Comparison of the H-1 and C-13 NMR spectra of a series of substituted 5-benzylidene-N,N'-dimethylbarbituric acids (1) revealed chemical-shift variations of different centers that correlated with the theoretical electrophilicities or with the substituent electrophilic constant sigma(omega), in an example of the usefulness of these DFT-based indices. Copyright (c) 2012 John Wiley & Sons, Ltd.