CHEM 211 Lecture Notes - Lecture 26: Transesterification, Protic Solvent, Trigonal Planar Molecular Geometry
10 Nov 2016
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Carbocations: tertiary secondary primary methyl. Tertiary carbocations are the most stable: trigonal planar, partial positive central atom, the more substituents, the more inductive donation of electron density. Stabilizes the positive charge: hyper conjugation. Bonding electrons stabilizes empty p orbitals through hyper conjugation. Sn2: methyl primary secondary. Need room for the nucleophile to move in, so the less dense the better: sn2 needs a charged nucleophile with a lone pair. Solvolysis = when the solvent acts the nucleophile: only happens in sn1, not sn2, hydrolysis = solvolysis with water. water is the nucleophile, methanolysis = when methane acts as the nucleophile. Factors that affect the rate: 1. the substrate - is it secondary? primary? etc, 2. the nucleophile - if it"s strong, it"s sn2. if it"s neutral, sn1. Between a tertiary and an ion, the tertiary wins, so sn1: 3. the solvent, 4. the leaving group. Vinyl and aryl groups do not undergo sn2 reactions.
