If the inductive effect operates purely through electronegativity differences, how come the methyl group is considered to donate electrons through the inductive effect? My textbook says that there is negligible electronegativity difference between carbon and hydrogen, and definitely none between two carbon atoms, then how come CH3 shows the +I effect?

Reading other similar questions on CSE, (Why is the methyl group electron-donating via the inductive effect?) the answers seem to say that hyperconjugation is the reason for the inductive effect, which I cannot grasp at all.

As far as I've read, hyperconjugation does not depend on electronegativity at all, then how come both the effects are related in any way?

Coming back to the question, why exactly is CH3 a +I group?

  • $\begingroup$ It makes some acids weaker then -H group, and not via resonance - that's about how much reason such rules of thumb need. $\endgroup$
    – Mithoron
    Jul 20, 2021 at 15:50
  • $\begingroup$ And if it actually does make them weaker depends largely on solvent effects (or lack of thereof). $\endgroup$
    – Mithoron
    Jul 20, 2021 at 15:57

1 Answer 1


Hi when there is a bond b/w H and C there is a slight charge speration like this enter image description here

In methyl there are three H so it looks like this

Notice the delta negative charge on carbon this is enough for carbon to "donate electron"

When case is with ter. carbocation the delta negative charge is satisfying positive charge of carbocation stabilizing it so


So it is a +I group

  • $\begingroup$ @napstablook what is the purpose of your comment $\endgroup$ Aug 1, 2021 at 10:27
  • $\begingroup$ Is something wrong in the answer $\endgroup$ Aug 1, 2021 at 10:28
  • $\begingroup$ Nevermind, it was a misunderstanding, I wanted to post it under the question. I didn't downvote anyways. $\endgroup$ Aug 1, 2021 at 10:28

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