A Level Chemistry OCR Practice Exam

What characterizes electrophilic addition reactions?

1. Elimination of hydrogen and oxygen from a compound

2. An electrophile is attracted to an electron-rich atom

3. Formation of an ionic bond between two atoms

4. Breaking of a covalent bond in an alkane

The correct answer is: An electrophile is attracted to an electron-rich atom

Electrophilic addition reactions are characterized by the interaction between an electrophile and a nucleophile. In these reactions, the electrophile, which is a species that seeks to gain electrons, is attracted to an electron-rich atom within a molecule, typically containing pi bonds like alkenes or alkynes. This electron-deficient species reacts with the nucleophile, facilitating the addition of new atoms or groups to the molecule. This process distinctly contrasts with options that describe different mechanisms. The elimination of hydrogen and oxygen from a compound would involve a loss of atoms rather than the addition characteristic of electrophilic reactions. The formation of an ionic bond pertains more to the transfer of electrons rather than the specific nucleophilic and electrophilic interactions seen in addition reactions. Lastly, breaking a covalent bond in an alkane does not directly pertain to electrophilic addition, as alkanes are generally stable and less reactive compared to alkenes or alkynes, which are more commonly involved in these types of reactions. Thus, the essence of electrophilic addition lies in the attraction of the electrophile to the electron-rich atom, leading to the incorporation of new components into the molecular structure.