Nitration of triptycene in acetic anhydride

Abstract

Nitration in acetic anhydride of one ring of triptycene deactivates nitration in either of the other rings by a factor of 5.5. For triptycene, the β-partial rate factor is 67, whilst that for the α-position is 1.6. It is shown that, as in acid-catalysed detritiation, (i) transannular resonance effects are not important and (ii) the decrease in bond order from 1.5 in the ground state to ca. 1.3 in the transition state for the bond fusing the aromatic and aliphatic rings makes a significant contribution in determining reactivity at the β-position.