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Effect of the ionic strength on the redox reaction of dicyanobis(bipyridine)iron(III)‐iodide in binary and ternary solvent systems
Author(s) -
Khattak Rozina,
Khan Muhammad Sufaid,
Ullah Rizwan,
Ali Mahnoor,
Rahman Wajeeha,
Hakeem Faryal,
Ayaz Kainat,
Bibi Zainab
Publication year - 2021
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.21419
Subject(s) - chemistry , ionic strength , reaction rate constant , iodide , 2,2' bipyridine , ternary operation , bipyridine , inorganic chemistry , redox , reaction rate , kinetics , aqueous solution , crystallography , organic chemistry , catalysis , crystal structure , physics , quantum mechanics , computer science , programming language
The redox reaction between dicyanobis(bipyridine)iron(III) and iodide ion follows first‐order kinetics in 10% (v/v) tertiary butyl alcohol‐water. The reaction was found first and zero order in iodide and dicyanobis(bipyridine)iron(III), respectively, at 0.06 M ionic strength and 293 ± 1 K. The thermodynamic parameters of activation such as E A (16.07 kJ mol −1 ), A (1 × 10 −4 M s −1 ), Δ H # (13.6 kJ mol −1 ), Δ S # (−329.81 J K −1 mol −1 ), and Δ G # (90.1 kJ mol −1 ) were determined. The effect of the ionic strength on the rate constant leads to recognizing the stabilization or destabilization of the transition state complex that forms during the rate‐determining step of the reaction. The value of the zero‐order rate constant was decreased with increasing ionic strength that yielded a negative value of the slope in each binary and ternary solvent systems. This negative sign refers to the electron transfer between opposite charge carriers such as [Fe III (bpy) 2 (CN) 2 ] + and I − during the rate‐determining step. The destabilization of the transition state complex is surfaced by the increasing slope, that is, 5 < 10 < 15% (v/v) tertiary butyl alcohol‐water with a gradual decrease in the rate constant. However, its stability emerges by relatively small values of the slope in 17.5 < 25 ≤ 30% (v/v) tertiary butyl alcohol‐water and 8:2:90 < 6:4:90% (v/v) dioxane: tertiary butyl alcohol: water with reasonably fast rate of reaction.