Effect of cosolvent on the volume of activation for base hydrolysis of tris(1.10-phenanthroline)- and tris (2.2′-bipyridine)iron(II) complexes
✍ Scribed by John Burgess; Colin D. Hubbard
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 137 KB
- Volume
- 32
- Category
- Article
- ISSN
- 0538-8066
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✦ Synopsis
The kinetics of the base hydrolysis of Fe(phen) 3 2ϩ and Fe(bipy) 3 2ϩ (phen ϭ 1,10phenanthroline and bipy ϭ 2,2'-bipyridine) in some aqueous alcohol mixtures at ambient and elevated pressures (up to 1kbar) have been monitored spectrophotometrically at 25.0ЊC. For a given pressure, the alcohol cosolvent increases the rate of reaction relative to the reaction in a wholly aqueous medium. In all cases, increasing pressure causes rate retardation and derived volumes of activation for the reactions in aqueous solvent mixtures vary between ϩ15 and ϩ25 cm 3 mol Ϫ1 , indicating that solvation changes of a different magnitude occur upon reaching the transition state from those occurring for the reactions in aqueous medium. Since the reaction has been established earlier to be nucleophilic attack of the incoming hydroxide ion, the volumes of activation signify marked increases in the loss of electrostricted solvent from the vicinities of the hydroxide ion and the iron(II) complex ions.