Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

Reactions of R²,R³-alkyl substituted 2-hydroxybenzenecarboxylic acids 2-HO-C₆H₂R₂-COOH with Grignard reagents R¹MgBr in the presence of nickel give stable aryl alkyl ketyl radicals 2-O^--R²-, R³-C₆H₂-CO^--R¹ where R¹ = CH₃, C₂H₅, C₂D₅, n-C₃H₇ and R²,R³ = CH₃, C₂H₅, i-C₃H₇, t-C₄H₉. The β protons of ketyl group are equivalent (splitting constant 1.25 mT) and non-equivalent (splitting constants within 0.5 to 1.5 mT) for R¹ = methyl and other alkyl groups, respectively. Interaction of the γ protons with the unpaired electron was only observed in the case of R¹ = n-propyl (splitting constants about 0.07 mT). The substituents R¹ have but slight effect on values of splitting constants of the protons in R²,R³ and vice versa. Also splitting constants of the benzene nucleus (a₄^H = 0.55 mT, a₆^H = 0.44 mT) are only slightly affected by the substituents R¹,R²,R³, which indicates dominant electron-donor effect of the oxido-anion group eliminating the relatively smaller contributions of the alkyl substituents.