9 research outputs found
Determination and Correlation of Solubility of Cefradine Form I in Five Pure Solvents from (283.15 to 308.15) K
The
solubility of cefradine form I in five pure solvents from (283.15
to 308.15) K was experimentally determined by using an equilibrium
method. It was found that the solubility of cefradine form I in all
tested solvents increased with the increase of temperature. Four thermodynamic
models were used to correlate the experimental solubility data. The
infinite-dilution activity coefficient and mixing properties including
the mixing free Gibbs energy, enthalpy, and entropy of cefradine form
I solution were also calculated by using the nonrandom two-liquid
(NRTL) model. It was found that the correlated results by the van’t
Hoff equation, the modified Apelblat equation, and the NRTL model
agreed well with the experimental data
Experimental Determination and Computational Prediction of Androstenedione Solubility in Alcohol + Water Mixtures
This
article evaluates the accuracy and applicability of three
of the most common solubility models (i.e., Jouyban–Acree,
NRTL-SAC, and COSMO-RS) in prediction of androstenedione (AD) solubility
in binary mixtures of methanol + water and ethanol + water. The solubilities
were measured from (275 to 325) K using medium-throughput experiments
and then well represented mathematically by modified Apelblat and
CNIBS/Redlich–Kister equations. The computational results show
that AD solubility decreases monotonically with increasing water concentration
in methanol + water mixtures, but it has a maximum at 0.15–0.30
mole fraction of water in the ethanol aqueous solution. Moreover,
the performance of three solubility prediction models in this particular
case was compared to identify the advantages and disadvantages of
each model. The overall average relative deviation (ARD) for solubility
prediction is 4.4% using Jouyban–Acree model, while it is 18.3%
with NRTL-SAC model. Surprisingly, COSMO-RS model in combination with
reference solubility achieves a good performance for solubility prediction
in mixed solvents, including the prediction of synergistic effect
of solvents, with overall ARD of only 4.9%
Flexible Optical Waveguides in Heterocyclic Schiff Base Self-Assembled Hydrogen-Bonded Solvates
Flexible fluorescent crystalline materials exhibit both
mechanical
and optical properties and have received great attention due to their
potential applications in flexible optical devices. Simultaneously
adjusting the mechanical and optical properties of crystalline materials
remains interesting and challenging. In the present work, a guest
molecule was introduced via hydrogen-bonded solvation, which achieved
excellent mechanical elasticity and higher fluorescence emission than
that of the host heterocyclic Schiff base molecule crystal itself.
The crystal structure–property relationship and the molecular
mechanism of the elasticity were then investigated in detail. It revealed
that solvent molecules play a key role in changing both the stacking
of fluorescent molecules and the interaction energy framework. In
addition, the flexible fluorescent solvate exhibits a good waveguide
property. A bent crystal was found to have a larger optical loss coefficient
than a straight crystal. Furthermore, the size effect on the optical
loss coefficient of the waveguide was discussed in which the optical
loss coefficient decreases as the sizes increase. Such a size effect
is usually neglected in waveguide material research and should be
complemented in the performance evaluation of optical waveguides
Flexible Optical Waveguides in Heterocyclic Schiff Base Self-Assembled Hydrogen-Bonded Solvates
Flexible fluorescent crystalline materials exhibit both
mechanical
and optical properties and have received great attention due to their
potential applications in flexible optical devices. Simultaneously
adjusting the mechanical and optical properties of crystalline materials
remains interesting and challenging. In the present work, a guest
molecule was introduced via hydrogen-bonded solvation, which achieved
excellent mechanical elasticity and higher fluorescence emission than
that of the host heterocyclic Schiff base molecule crystal itself.
The crystal structure–property relationship and the molecular
mechanism of the elasticity were then investigated in detail. It revealed
that solvent molecules play a key role in changing both the stacking
of fluorescent molecules and the interaction energy framework. In
addition, the flexible fluorescent solvate exhibits a good waveguide
property. A bent crystal was found to have a larger optical loss coefficient
than a straight crystal. Furthermore, the size effect on the optical
loss coefficient of the waveguide was discussed in which the optical
loss coefficient decreases as the sizes increase. Such a size effect
is usually neglected in waveguide material research and should be
complemented in the performance evaluation of optical waveguides
Solution-Mediated Polymorphic Transformation of Prasugrel Hydrochloride from Form II to Form I
In situ Raman spectroscopy
was applied for the analysis of the
solution-mediated polymorphic transformation of prasugrel hydrochloride
from the metastable form II to the stable form I. The solution concentration
during the transition process was monitored by a gravimetric method.
