Is Water Electron Withdrawing or Electron Donating: Acid-Base Properties of Different Water Related Species Treated by Taft Equation

V. Jagannadham^1, , Sanjeev Rachuru² and D. A. Padmavathi¹

¹Department of Chemistry, Osmania University, Hyderabad-500007, India

²Department of Chemistry, St. Ann's College for Women, Mehdipatnam Hyderabad-500028, India

Cite this paper:
V. Jagannadham, Sanjeev Rachuru and D. A. Padmavathi. Is Water Electron Withdrawing or Electron Donating: Acid-Base Properties of Different Water Related Species Treated by Taft Equation. World Journal of Chemical Education. 2026; 14(3):47-50. doi: 10.12691/wjce-14-3-2

Abstract

Water (HOH), hydroxyl radical (HO•), hydroxide ion (HO−), hydrogen peroxide (HHO₂), hydroperoxyl radical HO₂• hydroperoxide anion HO₂− and hydronium ion (HH₂O⁺) are all water related species and are environmentally important. The corresponding acid -base couples are represented as HOH/OH−, HO•/O•−, HO−/O²−, HHO₂/, HO₂•/ O₂•^-, HO₂−/ O₂²− and H₃O⁺/H₂O. Therefore, the corresponding conjugate bases are hydroxide ion OH−, mono oxygen radical anion O•−, oxide dianion O²−, hydroperoxide anion HO₂−, peroxyl radical anion O₂•^-, peroxide dianion O₂²− and H₂O respectively. The acid-base properties are well characterized by treating the pKa data with Taft σ* values of the corresponding conjugate bases of these couples using Taft linear free-energy relationship (LFER). Positive Taft ρ* value of 17.7 indicates that electron withdrawing species facilitate the deprotonation and vice-versa. The present study is a good class-room exercise for both undergraduate and graduate advanced physical-organic chemistry level.

Keywords:
Species of water Taft equation

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