Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: eXpertiz on February 09, 2014, 10:24:17 AM
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Hi guys!
I have a question and exam is closing in really fast. I hope you can help me :)
The problem is as follows: Arrange the carbocations by increasing stability.
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Thanks and cheers!
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eXpertiz,
You need to go back to basics. Term I of organic chemistry, and really understand carbocations. Then you need to review resonance structures.
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I understand most of the basic pre-reactions organic chemistry. I've mastered resonance just recently. I just don't now how to apply these terms when it comes to stability. Could you be more specific, please? :)
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This is a question whose foundation lays in resonance and induction. Show some work.
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I understand most of the basic pre-reactions organic chemistry. I've mastered resonance just recently. I just don't now how to apply these terms when it comes to stability. Could you be more specific, please? :)
In that case draw all of the resonance structures for the given compounds. Are any of the structures particularly unstable or stable (more completed octets)?
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Resonance structures of the first example have always 1 incompleted octet rule, when the bonds ie. pi electrons are transfered around the ring and thus the positive charge. Hence, the structure is unstable.
For the second example, resonance structures exist where there are 2 incompleted octets, one positive charge is transfered around the ring while the other stays on the CH2 group. Hence, the structure is very unstable.
And for the third example, there exists a resonance structure, where there are 0 incompleted octets, the positive charge is on oxygen of the OMe group, but oxygen fulfills the octet rule. Thus, this is the most stable carbocation.
The order of increasing stability is as follows: 2. example < 1. example < 3. example.
Is this understanding correct by any chance? :)
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That is the order I had as well and you figured it out yourself. Kudos.
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Thank you! :)