The main factors studied were solvent, temperature, solid loading,
and agitation speed. Because of the balance between the solubility
and the strength of solute–solvent interactions, the transformation
rate was highest in ethyl acetate and lowest in butanone at all three
temperatures studied (20, 30, and 40 °C). The thermodynamic driving
force of the polymorphic transformation from form II to form I was
evaluated through solubility measurements of the two forms in ethyl
acetate, acetone, and butanone. At increasing temperature, the nucleation
induction time and the overall transformation time decreased despite
the decreasing driving force. The solid loading seemed to have no
effect on the transformation time because of surface nucleation of
form I on form II, as determined from the morphology–time profile
through polarizing microscope analysis, whereas increasing the agitation
rate resulted in a faster polymorphic transformation process. It was
confirmed by transformation experiments that the polymorphic transformation
from form II to form I is controlled by the nucleation and growth
of the stable form I crystal
Solid–Liquid Phase Equilibria of Ternary Mixtures Containing 1,2‑Dihydroacenaphthylene and Dibenzofuran
Ternary
phase diagram data of 1,2-dihydroacenaphthylene-dibenzofuran
mixtures in a series of alcohols, including methanol, ethanol, propan-2-ol,
propan-1-ol, butan-1-ol, and pentan-1-ol were measured using a dynamic
method at 308.15 and 313.15 K. The experimental data were correlated
with the Wilson model (including pseudobinary systems), UNIQUAC model,
and NRTL model. The results indicate that pseudobinary systems with
the Wilson equation give a better description of the solubility of
the ternary system. The eutectic point shifts toward dibenzofuran
when the more polar methanol and ethanol are used. This shift may
help achieve a more efficient separation of 1,2-dihydroacenaphthylene
and dibenzofuran
Concomitant Polymorphism of Prasugrel Hydrochloride in Reactive Crystallization
Concomitant
polymorphism of prasugrel hydrochloride was investigated in reactive
batch crystallization experiments at 20 and 40 °C. The solubility
of prasugrel hydrochloride form I and form II was experimentally determined.
To understand the effects of reaction kinetics, supersaturation ratio,
and nucleation kinetics on the behavior of concomitant polymorphism
of prasugrel hydrochloride and the solvent-mediated transformation
process, online techniques such as attenuated transform reflectance
Fourier transform infrared (ATR-FTIR) spectroscopy, Raman spectroscopy,
and focused beam reflectance measurement (FBRM) were used to in situ
monitor the reactive crystallization of prasugrel hydrochloride. It
was found that prasugrel and hydrochloric acid react promptly and
the designed supersaturation can be established almost instantly.
The interfacial energies and thus relative nucleation rates of prasugrel
hydrochloride form I and form II were calculated, and it was concluded
that, at all investigated supersaturations, the nucleation rate of
form II is always higher than the nucleation rate of form I. At lower
supersaturation, thermodynamics dominated the crystallization process
and form I was obtained, while at higher supersaturation, kinetics
was critical in the crystallization process and form II was produced.
At moderate supersaturation, both thermodynamics and kinetics played
important roles and concomitant polymorphism of form I and form II
was observed. Solvent-mediated transformation experiments were performed
with and without seeding. It turns out that the transformation cannot
happen without seeding of form I. Therefore, not reaction kinetics
and polymorphic transformation but the concomitant nucleation should
be the inherent reason for the observed concomitant polymorphism
Preparation and Dehydration Kinetics of Complex Sulfadiazine Calcium Hydrate with Both Channel-Type and Coordinated Water
A new
hydrate of sulfadiazine calcium (Hydrate I) was discovered,
and the crystal structure was determined using single crystal X-ray
diffraction. Both channel-type water (9.23 wt %) and calcium-ion coordinated
water (11.87 wt %) existed in the unit cell. The thermal stability
and dehydration of Hydrate I were investigated by thermal gravimetric
analysis, hot stage microscopy, powder X-ray diffraction, Fourier
transform infrared spectroscopy, and scanning electron microscopy.
A two-step dehydration process was detected from Hydrate I to anhydrous
phase (AP) with the intermediate of the less-hydrated form (Hydrate
II). The dehydration kinetics of Hydrate I with both channel-type
and coordinated water was studied using model fitting method and model
free method in isothermal mode. The dehydration activation energy
was derived via the Friedman method. Further, the first-step dehydration
of Hydrate I was determined to be the 2D phase boundary reaction mechanism,
and the second-step dehydration was found to be 3D phase boundary
reaction mechanism via model fitting approach
Preparation and Dehydration Kinetics of Complex Sulfadiazine Calcium Hydrate with Both Channel-Type and Coordinated Water
A new
hydrate of sulfadiazine calcium (Hydrate I) was discovered,
and the crystal structure was determined using single crystal X-ray
diffraction. Both channel-type water (9.23 wt %) and calcium-ion coordinated
water (11.87 wt %) existed in the unit cell. The thermal stability
and dehydration of Hydrate I were investigated by thermal gravimetric
analysis, hot stage microscopy, powder X-ray diffraction, Fourier
transform infrared spectroscopy, and scanning electron microscopy.
A two-step dehydration process was detected from Hydrate I to anhydrous
phase (AP) with the intermediate of the less-hydrated form (Hydrate
II). The dehydration kinetics of Hydrate I with both channel-type
and coordinated water was studied using model fitting method and model
free method in isothermal mode. The dehydration activation energy
was derived via the Friedman method. Further, the first-step dehydration
of Hydrate I was determined to be the 2D phase boundary reaction mechanism,
and the second-step dehydration was found to be 3D phase boundary
reaction mechanism via model fitting approach