Which statement correctly describes the roles of nucleophiles and electrophiles?

Which statement correctly describes the roles of nucleophiles and electrophiles?

• A. Nucleophile is an electron pair donor; electrophile is an electron pair acceptor
• B. Nucleophile is an electron pair acceptor; electrophile is an electron pair donor
• C. Both nucleophile and electrophile donate electrons
• D. Both nucleophile and electrophile accept electrons

Answer: (A)

In many reactions, electron flow goes from a nucleophile to an electrophile. A nucleophile has lone pairs or π electrons that it can donate, so it acts as an electron pair donor. An electrophile has an electron-poor center or an empty orbital that can accept electrons, so it acts as an electron pair acceptor. This pairing explains why the best description is that a nucleophile donates electron density while an electrophile accepts it. For example, a nucleophile like hydroxide can donate its lone pair to a carbon atom that is part of a carbon–halogen bond, forming a bond while the leaving group departs, and an electrophile like a proton accepts electron density from the nucleophile. The other options imply that both species either donate or both accept, which would not explain the formation of bonds in these reactions.

In many reactions, electron flow goes from a nucleophile to an electrophile. A nucleophile has lone pairs or π electrons that it can donate, so it acts as an electron pair donor. An electrophile has an electron-poor center or an empty orbital that can accept electrons, so it acts as an electron pair acceptor. This pairing explains why the best description is that a nucleophile donates electron density while an electrophile accepts it. For example, a nucleophile like hydroxide can donate its lone pair to a carbon atom that is part of a carbon–halogen bond, forming a bond while the leaving group departs, and an electrophile like a proton accepts electron density from the nucleophile. The other options imply that both species either donate or both accept, which would not explain the formation of bonds in these reactions.