CHM 25500 Lecture Notes - Lecture 29: Nucleophilic Substitution, Sn2 Reaction, Protic Solvent
4 Aug 2015
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Document Summary
Chm 255 - lecture 29 - solvents and nucleophilicity. Nucleophilic substitution reactions are carried out in the midst of solvents. The type of solvent determines the rate of sn2 reaction. Protic solvents are solvents that have both hydrogen bond donors and hydrogen bond acceptors. Protic solvents solvate the nucleophile by interacting with it through hydrogen bonds. Polar aprotic solvents do not have hydrogen bond donor sites. Protic solvents stabilize the nucleophile by solvating it, causing the reactants side of the equation to be lower in energy and resulting in a higher activation energy for the reaction, meaning the reaction is slower. Aprotic solvents do not stabilize the nucleophile meaning the reactants are higher in energy and the activation energy of the reaction is smaller, resulting in a faster reaction. In sn1 reactions, the leaving group leaves first, resulting in a carbocation intermediate, which the nucleophile can attack from either side.
