Modeling the substituent effect on the oxidative degradation of azo dyes

Özen A. S., Aviyente V., De Proft F., Geerlings P.

Journal of Physical Chemistry A, cilt.108, sa.28, ss.5990-6000, 2004 (SCI-Expanded) identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 108 Sayı: 28
  • Basım Tarihi: 2004
  • Doi Numarası: 10.1021/jp037138z
  • Dergi Adı: Journal of Physical Chemistry A
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Sayfa Sayıları: ss.5990-6000
  • Marmara Üniversitesi Adresli: Hayır

Özet

In this paper, using DFT methods and reactivity indices, we show that the oxidative degradation of azo dyes occurs through the cleavage of the N-N bond following the hydroxyl radical addition to the chromophore. The geometries for two experimentally proposed reaction pathways regarding the cleavage of the C-N and N-N bonds for Cl- and CH3-substituted azo dye 4-(4′-sulfophenylazo)phenol are optimized at the B3LYP/6-31G(d) level of theory, and energies are further refined by single-point calculations at MPW1K/6-31+G-(d,p)//B3LYP/6-31G(d). Potential energy surfaces (PES) are compared for the two mechanisms to determine the energetically more favorable mechanism as well as to explain the huge reactivity difference between the Cl- and CH 3-substituted derivatives. Reactivity indices are used in the search for competing reactions.