IR studies in the substituted benzaldehyde series provide a new definition of sigma-plus constants of ionic substituents.
Fourier-transform IR frequencies nu(C=O) and integrated intensities A(C=O) of the carbonyl groups of a series of benzaldehydes (53 compounds) have been measured in dimethyl sulphoxide. Excellent and satisfactory correlations have been found between nu(C=O) and sigma(+) substituent constants of the m- and p-substituted compounds. Diortho-substituted compounds deviate strongly from the correlation lines because of the steric ortho-effects mainly. sigma(+) constants of ionic substituents (10 examples) have proved satisfactorily valid in the series studied.
Institute of Organic Chemistry, Bulgarian Academy of Sciences, Acad G Bonchev Str, Sofia 1113, Bulgaria. ev@orgchm.bas.bg
Evelina A
EA
Velcheva
Ivan N
IN
Juchnovski
Ivan G
IG
Binev
D001547:Benzaldehydes / Q000737:chemistry*; D004121:Dimethyl Sulfoxide / Q000737:chemistry; D007477:Ions; D013055:Spectrophotometry, Infrared / Q000379:methods*; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*
D001547:Benzaldehydes; D007477:Ions; C032175:benzaldehyde; D004121:Dimethyl Sulfoxide