Direct and indirect substituent effects on 1J(CH) in vinyl derivatives and related compounds

✍ Scribed by D. F. Ewing

• Book ID: 102951766
• Publisher: John Wiley and Sons
• Year: 1973
• Tongue: English
• Weight: 603 KB
• Volume: 5
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1270051204

✦ Synopsis

Abstract

The variation in the one–bond couplings ^1^J(CH) in vinyl derivatives with substituent has been examined. For the geminal proton ^1^J correlates very badly with substituent electronegativity but extremely well with σ~I~, if conjugating substituents are excluded. In the case of halogen substituents the marked stereospecificity of ^1^J(CH) for the cis and trans protons can be rationalised in terms of an intrinsic dependence of π~CH~ on the dihedral angle between the coupling atoms and the perturbing substituent, with an additional positive increment to the cis coupling due to direct interaction of the substituent non‐bonding electrons or to orbital circulation of the substituent electrons. The intrinsic specificity of β‐substituent effects on ^1^J(CH) is also found in analogous compounds containing CN and CO bonds.