Journal of the Brazilian Chemical Society This is an RSS file. You can use it to subscribe to this data in your favourite RSS reader or to display this data on your own website or blog.

Synthesis and Evaluation of the Fungal Activity of New Pyrazole-Carboxamides against Colletotrichum gloeosporioides
The pyrazole core has been recognized by their biological properties and included in the synthesis of modern agrochemicals. Part of these studies consists of making structural modifications to pesticides for commercial purposes to increase efficacy. In this article, we present the synthesis of four new pyrazol-4-carboxamide 8a-8d derivatives (PCD), through a four-step synthetic protocol, starting with edaravone 1 and primary amines like benzo-fused, aliphatic, and hydrazines, through a process of low environmental impact. Synthesized derivatives were evaluated against one fungal strain of Colletotrichum gloeosporioides BA3...
Source: Journal of the Brazilian Chemical Society - August 19, 2020 Category: Chemistry Source Type: research

Dereplication of Aporphine Alkaloids by UHPLC-HR-ESI-MS/MS and NMR from Duguetia lanceolata St. -Hil (Annonaceae) and Antiparasitic Activity Evaluation
Although the genus Duguetia is well known for producing alkaloids as chemical constituents, there are no reports of alkaloids identified in the species D. lanceolata. Thus, aiming to identify the chemical composition of this species, the dereplication of alkaloidic phase was performed by use of ultra-high performance liquid chromatography high resolution electrospray ionization tandem mass spectrometry (UHPLC-HR-ESI-MS/MS) and 1H nuclear magnetic resonance (NMR). The chromatographic fractionation of the alkaloid extract from Duguetia lanceolata (Annonaceae) leaves afforded four fractions (I-IV) that were shown to be compos...
Source: Journal of the Brazilian Chemical Society - August 19, 2020 Category: Chemistry Source Type: research

Optimization and Validation of LLE-LTP and QuEChERS Methodologies for Determining 2,4-D in Water Samples
2,4-Dichlorophenoxyacetic acid (2,4-D) has been one of the main herbicides used to control weeds, however, due to its high use it can promote episodes of environmental contamination. Therefore, this study aimed to optimize and validate the liquid-liquid extraction with low-temperature partition (LLE-LTP) and the quick, easy, cheap, effective, rugged, and safe (QuEChERS) methods for determining 2,4-D in water samples by high performance liquid chromatography with diode array detector. The recovery percentages of the two methodologies were close to 100 ± 3%, and the limits of quantification were 2.0 and 3.1 µg L-1 for LLE-...
Source: Journal of the Brazilian Chemical Society - August 19, 2020 Category: Chemistry Source Type: research

Effects of Temperature and Concentration on the Determination of PET Viscosity
This work describes the use of experiment planning to investigate the effects of the variables temperature and concentration of the polymer solution on the viscosity test of polyethylene terephthalate (PET). For this, the response surface methodology was based on a central composite rotatable design (CCRD) to optimize the combinations of the analytical conditions. With the analysis of the standard sample of PET with intrinsic viscosity of 0.630 ± 0.008 dL g-1 and 2-chlorophenol solvent, it was observed that the solution flow temperature and PET concentration caused significant effects on the results, while the storage tem...
Source: Journal of the Brazilian Chemical Society - August 19, 2020 Category: Chemistry Source Type: research

Omega-3 and Omega-6 Determination in Nile Tilapia’s Fillet Based on MicroNIR Spectroscopy and Multivariate Calibration
Tilapia (Oreochromis niloticus) is the most cultivated fish species in Brazil. Studies have shown that fish consumption is related to the prevention of cardiovascular diseases due to its high contents of polyunsaturated fatty acids, as omega-3 (n-3) and omega-6 (n-6). In this sense, a new method to determine omega-3 and omega-6 by near-infrared (NIR) spectroscopy and multivariate calibration based on partial least squares (PLS) was proposed. Spectra of fillets of Nile tilapias packed under vacuum were obtained and compared to the reference method (gas chromatography) used for quantification of fatty acids. The outliers wer...
Source: Journal of the Brazilian Chemical Society - August 19, 2020 Category: Chemistry Source Type: research

