CHEM 211 Chapter Notes - Chapter 6.18-6.19: Nucleophile, Weak Base, Molecularity
8 Dec 2016
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Sn2 vs e2: both favored by high concentration of nucleophile or base. When nucleophile attacks c carrying the leaving group = sn2: factors that this is dependent on are temperature, size of the base/nucleophile, and effects of basicity and polarizability. Labelling for the reaction arrow: reagents are written above, solvent and temperature written below. Very basic primary halides are usually substitution favored: because can easily approach the carbon, secondary substrate. Very basic secondary halides favor elimination because of steric hindrance (makes substitution harder: tertiary substrate. Tertiary halides can not undergo sn2 because of steric hindrance. Either elimination or sn1 (but sn1 usually is minor product) Temperature effects: increasing temperatures favor elimination because e1 and e2 require a high free energy of activation. And elimination is more entropically favored over substitution because it generates more nal products, making it more entropic.
