Why is a 3° Carbanion unstable than 1° Carbanion? Carbon atom with negative charge will become little electropositive relative to a neutral carbon. So if a Carbanion is attached to three neutral carbons, essentially it should donate it's electrons distributing the negative charge of -1, thus stabilizing it. By this logic, more carbon atoms attached means more stability. But this does not happen. 1° Carbanion is most stable. Why?
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You are half way through explaining the question yourself. You just need to realise that alkyl groups themselves are electron donating groups. – Jun 22 '20 at 01:26
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Why that is my question they should be more Electronegative than the negatively charged carbon, thereby accepting electrons. – Yash Sinhal Jun 22 '20 at 03:04
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To make it common knowledge, I am a high school student. For my reasoning I have considered only the Inductive effect which is basically electron density movement from less to more Electronegative atom. I have even not considered C-H bond polarity in alkyl group nor the hyperconjugation effect. Please tell me what I am missing particularly and why my logic is wrong? – Yash Sinhal Jun 22 '20 at 03:16
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Methyl group is EDG and exerts +I effect due to Hyperconjugation. Related: Why is the methyl group electron-donating via the inductive effect? and What is Hyperconjugation? – Aniruddha Deb Jun 22 '20 at 03:19
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4Does this answer your question? Why is the methyl group electron-donating via the inductive effect? – Aniruddha Deb Jun 22 '20 at 03:21
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The above links explain why vicinal C-H bonds stabilize carbocations. I think the OP is looking for an explanation for carbanions that is essentally not just "Oh! It's the reverse order of carbocations". – user55119 Jun 22 '20 at 12:21
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Carbanions and Carbocations are perfectly opposite in order of stability because they are opposite in order of charge. The order is preferred of carbocations the same as acidity by Lewis' nucleophile/electrophile definition. Therefore, because a positive charge is stabilized better by a tertiary carbon, it is preferred to host a carbocation because the electron shells of its substituent carbons help stabilize the charge.
In the case of a carbanion, the negative charge is best stabilized when not in contact with neighboring nuclei that would resonate the negative charge away from the nucleophilic site. If you think about it like sterics, the further away the negative charge can be from other substituents, the better in the case of carbanions.
Moobius Strip
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