A theoretical study of chemical reactivity of tartrazine through DFT reactivity descriptors.

In this work we have calculated global and local DFT reactivitydescriptors for tartrazine at B3LYP/6-311++G (2d,2p) level.Global reactivity descriptors such as ionization energy, molecularhardness, electrophilicity, and total energies were calculated to evaluatethe tartrazine reactivity in aqueous and gas conditions. Local reactivitywas evaluated through the Fukui function. The influence ofthe solvent was taken into account with the PCM model. The resultsindicate that the solvation process modifies the reactivity descriptorsvalues. From our results, it was found that an electrophilic attack allowsa direct cleavage of the N=N bond. If a nucleophilic attack isconsidered as initial attack, it is necessary a second attack by free radicalsor electrophiles to cleave the N=N bond. In the case of an initialattack by free radicals, tartrazine requires a subsequent nucleophilicattack to cleave the N=N bond.