Propriedades vibracionais do ácido esteárico e palmítico

Abstract

In this work, stearic and palmitic acids were characterized in Bm and C forms, at room temperature, through Infrared and Raman spectroscopy. First, crystallization of the two fatty acids was obtained using the method of slow evaporation of solvent using two solvents, chloroform and ethanol, at two different temperatures: ~ 16 °C e ~ 0 °C. Single crystals were obtained in two polymorphic forms called in the scientific literature Bm and C in both monoclinic symmetry with space group P21/a (C2h5) and Z=4, which were confirmed by technique of X-rays diffraction. Then spectroscopic techniques were applied to characterize the acids. Infrared measurements in the mid-infrared region, between 400 to 3000 cm-1, were performed and Raman in the region 30 to 3000 cm-1. This allowed the characterization of stearic and palmitic acids. The Infrared and Raman spectra of the two polymorphic forms at the two acids mainly showed differences in the intensity and position of the peaks. The assignment of the observed bands was made by correlation with Raman and Infrared spectra of its individual components and other compounds found in the literature.