Four cyclohexadienyl cation intermediates (arenium ions) are described below. Assume all rings are six-membered with the substituents and features as specified: (I) An -OCH₃ group is attached to C₁ . The carbon C₁ bears a positive charge. C₄ is an sp^3 hybridized carbon. Double bonds are present between C₂=C₃ and C₅=C₆ . (II) An -OCH₃ group is attached to C₁ . The carbon C₂ bears a positive charge. C₃ is an sp^3 hybr

Step-by-step solution

In structure (I), the positive charge is located on C₁ , which is directly attached to the -OCH₃ group. The oxygen atom of the -OCH₃ group has lone pairs of electrons. It can donate a lone pair to the adjacent positively charged carbon, forming a carbon-oxygen double bond ( -bond). This resonance structure allows every atom (except hydrogen) to achieve a complete octet, making it exceptionally stable. In structure (II), the positive charge is on C₂ , so the oxygen lone pair cannot participate in direct resonance st