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The solubility of 2-chloro-N-(4-methylphenyl)propanamide (S1) in ethyl acetate + hexane mixtures between the temperatures of 273.43 to 327.67 K, in toluene + hexane mixtures from 273.24 to 331.62 K, in acetone + hexane mixtures from 269.81 to 318.8 butanone + hexane mixtures between 267.10 and 322.92 were determined using the polythermal method. In situ focused beam reflectance measurement (FBRM) was used to characterize the dissolution properties and to provide S1's saturation temperature profile as a function of concentration. It was demonstrated that the solubility of S1 increases with increasing temperature at constant solvent composition. The experimental solubility data were correlated using Apelblat, λh, and phase equilibria with NRTL (nonrandom two liquid) model equations, and the predicted solubility data obtained agree sufficiently with the experimental data based on the relative deviation (RD%) and average relative deviation (ARD%) values. The Apelblat and λh model equation provides a convenient operational model of engineering interest to calculate the solubility of S1 quickly and easily, although it does not take the solvent composition into account, therefore needing separate parameters for each different solvent compositions. Therefore, the phase equilibria with NRTL model equation is used to provide a more comprehensive model that illustrates the effect of solvent composition on the solubility more apparently. One general set of NRTL parameters has the capability of describing all solvent compositions. Additionally, the melting temperature, T m and the molar fusion enthalpy, Δ fus H, (394.83 K and 26.77 kJ mol −1 respectively) of S1 were determined by differential scanning calorimetry (DSC).

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Abstract:The hazardous diazo transfer reagent mesyl azide has been safely generated and used in situ for continuous diazo transfer as part of an integrated synthetic process with an embedded safety quench. Diazo transfer to -keto esters and a -

This paper presents a laboratory study examining the dissolution kinetics of ibuprofen crystals in water containing a phosphate buffer (pH 7.20) at 37 °C, examining the influences of initial undersaturation ratio, agitation rate, crystal habit, and particle size. For each experiment, the concentration during the dissolution process was followed using UV spectroscopy, ATR-FTIR, and FBRM methods. The dissolution profiles were correlated using eight mathematical models, and the dissolution rate parameters were determined. The Weibull model, the Korsmeyer−Peppas model, and the first-order kinetics model gave better correlation results than the other models used in this paper for the dissolution of ibuprofen crystals. The particle size distribution slightly shifted to the right after dissolution, confirming that smaller particles with higher surface areas dissolved more rapidly. During dissolution, two distinct behaviors were obtained at different levels of undersaturation ratio; therefore, it is postulated that the mechanism of dissolution switches from being mass-transfer-limited at higher levels of undersaturation ratio to being limited by the rate of surface detachment at lower undersaturation ratio levels.