Chemistry: Your Teacher Lied to You (And Everyone Else)

When I was in class learning about Markovnikov's rule, the whole concept of carbocation stability was drilled into my brain with one golden rule: alkyl groups are electron-donating. We were taught that those little methyl groups act like generous friends, pushing electron density onto that poor, positive carbon atom via the "+I effect", or the inductive effect to save it from collapsing. It made perfect sense on paper and helped us pass our exams.

Turns out, it was also completely wrong.

This is what we call a dogma - beliefs that are essentially considered undeniably true, accepted without proof or questioning. They can hinder scientific progress and oppose the core scientific method of constant inquiry and falsifiability. When dogmas are broken, it can lead to scientific revolutions such as the shift from classical Newtonian physics to quantum mechanics. This is what we call a paradigm shift, a term coined by physicist Thomas Kuhn, occurring when new, contradictory information replaces a dominant, established worldview with a new, more accurate, or useful model.

The Kuhn Cycle, thwink.org

However the new research by Cardiff University, although dismantles a century of textbook dogma, is not a paradigm shift. The framework of the inductive effect is still valid but the discovery merely corrects the direction and magnitude of the effect for specific groups or alkyls.

By using advanced quantum chemical modeling, researchers proved that alkyl groups don't push electrons at all. Rather, they pull them. Because carbon is more electronegative than hydrogen, alkyl groups are actually inductively electron-withdrawing.

To clear up any remaining confusion, if you are currently staring at your screen in a panic wondering how Markovnikov's rule still works, don't worry. What we see in the lab is still the same, it's just the explanation for it that has changed. The reason why tertiary carbocations are most stable isn't because of the inductive effect. Indeed, it's because of hyperconjugation, which is where the overlapping of nearby C-H bonds share their electron density through space. Hyperconjugation is so incredibly powerful that it completely overpowers the fact that the alkyl group is secretly pulling electrons away through the sigma bond.

Hyperconjugation, chem.ucla.edu

While we don't need to throw out our organic chemistry kits, the exam boards are having a total meltdown. Organizations like the AQA are already scrubbing the "+I effect of alkyl groups" from their syllabi. We’ve spent 100 years using the wrong math to get the right answer, and chemistry education is finally having to face the music. We are officially at the Model Crisis stage of the Kuhn Cycle.

References:

AQA. (2025, February 5). AS and A-level Chemistry guidance about alkyl groups. AQA News [1]

Cardiff University. (2024, November 29). Chemistry textbooks need rewriting after new research. Cardiff University News [1]

Elliott, M. C., Hughes, C. E., Knowles, P. J., & Ward, B. D. (2025). Alkyl groups in organic molecules are NOT inductively electron-releasing. Organic & Biomolecular Chemistry, 23(2), 352–359. doi.org [1, 2]

Kuhn, T. S. (2012). The structure of scientific revolutions (4th ed.). University of Chicago Press. (Original work published 1962) [1, 2]

Royal Society of Chemistry. (2025, March 24). Why is the inductive effect making headlines in chemistry education? Education in Chemistry [1]