The Student Room Group

Mesomeric effects

I am comparing the stability of the two following carbocations:

1. PhCH=CHCH2(+)
2. CH3CH=CHCH2(+)

Now instinctively I am thinking 1 is more stable than 2 because of greater mesomeric effect and so the (+) charge can be delocalised around the molecule more so than 2...but how would I draw resonance structures for 2? Can a pair of electrons leave the phenyl group and form a double bond to adjacent C as a resonance form?
Original post by waldonator
I am comparing the stability of the two following carbocations:

1. PhCH=CHCH2(+)
2. CH3CH=CHCH2(+)

Now instinctively I am thinking 1 is more stable than 2 because of greater mesomeric effect and so the (+) charge can be delocalised around the molecule more so than 2...but how would I draw resonance structures for 2? Can a pair of electrons leave the phenyl group and form a double bond to adjacent C as a resonance form?


You mean how would you draw for 1. Yes, you can draw structures where the + is localised on the carbon atoms in the aromatic ring.

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