title: Calorimetric determination of rate constants and enthalpy changes for zero-order reactions.
abstract: Calorimetry is a general method for determination of the rates of zero-order processes, but analysis of the data for the rate constant and reaction enthalpy is difficult because these occur as a product in the rate equation so evaluation of one requires knowledge of the other. Three methods for evaluation of both parameters, without prior knowledge, are illustrated with examples and compared with literature data. Method 1 requires the reaction to be studied in two buffers with different enthalpies of ionization. Method 2 is based on calculation of reaction enthalpy from group additivity functions. Method 3 applies when reaction progresses to completion. The methods are applied to the enzymatic hydrolysis of urea, the hydrolysis of acetylsalicylic acid, and the photodegradation of nifedipine, respectively.
authors.affiliation: UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London, WC1N 1AX, UK.
authors.forename: Luis
authors.initials: L
authors.lastname: Almeida e Sousa
authors.forename: Anthony E
authors.initials: AE
authors.lastname: Beezer
authors.forename: Lee D
authors.initials: LD
authors.lastname: Hansen
authors.forename: David
authors.initials: D
authors.lastname: Clapham
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Connor
authors.forename: Simon
authors.initials: S
authors.lastname: Gaisford
mesh_terms: D001241:Aspirin / Q000737:chemistry / Q000378:metabolism*; D002151:Calorimetry; D006868:Hydrolysis; D009543:Nifedipine / Q000737:chemistry*; D055668:Photochemical Processes; D013816:Thermodynamics; D014508:Urea / Q000737:chemistry / Q000378:metabolism*; D014510:Urease / Q000737:chemistry / Q000378:metabolism*
chemical_list: D014508:Urea; D014510:Urease; D009543:Nifedipine; D001241:Aspirin