CHEM164 Lecture Notes - Lecture 3: Rate-Determining Step, Nucleophilic Substitution, Sn2 Reaction
16 Jul 2016
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Nucleophile is an electron rich species (lone pair of electrons) capable of reacting with electron poor species (electrophile) Nucleophilic substitution reactions involve nucleophile attacking substrate containing sp3 hybridized carbon attached to leaving group. These substitution reactions allow for functional group inter conversions to occur, thus allowing preparation of new organic compounds. For nucleophilic substitution to occur, substrate should have a good leaving group (lg) Good leaving groups are substituents that can leave as stable anions (ex. Several factors affect nucleophilic substitution reactions: substrate structure, nature of the leaving group (lg, nucleophile reactivity (sn2 only, solvent effects. Two types of nucleophilic substitution reactions: sn1 and sn2. Sn1 reactions are uni molecular reactions ( rst order overall) ie. rate determining step is dependent only on concentration of one species (substrate) First step is a slow, rate determining step where leaving group departs to form a carbocation (highly endothermic). This is followed by rapid addition of nucleophile to carbocation.
