This paper presents results of the analysis of organic coffee beans cultivated in Departamento del Cauca -Colombia. Beans studied are of the Coffea Arabica species cultivated in mountain soils of altitude close to 1500 m. Samples from green and roasted beans were characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and X-ray diffractometry (XRD). We intend to relate the features of the heating spectra with the transformation experimented by the coffee. Glass transition and phase transitions were examined. DSC and TGA spectra show that the green coffee experiments a high and fast decomposition after 200°C until 289°C with a remarkable transformation in a close range around 210°C. XRD shows significant changes for green and roasted beans associated to the amount of caffeine hydrates and caffeine anhydrous. Fit of XRD curves by Lorentzian shows a considerable increase of the active crystalline phase at 2θ equal to 20.4 0 for the roasted coffee. The results obtained from this study contribute to the insight associated with the final quality of coffee dependent on roasting methods. Better quality of coffee requires a refined and very controlled roasting process around of 218°C with a slow thermal treatment since the room temperature until the 200°C.
T h e preparation of 2-amino-5-nitrothiophene, Z-formamido-5-nitrothiophene, 2-acetamido-5nitrothiophene and 2-t-butyloxycarbonylarnino-5-nitrothiophene are described. Abnormal values of the coupling constants J3,4 had been observed in the 'H-nmr spectra of compounds obtained. J. Heterocyclic Chem., 18, 851 (1981).Aminothiophenes have become important intermediates for the synthesis of condensed thiophene derivatives. In connection with a general program directed to the study of such systems, we have prepared 2-amino-5-nitrothiophene (1). It is known that 2-aminothiophenes tend to be unstable in the absence of electron-withdrawing groups in the 3or 5-position. However, 2-amino-5-nitrothiophene (1) has not been previously described in the literature. In the present work we wish to report the preparation and the nmr spectra of 1 and related compounds.Of the different synthetic methods for the preparation of 2-aminothiophenes (l), the rearrangement of acyl azides to formamido derivatives is a widely used method. Thus, we attempted the synthesis of compound 1 from the acyl azide 2 as a precursor (cf. Scheme 1).Compound 2 was prepared from the acid chloride 3 (2). By the action of sodium azide on compound 3, a yellow solid was obtained in almost quantitative yield. This product was identified as the acyl azide 2 (3).Scheme I 4 2 T The formamido derivative 4 was prepared according to the method of Stevenson and Johnson (4) by the reaction of compound 2 with formic acid. The formyl proton was readily identifiable in the nmr spectrum appearing as a doublet at 8.8 ppm. This splitting is due to the restricted rotation of the formyl group. The coupling constant showed a value of 1.5 Hz (5). Several methods for cleaving the formyl group in 4 were tested (6). Under mild conditions 85 1 (dilute acid or alkali, room temperature) the formamido compound 4 was recovered unchanged. Under drastic conditions desulfurization resulted giving tarry products.In view of these results we tested the preparation of compound 1 from its t-butyloxycarbonyl derivative 5, according to Binder, et al., (7). By reaction of compound 2 with t-butyl alcohol in dry dioxane, compound 5 was obtained in 70% yield. When 5 was treated with anhydrous hydrogen bromide in an aprotic solvent (methylene chloride) a crystalline product was obtained. The melting point of this solid changed with time. This fact can be explained by the loss of hydrogen bromide from the salt (1 .HBr), due to the weak basicity of the amino compound 1. Drying this crystalline substance in a desiccator under vacuum with potassium hydroxide allowed us to isolate the free base 1. This product proved to be stable for 48 hours; after this time compound 1 darkens and polymerizes to a tar in contact with air. When it is stored under a vacuum or under a nitrogen atmosphere, the amine is stable for several days.By reaction of compound 1 with acetic anhydride, the N-acetyl derivative 6 was obtained in 60% yield (8). Spectral data and analyses were consistent with the structures of compounds 1 , 2...
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