OXYGEN IN THE COVID-19 CONTEXT: WHAT WE KNOW ABOUT THE MOLECULE WE BREATHE AND THE CENTRAL ROLE OF CHEMISTRY. In this work, the role of chemistry in the coronavirus disease 2019 (COVID-19) pandemic is highlighted through the medical oxygen supply crises in Brazil, as an example of oxygen utility in health. Starting from oxygen chemical characterization, the oxygen cycle in nature is discussed to show how oxygen is formed through photosynthesis, followed by the description of the industrial oxygen production from atmospheric air, including physical-chemical aspects. The use of medical oxygen concentrator is presented and how this device works from the chemical point of view. Besides, the noninvasive and painless oximetry is described in terms of how oxygen saturation level in blood is measured using LED - light emitting diode.

Green hydrogen is a fuel capable of promoting sustainable energy development and is gaining attention in the current global energy transition framework. The global shift toward decarbonization has triggered a substantial boost in the hydrogen industry. This study presents an overview of the current status of hydrogen production, regulation of the green hydrogen segment, hydrogen storage, distribution, and transportation, and final use and application. We also critically discuss the viability of adopting green hydrogen in terms of possible economic and environmental impacts as well as the main challenges and opportunities it represents for the Chemical Sciences.

In this work, the reaction parameters for polymeric carbon nitride synthesis by thermal polycondensation were assessed, such as type of precursor, heating rate and time of thermal treatment, in order to obtain crystalline materials with high photocatalytic performance. All synthesized materials were tested as photocatalysts in hydrogen production using ethylenediaminetetraacetic acid (EDTA) as a sacrificial reactant under visible light irradiation (λ ≥ 420 nm). The synthesis condition capable to obtain the material that reached the best performance in photocatalytic hydrogen production was using thiourea as the precursor, due to the band gap narrowing and charge recombination suppression; an intermediate heating rate (5 ºC min-1) and a longer thermal treatment time (6 h) that yielded a better crystalline solid. The combination of these effects led the S-doped polymeric carbon nitride (SPCN4 sample) to a higher photocatalytic activity, reaching the maximum hydrogen production rate of 214.75 µmol g-1 h-1.

This article is dedicated to element copper in honor to International Year of the Periodic Table celebrated in 2019. Copper is one of the oldest discovered chemical elements and manipulated by human being. In this sense, aspects about the element copper and its importance in different areas are described, from its mineral exploration through its processing and applications. Inorganic aspects such as structure of copper compounds and their main properties are presented as well the importance of this element in biological systems and organic reactions is explored, showing how essential copper is for life and society.

Nesse trabalho, um método sonoquímico de síntese de nanoestruturas de sulfeto de bismuto em 1D e 3D foi desenvolvido e comparado com uma rota sintética empregando aquecimento sob refluxo. O método sonoquímico monstrou ser mais rápido e eficiente na obtenção de nanoestruturas com alta homogeneidade morfológica. A forma e qualidade dos nanocristais foram dependentes do tipo de solvente empregado na síntese. Superestruturas em 3D semelhantes a flores foram obtidas quando etileno glicol puro foi utilizado como solvente, enquanto estruturas em 1D na forma de nanobastões foram obtidas quando utilizada uma mistura de dimetilsulfóxido e etileno como solvente.

In this work, a sonochemical method to synthesize nanostructures of bismuth sulfide in 1D and 3D framework was developed and compared with a synthetic route with heating under reflux. The sonochemical method showed to be faster and more efficient than refluxing method to obtain nanostructures with high morphological homogeneity. Form and quality of the nanocrystals were dependent on the type of solvent employed in the synthesis procedure. 3D flower-like superstructures were obtained when ethylene glycol was used as solvent, while 1D nanorods were obtained when a mixture of dimethyl sulfoxide and ethylene glycol was used as solvent.

O latex de Euphorbia conspicua foi fracionado nas frações triterpênica e irritantes I e II. Da fração triterpênica foram isolados 15 compostos já conhecidos e um novo triterpeno denominado 3β-(E)-cinamoileuforbol. A fração irritante II forneceu o 20-O-acetil-3-O-angeloil-ingenol. A atividade moluscicida dos compostos eufol, 3b-acetoxieufa-8,24-dieno, 3β-(E)-cinamoileuforbol e 20-O-acetil-3-O-angeloil-ingenol foi avaliada. O 20-O-acetil-3-O-angeloil-ingenol apresentou uma LC100 de 1 mg mL-1, a qual foi equivalente ao moluscicida padrão niclosamida. Os compostos eufol, 3b-acetoxieufa-8,24-dieno e 3β-(E)-cinamoileuforbol apresentaram uma fraca atividade moluscicida. O 3β-(E)-cinamoileuforbol foi submetido a testes de mutagenicidade (teste de Ames com TA 98, 100 e 102) na presença e ausência de ativação metabólica (mistura S9). Foram também realizados os ensaios de citotoxicidade (teste MTT) e genotoxicidade (teste dos micronúcleos, CBMN) com e sem mistura S9, em células V79 de Hamster chinês. O 3β-(E)-cinamoileuforbol revelou-se fracamente citotóxico e sem atividade mutagênica ou genotóxica.

