Browsing by Author "Caldin, E. F."

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Kinetics and Thermodynamics of the Complex-formation of Nickel(II) and Cobalt(II) Ions with Ammonia and Pyridine- 2-azodimethylaniline in Water, at Pressures from 1 bar to 2 kbar
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1972, 68 (12), 1972) Caldin, E. F.; Grant, M. W.; Hasinoff, B. B.
    Thermodynamic and kinetic measurements have been made at a series of pressures from 1 bar to 2 kbar on the reactions of nickel(IQ and cobalt(II) ions with ammonia and with the large bidentate ligand PADA (pyridine-2-azodimethylaniline) in aqueous solution. The apparatus consisted of a high-pressure cell and a laser temperature-jump apparatus with spectrophotometric detection. A method is described for determining equilibrium constants at high pressures from the amplitude of the optical-density change on reaction. The values found for AK* are all in the region of 4-5 to + 8 cm3 mol-1. The results are consistent with the interpretation that the transition state involves considerable stretching of the cation-water bond, as postulated in the Eigen-Wilkins mechanism.
  • No Thumbnail Available
    Item
    Kinetics and Thermodynamics of the Formation of the Donor Acceptor Complex of Tetracyanoethylene with Hexamethyl benzene in Solution, by a Microwave Temperature-jump method
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1972, 68 (5), 1972) Caldin, E. F.; Crooks, J. E.; O’Donnell, D.; Smith, D.; Toner, S.
    The rate of formation of the donor-acceptor complex between tetracyanoethylene and hexamethylbenzene, in 1-chlorobutane as solvent, has been measured at –83°C by a temperature-jump method using microwave heating. Equilibrium constants have also been determined over a range of temperature. The rate constant is (1.45 ± 0.3)× 108 l. mol–1 s–1(the uncertainty referring to the estimated limits of error). This is smaller by an order of magnitude than the calculated value for a diffusion-controlled reaction. The reason for this is discussed and it is concluded that there is possibly an energy barrier due to solvation changes. The rate constant in a solvent consisting of chlorobenzene + n-heptane (40–60 v-v) has also been determined, allowance being made for the parallel complex-formation between chlorobenzene and tetracyanoethylene; at –60°C, it was found to be (8 ± 3)× 108 l. mol–1 s–1.