Kinetics of substitution of pyrazine mono-n-oxide and isoniazid on aquopentammineruthenium (II)

Abstract

The substitution of pyrazine mono-N-oxide in aquopentamineruthenium(II) presents the following kinetic parameters: k(25°C) = 3.0 × 102M−1 s−1, ΔH# = 16.4 kcal/mole−1, ΔS# = −10 cal K−1 mole−1. Up to 20% of the oxide is involved in parallel redox reaction. Isoniazid substitutes yielding a complex bound through the pyridinic nitrogen, by a path involving the neutral molecule, k(25°C) = 9.2 × 10−2 M−1 s−1, ΔH# = 16.6 kcal/mole−1, ΔS# = −7.7 cal.K−1.ole−1, and by an acid path, k(25°C) = 5 × 10−3 M−1 s−1. The two possible ( and Id) mechanisms for substitution in Ru(NH3)5H2O2+ are discussed.