Protic and Dipolar Aprotic Solvent Effects on the Rates of Sn Reactions

2 Protic and Dipolar Aprotic Solvent Effects on the Rates of Sn Reactions 

In the course of a nucleophilic substitution reaction, a new bond is formed between the attacking nucleophile and the substrate. Since the nucleophile attacks with a free 

The potassium salts are solubilized in acetonitrile with [18]crown-6, producing extremely reactive naked anions because of the weak anion solvation forces in acetonitrile solutions and the complete dissociation of the potassium salts [282]. 

Molten triethyl-n-hexylammonium triethyl-n-hexyl-boride as solvent [283]. 

It is apparent that the order of anion nucleophilicity is almost completely reversed on transfer from protic to dipolar non-HBD solvents. Especially for halide ions, the relative reactivity is completely reversed in the two classes of solvents whereas the order of reactivity is I Br Cl F in the protic solvent methanol (reactions no. 1 and no. 2 in Table 5-15), in dipolar non-HBD solvents such as iV,iV-dimethylformamide (no. 2), acetone (no. 3), dimethyl sulfoxide (no. 4), and acetonitrile (no. 5) the sequence of nucleophilicity is reversed. The traditional order of halide nucleophilicities, I Br Cl [261], applies only when the nucleophile is deactivated through solvation by 

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