Electroanalytical Method for Determination of Trace Metals in Struvite Using Electrochemically Treated Screen-Printed Gold Electrodes
We present an electroanalytical method using square-wave anodic stripping voltammetry on electrochemically-treated screen-printed gold electrodes to the simultaneous determination of lead(II), copper(II) and mercury(II) in struvite (natural fertilizer produced from urine). Electrochemical treatment via cyclic voltammetry of the working electrodes increased surface rugosity that improved the electroanalytical responses for the three metals. Under optimized conditions and using a deposition time of 90 s, the proposed method presented the following limit of detection values: 1.3 µg L-1 for lead(II), 2.0 µg L-1 for copper(II...
Source: Journal of the Brazilian Chemical Society - August 19, 2020 Category: Chemistry Source Type: research

Accessing Basic Sites on Modified CoFe2O4 Nanoparticles: Addressing the Selective Oxidation of Benzyl Alcohol and Unraveling the Au:Pd Ratio Effects by XPS
AuPd nanoparticles have gained substantial attention due to their application in selective oxidation of alcohols. However, due to the radical nature of the oxidation of benzyl alcohol, under specific conditions, even without a catalyst, the reaction occurs and affects the selectivity of the system. Therefore, we aimed to develop a catalyst that enables the control of the oxidation leading to higher reaction selectivity. To accomplish this, we have prepared a catalytic support comprised of CoFe2O4 nanoparticles impregnated with Sr(OH)2 that presented a significant control of the reaction selectivity without any metal or ext...
Source: Journal of the Brazilian Chemical Society - August 19, 2020 Category: Chemistry Source Type: research

Crystallographic Changes Accompanying the Verwey Transition in a Magnetite from Steatite
The crystallographic structural analysis of the magnetite of a steatite rock at 298 K, (saturation magnetization, σ = 95.0 J T-1 kg-1) showed two cubic networks and, below Verwey temperature (TV ca.120 K) a monoclinic structure, basing on their cell dimensions and different transitional behaviors when reducing the temperature. A monoclinic structure was identified from their cell dimensions and different transition behaviors when reducing the temperature. The average chemical formula of this almost stoichiometric magnetite was deduced from the chemical analysis, 298 K-M össbauer and the structural refinement. The Rietve...
Source: Journal of the Brazilian Chemical Society - August 19, 2020 Category: Chemistry Source Type: research

Antibacterial Activity of 2-Amino-1,4-naphthoquinone Derivatives against Gram-Positive and Gram-Negative Bacterial Strains and Their Interaction with Human Serum Albumin
A series of 2-amino-1,4-naphthoquinone derivatives (NQA-NQF) was synthesized by alternative methods (ultrasonication and microwave irradiation), with yields ranging from 40 to 71%, and without the need of further recrystallization. Each compound was evaluated against four Gram-positive (Bacillus subtilis, Enterococcus faecalis, Staphylococcus aureus and Bacillus cereus) and five Gram-negative (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Acinetobacter baumannii and Klebsiella pneumoniae positive β -lactamase) bacteria strains. The NQF was the most active amino-naphthoquinone derivative with minimum inh...
Source: Journal of the Brazilian Chemical Society - August 19, 2020 Category: Chemistry Source Type: research

Phytochemical Analysis, Multi-Element Composition and Biological Activities of Extracts and Lupenone from Albizia inundata (Mart.) Barneby & J.W.Grimes
In this study, antimicrobial activity of extracts and lupenone from A. inundata (Fabaceae, Mimosoideae), were tested. In addition, the multi-element composition of the leaves, bark and stems (heartwood) of A. inundata was evaluated using inductively coupled plasma optical emission spectrometry (ICP OES). Lupenone was isolated in the petroleum ether extract of leaves, for the first time. Biological assays were conducted to evaluate the antimicrobial (antibacterial, antifungal and antiparasitic) of extracts, their fractions and lupenone. The results showed antimicrobial and antileishmanial activity of these compounds, which ...
Source: Journal of the Brazilian Chemical Society - August 19, 2020 Category: Chemistry Source Type: research

