The Molecular Structure of Allenes and Ketenes, XII [1] Four-Bond Proton-Proton Spin-Spin Couplings in Allenes

Abstract

<jats:title>Abstract</jats:title><jats:p> Four-bond proton-proton coupling constants in allenes are reported. The substituent effects on the coupling constants are discussed on the basis of the dual-substituent parameter approach. Furthermore, the coupling constants are related to quantum-chemical indices (electron densities, overlap populations) obtained from semiempirical CNDO/S and ab initio STO-3G calculations.</jats:p><jats:p>The magnitudes of the coupling constants depend upon the polar natures of the substituents as well as upon their charge-transfer abilities (resonance effects) to a com-parable amount.</jats:p><jats:p>In general, the coupling constants in 1,3-disubstituted allenes are nonadditive in ligand -specific parameters.</jats:p>