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  • Author or Editor: M. Leităo x
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Abstract  

Enthalpies of solution of various terfenadine samples in methanol and in ethanol were measured. Samples were prepared by crystallization in different solvents. The calorimetric results give important information on crystal structure of the terfenadine forms and on the solute/solvent interactions of this compound with the solvents.

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Abstract  

The study of trans- and cis-1,2-cyclohexanediol by infrared spectroscopy was performed. The variation of the maximum frequency and of the bandwidth of the OH stretching vibration give evidence of the role played by hydrogen bonding in the solid and liquid phases of both isomers and allows to follow the phase transitions. A solid rotator phase is shown for the cis compound.

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Abstract  

Several samples of terfenadine prepared by crystallization from different solvents under different experimental conditions were studied. The DSC curves obtained at a heating rate of 1C min−1 afforded the temperature of melting and the mole fractions of the components of each sample. Certain of the samples were composed of two solid phases mixed in molar ratios varying between nearly one and a single structural form. Three polymorphic forms were identified.

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Abstract  

Terfenadine samples prepared by crystallization in different media and supersaturation conditions were used to investigate the polymorphism of the substance. The study was based on DSC melting curves. An empirical parametric equation was used for modelling the experimental data. The signal recorded was resolved into the corresponding overlapping peak components by fitting analysis. Four polymorphic phases were identified.

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Abstract  

In this paper the structural characterization of terfenadine crystallized from ethanol-water, ethanol and methanol is performed by infrared spectroscopy. The OH stretching vibration, composed of three markedly overlapped bands, is analyzed by peak fitting. The assignment of the hydrogen bonds was conducted making use of band parameters, spectroscopic data for CCl4 solutions, and molecular dynamics calculations from dimeric systems. Terfenadine just precipitated from solvents is never in the highest crystalline state. This state is reached when the samples are heated at a temperature above 100C. Some amorphous solid is coprecipitated with the crystalline phase, particularly in methanol.

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