Which solvent, ethanol or dimethyl sulfoxide, would be better for carrying out the given reaction is to be determined. Concept introduction: Polar aprotic solvents favor S N 2/E2 reactions. In S N 2 reaction, the nucleophile starts forming a bond with the electrophilic carbon before the leaving group has departed. In E2 reaction, the attacking species acts as a base, removing an acidic proton. In general, strong negatively charged nucleophiles (or bases) work best in these reactions. Negatively charged species are strongly solvated by protic solvents, reducing their strength as a nucleophile or a base. Aprotic solvents do not effectively solvate the nucleophile/base, and therefore, work better. Polar protic solvents favor S N 1/E1 reactions. Both reactions start the same way. The leaving group departs or the base extracts an acidic proton to form a carbocation in the first step. The nucleophile/base is not involved in this step. A protic solvent will therefore promote an S N 1/E1 reaction in two ways; by stabilizing the carbocation as well as the nucleophile/base.

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Chapter 9, Problem 9.59P

Interpretation Introduction

Interpretation:

Which solvent, ethanol or dimethyl sulfoxide, would be better for carrying out the given reaction is to be determined.

Concept introduction:

Polar aprotic solvents favor SN2/E2 reactions. In SN2 reaction, the nucleophile starts forming a bond with the electrophilic carbon before the leaving group has departed. In E2 reaction, the attacking species acts as a base, removing an acidic proton. In general, strong negatively charged nucleophiles (or bases) work best in these reactions. Negatively charged species are strongly solvated by protic solvents, reducing their strength as a nucleophile or a base. Aprotic solvents do not effectively solvate the nucleophile/base, and therefore, work better.

Polar protic solvents favor SN1/E1 reactions. Both reactions start the same way. The leaving group departs or the base extracts an acidic proton to form a carbocation in the first step. The nucleophile/base is not involved in this step. A protic solvent will therefore promote an SN1/E1 reaction in two ways; by stabilizing the carbocation as well as the nucleophile/base.

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