Infrared spectra and structures of carbanions—XI: Estimation of σ+ constants of anionic substituents

σ⁺ constants of H₂Cxxx- (?11.2), HNxxx- (?7.6), C₂H₅OOC-HCxxx- (?5.0), NC-HCxxx- (?5.4) and some other anionic substituents were estimated on the basis of ν_CN of the corresponding benzonitrile anions and by using the correlations $\text{ν}{}_{\mathrm{<mtext>CN</mtext>}}\text{σ}{}^{\mathrm{+}}$ for benzonitriles, in polar aprotic solvents.