The Wheland intermediates (and transition states leading to them), due to the tetrahedral environment at the substituting carbon, are not sterically encumbered, and are electronically stabilised at the 1-position (more aromatic resonance structures are possible, ie for the 1-substituted, both an aromatic ring and an allylic cation are possible, but for the 2-substituted, only an aromatic ring with no allylic cation is possible).
The final products, being planar, are sterically hindered in the 1-position (see here: ) but not the 2-position (see here: ). Electronically, they are similar.
| The sulfonylation of Naphthalene | |
|---|---|
| Wheland Intermediate Relative energy: 0.0 | +6 kJ/mol (AM1 calculation) |
| Final Product Relative energy: 0.0 | -10 kJ/mol. |