When considering the hyperconjugative (+H) effect of isotopic methyl groups, the correct decreasing — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

Hyperconjugation involves the partial breaking of the $\alpha-C-H$ bond. Because heavier isotopes form stronger bonds ($C-T > C-D > C-H$), they are harder to break and participate poorly in no-bond resonance. Thus, $-CH_3$ provides the strongest +H effect.