The result? The beautiful, stable, aromatic ring is temporarily broken. The positive charge is no longer delocalized over six carbons; it’s localized on the sp³ carbon and its neighbors.
When you hear the word “onium,” you might think of ammonium (NH₄⁺) or sulfonium (H₃S⁺). But tucked within this family is a less famous, yet critically important, member: Aronium . aronium
If you’ve ever picked up a can of soda, cleaned a stain with vinegar, or studied biochemistry, you’ve indirectly relied on aronium ions. They are the fleeting, high-energy ghosts that make some of the most fundamental reactions in chemistry possible. The result
| Name | Structure | Notes | |------|-----------|-------| | | C₆H₇⁺ | The simplest; protonated benzene. | | Naphthalenium | C₁₀H₉⁺ | Protonated naphthalene; can form at two different positions (1- or 2-naphthalenium). | | Tropylium | C₇H₇⁺ | The exception! This is stable and aromatic (7 π-electrons, Hückel’s rule). Often compared/contrasted with aronium. | | Protonated arenes | Various | Any aromatic compound with an extra H⁺ on a ring carbon. | When you hear the word “onium,” you might