What is an electrophile?

• A. A nucleophile
• B. An electron pair donor
• C. An electron pair acceptor
• D. A radical species

Answer: (C)

An electrophile is an electron pair acceptor. In Lewis theory, it behaves as a Lewis acid, seeking to accept an electron pair from a nucleophile (the Lewis base) to form a bond. This happens because the electrophile has an electron-deficient center—often a positively charged atom or an atom with an empty orbital—that can accept electrons. Common examples include a proton (H+) and boron trifluoride (BF3). In reactions, the nucleophile donates a lone pair to the electrophile, creating a new covalent bond. A nucleophile is an electron pair donor, not an acceptor, so it is on the opposite side of this interaction. A radical species involves an unpaired electron and is not defined primarily as an electron pair acceptor, though some reactions can involve radicals in other roles.