chemistry

S N 2 reactions and solvent effects Polar aprotic solvents – solvents that do not have acidic proton such as DMSO, DMF, CH 3 CN, HMPA - accelerate the rate of  S N 2 reactions by solvating the cation thus making the nucleophile more available to react. On the contrary, protic solvents such as alcohols or amines decrease the rate of S N 2 reactions since they tend to solvate nucleophiles (Fig. 1). The partial positive charge that exists in the O-H hydrogens solvate the negative charge of the nucleophile (Nu: - ) . Solvated nucleophiles are held tightly and  are unable to react with the electrophilic substrates – compounds that have leaving group. Fig. 1: Partially positively charged hydrogens from polar O-H bonds solvate partially negative charge of the nucleophile. Solvated nucleophiles – as the one shown above – are unable to react with electrophilic substrates. The effect of solvents on the rate of S N 2 nucleophilic substitution reactions is shown in Fig. 2. Fig. 2:...