RESUMO
Active functional groups in biofilms determine the adsorption and desorption of contaminants and nutrients. Epilithic biofilms were characterized in order to understand the association between the chemistry alteration patterns and the surrounding anthropic activities of the Guaporé River watershed. The instrumental analyses included pyrolysis coupled to gas chromatography and mass spectroscopy, spectroscopy in the IR region with attenuated total reflectance, and two-dimensional nuclear magnetic resonance. Spectrometric techniques demonstrated that epilithic biofilms are mainly composed of polysaccharides, nitrogen-containing compounds, lipids, and aromatic and phenolic structures, which have functional groups characteristic of alcohols, esters, ethers, and amides. The polysaccharide levels reflect well the environmental pressures. The chemical composition of epilithic biofilms can be an effective tool for environmental assessment in watercourses, since the different anthropic actions developed in watersheds, mainly agriculture and urban areas, can modify the organic fraction of biofilms.
Assuntos
Agricultura , Rios , Biofilmes , Brasil , Monitoramento Ambiental , Cromatografia Gasosa-Espectrometria de MassasRESUMO
Chiral nonracemic aminated nitroso acetals were synthesized via diastereoselective multicomponent [4 + 2]/[3 + 2] cycloadditions employing new (S,E)-γ-nitrogenated nitroalkenes 5a-c as heterodienes, ethyl vinyl ether (EVE) as a dienophile, and selected electron-deficient alkenes as 1,3-dipolarophiles. The employment of different organic solutions of LiClO4 or LiCl as promoter systems provided the respective nitroso acetals with yields from 34-72% and good levels of diastereoselectivity. In addition, the nitroso acetal 9c was transformed to the pyrrolizidin-3-one derivative 14c, proving the usefulness of the route in the synthesis of an interesting chiral compound. The elucidation of the stereostructures was based on 2D COSY, NOESY and HSQC NMR experiments as well as an X-ray diffraction experiment.
RESUMO
The title compound, [Au(C(10)H(9)N(4)O(2)S)(C(18)H(15)P)], is nearly linear at Au(I), with Au-N = 2.0707 (18) A, Au-P = 2.2310 (8) A and N-Au-P 171.93 (5) degrees. The molecules are linked by intermolecular N-H...O bonds.
RESUMO
The title compound, C(20)H(14)Te(2), shows a transoid conformation, with a C[bond]T[bond]-[bond]Te[bond]C torsion angle of 97.96 (9) degrees. The Te[bond]Te units show approximate eta(6) interactions with neighbouring naphthyl groups, forming chains along the c axis. The molecule lies about a crystallographic twofold axis.