Iron (II) and iron (III) isotope exchange in water–dimethyl sulfoxide mixtures

✍ Scribed by Marian S. Henry; Warren L. Reynolds

• Book ID: 102926292
• Publisher: John Wiley and Sons
• Year: 1972
• Tongue: English
• Weight: 597 KB
• Volume: 4
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.550040103

✦ Synopsis

The rate of the isotope exchange reaction between iron(I1) and iron(II1) perchlorates has been measured in a solvent mixture containing a 3 : 2 mole ratio of water to dimethyl sulfoxide over the temperature range from 25" to -98°C. I n this temperature range, the reactants can diffuse together faster than they can undergo isotope exchange. The activation enthalpy and entropy for the acid-independent reaction were 6.0 f 1.2 kcal/mole and -38 i 17 cal/deg mole, respectively. Below -22"C, the acid-dependent exchange reaction did not contribute significantly to the exchange. I n liquid media at -112' and -1 17°C and in a solid glass at -136OC, no isotope exchange was observed over the period of a calculated half-life for the reaction. At these temperatures, the rate at which the reactants diffuse together is slower than the calculated rate of isotope exchange. In a solid glass at -196°C ,no isotope exchange was observed over the period of one week.