Benedito S. Lima-Neto

Carbamato de etila em bebidas alcoólicas (cachaça, tiquira, uísque e grapa)

The presence of ethyl carbamate in cachacas, tiquiras, whiskies and grapes was investigated by GC-MS, monitoring the m/z 62 ion. The external standard method was used for quantitation in 188 samples (126 cachacas, 37 tiquiras, 6 grappas and 19 whiskies). The results of the study for cachaca were analysed considering the geographic origin, distillation type (still or column), bottle coloration (amber or transparent) and ageing. The average contents of ethyl carbamate in cachacas and tiquiras were 0.77 and 2.4 mg L-1, respectively. These values were higher than the mean concentration found in grapes (0.045 mg L-1) and whiskies (0.14 mg L-1). On average the cachacas distilled in column tend to present higher values of ethyl carbamate than those from still. In the sampling studied it was not possible to define a correlation between content of ethyl carbamate, bottle coloration and ageing time.

Comparison between Cachaça and Rum Using Pattern Recognition Methods

The differentiation between cachaça and rum using analytical data referred to alcohols (methanol, propanol, isobutanol, and isopentanol), acetaldehyde, ethyl acetate, organic acids (octanoic acid, decanoic acid, and dodecanoic acid), metals (Al, Ca, Co, Cu, Cr, Fe, Mg, Mn, Ni, Na, and Zn), and polyphenols (protocatechuic acid, sinapaldehyde, syringaldehyde, ellagic acid, syringic acid, gallic acid, (-)-epicatechin, vanillic acid, vanillin, p-coumaric acid, coniferaldehyde, coniferyl alcohol, kaempferol, and quercetin) is described. The organic and metal analyte contents were determined in 18 cachaça and 21 rum samples using chromatographic methods (GC-MS, GC-FID, and HPLC-UV-vis) and inductively coupled plasma atomic emission spectrometry, respectively. The analytical data of the above compounds, when treated by principal component analysis, hierarchical cluster analysis, discriminant analysis, and K-nearest neighbor analysis, provide a very good discrimination between the two classes of beverages.

Influência do material do destilador na composição química das aguardentes de cana: parte II

The quantitative chemical analysis of the Brazilian sugar cane spirit distilled from glass column packaged with copper, stainless steel, aluminum sponge, or porcelain balls is described. The main chemical compounds determined by gas chromatography coupled with flame ionization (FID) and flame photometric (FPD) detectors and liquid chromatography coupled with diode array detector are aldehydes, ketones, carboxylic acids, alcohols, esters and dimethylsulfite (DMS). The spirits produced either in columns filled with copper or aluminum pot still exhibits the lowest DMS contents but the higher sulfate and methanol contents, whereas spirits produced in stainless steel or porcelain showed higher DMS concentration and lower teors of sulfate ion and methanol. These observations are coherent with DMS oxidation to sulfate, with methanol as by product, in the presence of either copper or aluminum.

A rapid and sensitive method for dimethylsulphide analysis in Brazilian sugar cane sugar spirits and other distilled beverages

A purge and trap concentrator coupled to gas chromatography was used to quantify dimethylsulphide in distilled beverages. A very good performance was obtained using a HP-FFAP column and a mass selective detector operating in SIM mode (m/z 62): detection limit 8 x 10-9 mol L-1; good repeatability and total time of analysis 25 minutes. The method has been applied for sixty samples of alcoholic beverages (cachacas, tiquiras, grappas, whiskies, brandies, vodkas, rum and a tequila). The cachacas exhibit the highest content of dimethylsulphide (median 3.16 x 10-4 mol L-1), followed by grappa (median 1.45 x 10-4 mol L-1). The presence of dimethylsulphide was not observed in the samples of rum.

The ring size of cyclic amines as a relevant feature in the activity of Ru-based complexes for ROMP

The novel complex [RuCl2(PPh3)2(pyrrolidine)] exhibited a square pyramidal (SQP) type geometry, with the amine in the apical position and trans-positioned phosphines. There was activity observed for ROMP of norbornene (NBE) either under air or an inert atmosphere of argon at 25 °C. Saturation profile-fitting describes the curves of yields as a function of time (5–120 min) under either atmosphere. The results were sensitive to the solution volume in the range of 2–8 mL of CHCl3, mainly under air. Quantitative yields under argon for 120 min at any solution volume were obtained. The order of magnitude of 103–105 g mol−1 for Mw and PDI values ranging from 1.6 to 3.5 was measured by SEC. In most of the cases, the ratios of yields from the runs under argon and air were close to the unit, indicating an insignificant loss of reactivity of the active species in the presence of molecular oxygen from air. A parent complex with diethylamine, but with trigonal bipyramidal (TBP) type geometry, was inactive for ROMP. The activity in these types of complexes was compared with that of already reported Ru-amine-based complexes in terms of electronic effects, with an additional discussion involving the synergism in the novel ttt-[RuCl2(PPh3)2(perhydroazepine)(isonicotinamide)] complex.

