Spectroscopic and DFT evaluation of the positional effect of amino group on the properties of aminobenzenesulphonic acid: solvents interactions

Positional effect of NH₂ group on the properties of aminobenzenesulphonic acid (AMBSA) has been investigated. Potential energy scan (PES) calculation revealed the energy difference between the two global minima predicted for each of the derivatives to be decreasing with the increasing distance between the –NH₂ substituent and the –SO₃H moiety. On the other hand, the zero-point energy affirmed the ortho and para substituted AMBSAs as being more stable than the meta counterpart by 1.7 kcal/mol. The derivatives showed comparable chemical reactivity, whereas the simulation of their solubility in the selected solvents affirmed the 4-aminobenzenesulphonic acid to be generally more soluble than the other derivatives. Application of Kamlet–Taft model on the absorption data of the aminobenzenesulphonic acids revealed the influence of solvent polarity together with hydrogen bonding ability on their solubility. On the part of vibrational property, the vibrational modes associated with –SO₃H moiety were found to be sensitive to the position of amino substituent.