Synthesis, Characterization, Absorption and Fastness Properties of Novel Monoazo Dyes Derived from 1-Phenyl-3-amino-4-(2-thiazolilazo)pyrazol-5-one
Monosubstitute thiazolyl amines were diazotized in acetic acid, coupled to 1-phenyl-3-aminopyrazol-5-one (1a-1c) and acetylated to obtain the 2a-2c dyes. The dyes were characterized by elemental analysis and spectroscopic (Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR), ultraviolet (UV)) methods. The effects on the visible absorption spectra of the substituents present, solvents, pH, concentration and temperature were investigated in detail. Tautomerism of the dyes were investigated by spectroscopic methods. Fastness properties of dyes were studied using the standard method for the assessment of color ...
Source: Journal of the Brazilian Chemical Society - August 19, 2020 Category: Chemistry Source Type: research

Synthesis and Evaluation of Nematicidal Activity of Compounds Derived from Norbornadiene
This study describes the synthesis of 21 novel esters derived from norbornadiene and evaluation of their potential activity against Meloidogyne javanica. The esters 5-25 presented 50% mortality of the nematodes. The acid 3 and the ester 4 caused 96 and 93% mortality of the nematodes, respectively. The lethal concentration to kill 50% of the nematodes (LD50) were determined as being 11.8 µg mL-1 for the acid 3 and 99.4 µg mL-1 for the ester 4. According to the results obtained it is believed that polarity seems to be a key factor for the higher activity of compound 3 compared to structurally similar ester derivatives. (So...
Source: Journal of the Brazilian Chemical Society - August 19, 2020 Category: Chemistry Source Type: research

Mechanistic Investigation of DBU-Based Ionic Liquids for Aza-Michael Reaction: Mass Spectrometry and DFT Studies of Catalyst Role
1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU)-based ionic liquids (ILs) has exhibited a high catalytic activity in the aza-Michael reactions compared to conventional catalysts and with imidazole-based ILs. In the present work DBU-based ILs showed high catalytic potential for aza-Michael addition of aromatic amines to 2-cyclohexen-1-one under solvent-free condition. Electrospray ionization-mass spectrometry (ESI-MS) and density functional theory studies have been carried out to provide an effective activation mode of DBU-based ILs in aza-Michael addition. Our results show that both the presence of the acid hydrogen in the IL and...
Source: Journal of the Brazilian Chemical Society - August 19, 2020 Category: Chemistry Source Type: research

Zinc Hexacyanoferrate/Multi-Walled Carbon Nanotubes Films for Rechargeable Aqueous Batteries
Zinc hexacyanoferrate (ZnHCF) is a Prussian Blue analog and can be intercalated by both monovalent and divalent ions. ZnHCF/multi-walled carbon nanotube (MWCNT) film could be used as a cathode for zinc ions battery. Carbon nanotubes improved significantly the electrochemical performance of the electrode. It is described the preparation of ZnHCF/MWCNT films by the interfacial method with cyclohexane/water mixture as solvent. The crystal structure, morphology, and microstructure of the as-prepared products were characterized by X-ray diffraction, scanning electron microscopy, Mossba üer, Raman spectroscopy, and infrared spe...
Source: Journal of the Brazilian Chemical Society - August 19, 2020 Category: Chemistry Source Type: research

A Highly Selective Fluorescent Chemosensor for Al3+ Based on 2,2’:6’,2”-Terpyridine with a Salicylal Schiff Base
Two 2,2 ’ :6 ’ ,2 ” -terpyridine-based Schiff bases (TPySSB and TPySB) have been synthesized. The TPySSB shows remarkable selective ‘ off-on ’ fluorescence for Al3+ in combination with photoinduced electron transfer (PET) mechanism and C=N isomerization mechanism. Chemosensor TPySSB binds Al3+ in a 1:2 ratio with an association constant 6.8 × 105 (correlation coefficient (R2) = 0.98) and this 1:2 stoichiometric model is established on Job ’ s plot and 1H nuclear magnetic resonance (NMR). Comparing TPySSB and TPySB, it is of great importance the existence of oxygen atom of hydroxyl group in salicylidene due to...
Source: Journal of the Brazilian Chemical Society - August 19, 2020 Category: Chemistry Source Type: research