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Topic: Which one is more stable ; CH3+ or CH3-CHCl+?  (Read 8766 times)

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Offline Ahmed Abdullah

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Which one is more stable ; CH3+ or CH3-CHCl+?
« on: May 14, 2008, 05:39:12 AM »

CH3-CHCl+ should be more more stable since CH3- is connected to the positive carbon atom and CH3 is electron donating. But the positive carbon is also attached to Cl which is electron withdrawing agent. So I am not sure. Cl has lone pair so the positive charge can resonate between C and Cl atom. Can the resonance structure can suppress the instability due to electron withdrawing property of Cl?

Please help.

Offline AWK

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Re: Which one is more stable ; CH3+ or CH3-CHCl+?
« Reply #1 on: May 14, 2008, 06:20:55 AM »
If a resonce is possible, this structure is more stable.
AWK

Offline Ahmed Abdullah

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Re: Which one is more stable ; CH3+ or CH3-CHCl+?
« Reply #2 on: May 15, 2008, 01:51:56 AM »
Another question, does CH3-group stabilize carbocation by inductive effect or by hyperconjugation? OR by Both!

Offline AWK

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AWK

Offline Ahmed Abdullah

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Re: Which one is more stable ; CH3+ or CH3-CHCl+?
« Reply #4 on: May 16, 2008, 11:56:18 PM »
http://www.iupac.org/goldbook/I03021.pdf
http://www.iupac.org/goldbook/H02924.pdf

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Well, I understand both inductive and hyperconjugation plays a role here. But I want to know which one bears the major effect.

Offline Ahmed Abdullah

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Re: Which one is more stable ; CH3+ or CH3-CHCl+?
« Reply #5 on: May 17, 2008, 03:40:40 AM »
http://www.iupac.org/goldbook/I03021.pdf
http://www.iupac.org/goldbook/H02924.pdf

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Well, I understand both inductive and hyperconjugation plays a role here. But I want to know which one bears the major effect.
To illustrate the role of hyperconjugation and inductive effect in stabilizing carbocation I have devicd up an example. Suppose two carbocation N+H3-C+H2 and BeH2-C+H2.  N+H3- group is more electron withdrawing; it means it has negative inductive effect but it can stabilize the carbocation through hyperconjugation. BeH2- group is electron donating (inductive effect) but hyperconjugation is not favourable for it coz BeH2-C+H2 is sp2 hybridized.
Now which one would be more stable? it will provide some indication about the dominant effect ..
Thx in anticipation

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