Conjugation vs hyperconjugation in molecular structure of acrolein

► The geometry of acrolein does not correspond to expected one. ► Besides π-π conjugation n → σ∗ hyperconjugation is observed in acrolein. ► π-π conjugative and n → σ∗ hyperconjugative interactions have close energy. ► π-π and n → σ∗ influence on the Csp2-Csp2 bond length in opposite directions. ► The Csp2-Csp2 bond length correlates with the difference between two interactions.