DMSO Molecule as Ancillary Ligand in Ru-Based Catalysts for Ring Opening Metathesis Polymerization

The ring-opening metathesis polymerization (ROMP) of norbornene (NBE) occurs in the presence of the fac-[RuCl 2 (S-DMSO) 3 (O-DMSO)] complex and ethyldiazoacetate (5 µL), where DMSO is S- or O-bonded dimethylsulfoxide. The yield is 62% (PDI = 1.64) at room temperature for 5 min and 88% (PDI = 1.93) at 50 oC for 30 min, with [NBE]/[Ru] = 516 in CHCl 3 . The yield is 90% (PDI = 1.64) in the presence of NBu 4 ClO 4 at room temperature for 5 min. The complex is practically inactive when one or two molecules of DMSO are replaced by pyridine, imidazole, 2-methyl-imidazole or benzimidazole. The in situ formation of the catalytic species and the behavior of the DMSO molecules as ancillary ligands in the reactivity of the Ru II complexes are discussed.

Metátese de olefinas no Brasil: "Brazil is romping it!"

Some aspects of the olefin metathesis reactions are summarized here (types of reactions, mechanism and catalysts). In particular, the research groups that have been working on this chemistry in Brazil are presented. The main goal of this paper is to make this type of reaction more widely known in the Brazilian chemical community.

Compostos nitrogenados em bebidas destiladas: cachaça e tiquira

Ammonium ion, urea and amino acids were quantified by using colorimetric methods in 51 samples of sugar cane spirit (cachaca) and 9 samples of cassava spirit (tiquira). The average contents of ammonium ion for sugar cane (0.013mmoles/L) and cassava (0.010mmoles/L) spirits are similar. Tiquiras present average contents of amino acids (0.290mmoles/L) and urea (1.45mmoles/L) higher than in sugar cane, which are 0.093mmoles/L and 0.316mmoles/L, respectively.

Trans effect and trans influence in ruthenium(II) tetraammines: Imidazole as a probe ligand

The following substitution reactions: trans−[Ru(NH3)4L1(H2O)]2++L2⇌k−1k1trans−[Ru(NH3)4L1L2]2−+H2O, where L1 = phosphite, phosphine, AsPh3 or SbPh3, and L2 = imidazole, have been studied under pseudo-first order conditions. The reaction proceeds through an Id dissociative mechanism. The trans effect of L1 has been estimated based on the k1 values: SbPh3 < AsPh3 < PBu3 < P(Ph)3 ∼ dppe < P(OMe)3 < P(OEt)3 < P(OBu)3 < P(OPri)3. The trans effect series obtained with electrophilic L2 ligands (pyrazine and isonicotinamide) for the same phosphorus(III) ligands (L1) were similar. The position of L1 in these series can be related to the α or π character of L1. The trans influence series has been written based on the reciprocal of Keq = k1k−1: P(OPri)3P(OEt)3P(OBu)3 < P(OMe)3 < P(Ph)3 < P(Bu)3 < AsPh3 < SbPh3 < dppe.

ROMP como um método versátil para a obtenção de materiais poliméricos diferenciados

Ring Opening Metathesis Polymerization (ROMP) of cyclic olefins is a powerful transition metal-catalyzed reaction for syntheses of polymers and copolymers. The key feature of this reaction is the [2+2]-cycloaddition mechanism, with retention of the olefinic unsaturation in the polymer chain and occurrence of living polymerization. With the development of metal-carbene type catalysts for this process, many addressed polymeric materials have been successfully prepared to be employed in several fields of the science and technology. This review summarizes recent examples of syntheses of polymers with amphiphilic features such as block, graft, brush or star copolymers; as well syntheses of biomaterials, dendronized architectures, photoactive polymers, cross-linked or self-healing materials, and polymers from renewed supplies.