Introduction: Electron-Pair Sharing Reactions
Many of the most important reactions in organic chemistry can be understood through a single unifying idea: electron-rich species donate electron pairs to electron-deficient species. This section introduces the key players — nucleophiles and electrophiles — and the reaction types they drive, including nucleophilic substitution and electrophilic addition.
To understand why these reactions happen, we also need to understand heterolytic fission — the uneven breaking of covalent bonds that generates the charged intermediates at the heart of these mechanisms.
Think of nucleophiles and electrophiles like puzzle pieces: nucleophiles have an electron-rich "protrusion" (a lone pair or negative charge), while electrophiles have an electron-deficient "gap" (a partial or full positive charge). When they meet, they fit together by forming a new covalent bond.