Correlazione di dati spettrometrici RMN con le costanti σ di Hammett in cumarine 6 e 7 sostituite
In order to establish the reactivity of positions 3 an d 4 in substituted coumarins, the values of the chemical shifts in several coumarins have been correlated with the σ Hammett constant. The statistically results computed show that there is a direct relation between the frequencies of proton 3 in the NMR spectra and the Hammett constant, whereas no direct correlation is possible for position 4 due to the conjugation of the carbonyl group.