1137-1140Absorption spectra
of ten 3-N-alkyl-5-carboxy uracils are recorded in fourteen solvents in the
range 200-400 nm. The absorption frequencies of carboxy carbonyl electronic transitions
are correlated by dual substituent parameter (DSP) treatment involving both
polar (σ*) and steric (Es or vc) substituent constants.
The effect of solvent polarity and solvent/solute hydrogen bonding interactions
on the absorption spectra are interpreted by means of linear solvation energy relationships
(LSER) using a general equation of the form v = vo + sπ*
+ bβ + aα where π* is a measure of the solvent polarity, β is the scale
of the solvent hydrogen bond acceptor basicities and a is the scale of the solvent
hydrogen bond donor acidities