Kinetics and thermodynamics of heat conduction microcalorimetry

Abstract

Heat conduction microcalorimetry offers an important technique in the context of physical organic chemistry for the study of chemical reactions in solution. The thermodynamic basis of the technique is discussed. Model reaction schemes are used in an examination of the dependence on time of the rate of heat production. The impact of rate constants and enthalpies of reaction on the recorded dependence is reviewed for first-and second-order reactions.

Synthesis of Enantiomerically Pure 4-Hydroxy-2-cyclopentenones

“…The pseudo-first-order rate constants, k obsd , determined from the values of conversion versus residence time gave the values of 0.094, 0.268, 0.906, and 4.87 min –1 at 150, 175, 200, and 240 °C, respectively, and provided the activation parameters Δ H ⧧ = 18 ± 1.4 kcal/mol and Δ S ⧧ = −38 ± 3 cal/mol/K. These values are in accordance with those generally observed for unimolecular reactions in water near neutral pH. − …”

Study of Kinetics of Bromophenol Blue Fading in Alcohol-Water Binary Mixtures by SESMORTAC Model

“…This results in an increased negative entropy of formation accompanying a more restricted number of configurations and makes these polymeric species more susceptible to thermal depolymerization, 23,24 Figure 2. If ∆H ≠ is split into a reaction and a solvation component, 27 it is reasonable to expect that solvent ----------------------------------------------------------------------------------- ---------------------------------------------------------------------------------- structural perturbations causing hydrogen-bond formation or breakage will affect the solvation component of ∆H ≠ , as this effect in the bulk phase will be passed on to the reaction site via the solvation shells of the transition and initial states. 20 By comparison of the rate constants in Tables 10-15, we can see at the same mole fractions and temperatures, the following relation holds for:…”

“…As adding water to solvent mixture would increase the reaction rate, mechanism of BPB fading may be outlined in the form: (26) where alcohol molecules are shown by S and k 1 , k −1 and k 2 are fundamental rate constants of BPB fading reaction in aqueous alcohol solutions. Assuming that a steady-state concentration of ACSM is attained in the mixed solvent, we have: (27) and the rate equation is (28) by substituting (27)…”