Which of the following is the correct order of decreasing stability?

Atropylium (cyclohepta-2,4,6-trien-1-ylium) $>$ $C X_{6} H X_{5} CH X_{2} X^{+}$ $>$ $CH X_{3} CH X_{2} X^{+}$ $>$ $CH X_{2} = CH X^{+}$
Btropylium $>$ $CH X_{3} CH X_{2} X^{+}$ $>$ $C X_{6} H X_{5} CH X_{2} X^{+}$ $>$ $CH X_{2} = CH X^{+}$
C $C X_{6} H X_{5} CH X_{2} X^{+}$ $>$ tropylium $>$ $CH X_{3} CH X_{2} X^{+}$ $>$ $CH X_{2} = CH X^{+}$
Dtropylium $>$ $C X_{6} H X_{5} CH X_{2} X^{+}$ $>$ $CH X_{2} = CH X^{+}$ $>$ $CH X_{3} CH X_{2} X^{+}$

Answer: A

Tropylium has 6 pi electrons delocalised over 7 carbons (aromatic) and is isolable as salts, so it is the most stable. Benzyl cation is resonance stabilised. Ethyl cation has hyperconjugation only, and the vinyl cation (charge on an

s p

carbon, no stabilisation) is the least stable.

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Which of the following is the correct order of decreasing stability?

Answer: A

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