IR spectral and structural studies of 4‐aminobenzenesulfonamide (sulfanilamide)‐d₀, ‐d₄, and ‐¹⁵N, as well as their azanions: Combined DFT B3LYP/experimental approach

Abstract

Abstract The infrared (IR) spectra of sulfanilamide 1 and of its azanion (counter ion Na + ) 2 have been measured in dimethyl sulfoxide (DMSO) solutions. The density functional theory (DFT) B3LYP 6‐31++G( d , p ) computations performed adequately describe the experimental spectroscopic data, including the corresponding frequency isotopic shifts. In agreement between theory and experiment, the conversion of sulfanilamide 1 into azanion 2 results in strong frequency decreases of the asymmetrical and symmetrical vibrations of the SO 2 group: predicted 122 cm −1 , measured 140 cm −1 in solution (total values), as well as in other essential IR spectral changes. According to the computations, the strongest changes in the steric structure take place at and next to the azanionic center. The new (azanionic) charge is distributed, as follows: 0.08e − , 0.23e − , and 0.12e − are delocalized over the amino, phenylene, and sulfonic groups, respectively, and 0.57e − of it remain localized at the azanionic center. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007