond• Reactions: + H₂O, + halogens, + hydrogen halides• Deduce alkene addition equations; SL mechanisms are not assessedSyllabus objective3.4.6Lewis acid-base theory• Lewis acid = electron-pair acceptor• Lewis base = electron-pair donor• Classify nucleophiles/electrophiles using Lewis acid-base theorySyllabus objective3.4.7Coordination bond formation• Lewis base + Lewis acid• Nucleophiles = Lewis bases• Electrophiles = Lewis acids• Explain coordination bond formation with electron-pair donationSyllabus objective3.4.8Complex ions• Ligands donate electron pairs to transition metal cations• Identify ligands and central transition metal cations in complex ionsSyllabus objective3.4.9(HL)—Nucleophilic substitution mechanisms• Primary halogenoalkanes: SN2• Tertiary halogenoalkanes: SN1• Distinguish one-step SN2 and two-step SN1; include stereospecific SN2Syllabus objective3.4.10(HL)—Leaving group effects• Identity influences rate• Link carbon-halogen bond enthalpy and polarity to reaction rateSyllabus objective3.4.11(HL)—Electrophilic addition mechanisms• Symmetrical alkenes + halogens/water/HX• Describe mechanisms with curly arrows and carbocation/halonium intermediates as appropriateSyllabus objective3.4.12(HL)—Carbocation stability• Unsymmetrical alkenes + HX or H₂O• Major product from more stable carbocation• Predict and explain major products from carbocation stabilitySyllabus objective3.4.13(HL)—Electrophilic substitution in benzene• Mechanism with charged electrophile E⁺• Formation of the electrophile is not assessedSyllabus objective