• # question_answer Most stable carbonium ion is [Pb. CET 2004] A) ${{\overset{+}{\mathop{C}}\,}_{2}}{{H}_{5}}$ B) ${{(C{{H}_{3}})}_{3}}\overset{+}{\mathop{C}}\,$ C) ${{({{C}_{6}}{{H}_{5}})}_{3}}\overset{+}{\mathop{C}}\,$ D) ${{C}_{6}}{{H}_{5}}\overset{+}{\mathop{C}}\,{{H}_{2}}$

In the triphenyl methyl carbonium ion the p electrons of all the three benzene rings are delocalised with the vacant p-orbital of central carbon atom. So, it is resonance stabilised. It is the most stable of all the carbonium ions given The ion $C{{H}_{3}}-\underset{C{{H}_{3}}}{\overset{C{{H}_{3}}}{\mathop{\underset{|\ \ }{\overset{|\ \ }{\mathop{{{C}^{+}}}}}\,\ \ }}}\,$ is stabilised by hyperconjugation, a second order resonance.