Influence of History of Solution in Crystal Nucleation of Fenoxycarb: Kinetics and Mechanisms

Abstract

Nearly 1800 induction time experiments have been performed on crystal nucleation of fenoxycarb in isopropanol to investigate the influence of solution pretreatment. For each preheating temperature and preheating time, at least 80 experiments were performed to obtain statistically valid results. The relationship between the inverse of the induction time and the preheating time can be reasonably described as an exponential decay having time constants ranging up to days depending on the temperature. This dependence on the preheating temperature corresponds to an activation energy of over 200 kJ/mol. Given sufficiently long preheating time and high temperature, the solution appears to reach a steady-state where the "memory" effect has disappeared. Density functional theory modelling suggests that the molecular packing in the crystal lattice is not the thermodynamically stable configuration at the level of simple dimers in solution, while modelling of the first solvation shell reveals that solute aggregation must exist in solution due to the low solvent to solute molecular ratio. It is thus hypothesized that the dissolution of crystalline material at first leaves molecular assemblies in solution that retain features of the crystalline structure which facilitates subsequent nucleation. However, the longer the solution is kept at a temperature above the saturation temperature and the higher the temperature, the more these assemblies disintegrate, and transform into molecular structures less suited to form critical nuclei..

Conundrum of γ glycine nucleation revisited: to stir or not to stir?

“…We note that in this work glycine solutions were prepared at 90°C in order to access higher supersaturations, and that thermal history of solutions could play a role in both nucleation kinetics and polymorphic outcomes. 39,40 Our results, showing a preference for γ over α at higher supersaturations, are in agreement with observations from evaporating droplets. 31 This shows that both α and γ nucleate under quiescent conditions at concentrations and temperatures investigated.…”

Recovery of Scandium by Crystallization Techniques

“…When a solution is cooled to supersaturation resulting in nucleation, the thermal treatment, that is, the heating temperature and duration that the solution undergoes during dissolution of crystals has an effect on the metastable zone width, induction time, hence nucleation upon cooling the same solution again. In general, it was hypothesized that during the initial dissolution phase of crystals, the solution retains some molecular assemblies that promote nuclei formation at a reduced supersaturation [34,35]. A similar phenomenon could have occurred upon filtration and washing of the solid product resulting in molecular assemblies passing through the membrane filter into the solution that was cooled to lower temperatures in subsequent experiments.…”

Solute clustering in undersaturated solutions – systematic dependence on time, temperature and concentration

“…fenofibrate. Solid-liquid thermodynamic properties and the solubility in five pure organic solvents, 22 a crystal shape and structure analysis, 23 and data on its nucleation behaviour 24 has been reported. Primary nucleation of fenoxycarb in isopropanol solution has been shown to exhibit a strong effect of pre-heating on the propensity for nucleation, with increased temperature and time of pre-treatment of the solution resulting in longer nucleation induction times.…”

“…Primary nucleation of fenoxycarb in isopropanol solution has been shown to exhibit a strong effect of pre-heating on the propensity for nucleation, with increased temperature and time of pre-treatment of the solution resulting in longer nucleation induction times. 24 The time scale for the process of erasure of this ''history of solution'' effect has been shown to be surprisingly large; of the order of hours or even days. Contrary to most compounds featured in clustering studies to date, the fenoxycarb molecule is bigger and has a significant degree of conformational flexibility.…”