Kinetics of oxidation of nicotinic and isonicotinic acids by permanganate in acidic medium

Department of Chemistry, University of Rajasthan, Jaipur-302 004, Rajasthan, India

E-mail : guptaks 14@rediffmail.com

Govt. College, Dausa. Rajasthan, India

Manuscript received 7 August 2008, revised 16 January 2009, accepted 11 February 2009

The most important feature of this study of the oxidation of nicotinic acid (Nic) and isonicotlnlc acid (lnic) by permanganate in acidic medium Is the complete solution of the rate laws (A) for Nic and (8) for lnic by varying [H+] over an extended concentration range.

-d[MnO₄-]/dt = {k₀ K₁ [H⁺] + k K₁ K₂ [H⁺]² + k₃ K₁ K₁ K₃ [H⁺]3}[MnO₄-]₁[Nic]₀/ {1+ K₁ [H⁺] + K₁ K₂ [H⁺]²}

-d[MnO₄-]/dt = {k K₂ [H⁺] + k₃ K₂ K₃ [H⁺]²} [MnO₄^-]_t [lnie]/(1 + K₂ [H⁺]}

The relationships of the rate parameters and their values are as follows : K₁(NC₅H₄COO^- + H⁺ ⇔ HN⁺C₅H₄COO^- [B]), 1.78 x 10⁴ (30") (Nic); K₁ (HN⁺C₅H₄CO^- [B] + H⁺ ⇔ HN⁺ C₅H₄COOH [C]), 46.2 (30°) (Nic), 33.6 (40°) (lnie); k₀ ([B) + MnO₄- → products), 1.56 x 10^-3 L mol^-1 S^-1 (30°) (Nic); k ([C) + MnO₄^-→ products), 1.64 x 10^-1 (30°) (Nic), 1.68 x 10^-1 L mol^-1 s^-1(40°) (lnic) and k₃ K₃ ([C) + HMnO₄ →. products), 2.02 x 10^-1 (30°) (Nic), 3.2 x 10^-3 L² mo1^-1 s^-1 (40°) (lnic). The reactivity of Nic was greater than that of lnic.