Euphorbia conspicua latex was fractionated into triterpenic and irritant fractions I and II. The triterpenic fraction afforded 15 known compounds and a new triterpene, 3β-(E)-cinnamoyleuphorbol. 20-O-Acetyl-3-O-angeloylingenol was isolated from irritant fraction II. The compounds euphol, 3β-acetoxyeupha-8,24-diene, 3β-(E)-cinnamoyleuphorbol and 20-O-Acetyl-3-O-angeloylingenol were evaluated for molluscicidal activity. 20-O-Acetyl-3-O-angeloylingenol presented LC100 value of 1 mg mL-1, equivalent to that of the standard molluscicide niclosamide. Compounds euphol, 3β-acetoxyeupha-8,24-diene and 3β-(E)-cinnamoyleuphorbol showed low molluscicidal activity. Mutagenic assays (Ames test with strains TA 98, 100 and 102) were performed with 3β-(E)-cinnamoyleuphorbol in the presence and absence of metabolic activation (S9 mix). In V79 cells, the cytotoxicity of 3β-(E)-cinnamoyleuphorbol was evaluated using the MTT assay and the genotoxicity was assessed using the cytokinesis-block micronucleus assay (CBMN) with or without S9 mix. Mutagenic or genotoxic activity was not detected, and no significant cytotoxicity was observed for 3β-(E)-cinnamoyleuphorbol at lower doses.

Studies on identification of compounds that make up the aroma and flavor in wines involve research evaluating mainly the influence of terpenes, esters, lactones and alcohols upon these sensory characteristics. However, carbonylic compounds (CC) play an important role concerning the substances that impact aroma to these drinks. Their origin is reported to be linked to the grape's chemical composition, must fermentation or micro-oxidation occurring during storage in barrels. Some CCs, like E-ionone, E-damascenone, siryngaldehyde, can contribute a pleasant aroma and improve the wine quality whereas others are responsible for unpleasant characteristics (acetaldehyde, furfural, 5-hydroxy-methyl furfural, diacetil, E-non-2-enal, etc). A fraction of CCs present is associated with bisulfite ions in the form of hydroxyalkylsulfonic acids. Some of them are stable and play an important role in determining wine quality. The reaction involving the formation of this aduct commonly occurs with CCs of low molar mass, such as formaldehyde and acetaldehyde. The reaction involving CCs with more than three carbon atoms demands further studies.

A estrutura dos sítios metálicos na rede de CuI2SO3.CdII SO3.2H2O foi avaliada pela técnica de ressonância paramagnética eletrônica (EPR), empregando o íon paramagnético CuII como íon sonda. Essa metodologia foi capaz de distinguir os sítios de complexação dos íons M I e M II na estrutura de CuI2SO3.CdII SO3.2H2O. Os resultados indicam que CuI2SO3.CdII SO3.2H2O é dopado com íons CuII nas duas posições dos íons metálicos. Os valores baixos da razão g<FONT FACE=Symbol>||</FONT>/A<FONT FACE=Symbol>||</FONT> para o íon sonda no sítio octaédrico resultam da interação do cobre com átomos de oxigênio em ambiente tetragonal distorcido com alongamento da molécula na direção z. A baixa constante de acoplamento hiperfino A33 é explicada considerando a mistura dos orbitais d x² -y² e d z² e uma estrutura quase piramidal trigonal para o outro sítio.

An evaluation was made of the presence of paramagnetic ions in the host lattice of CuI2SO3.CdII SO3.2H2O by the electron paramagnetic resonance (EPR) technique, using copper(II) ions as paramagnetic probes. The existing M I and M II complexation sites in the double sufite structure were successfully differentiated. The results indicate that the CuI2SO3.CdII SO3.2H2O structure was doped with CuII ions in the two metal ion substitutional positions. The low g<FONT FACE=Symbol>||</FONT>/A<FONT FACE=Symbol>||</FONT> ratio for the CuII probe in the distorted octahedral site resulted from the interaction of copper ions with oxygen donor atoms in a distorted tetragonal environment, with elongation of the molecule in the z direction. The very low value of the A33 hyperfine coupling constant was explained considering the admixture of the d x² -y² and d z² orbitals and the almost trigonal pyramidal structure of the other site.

Embora o primeiro sulfito duplo de valência mista, Cu2SO3.CuSO3.2H2O, tenha sido preparado no início do século XIX por M. Chevreul, o interesse por compostos dessa natureza ressurgiu só depois da metade do século XX com a determinação da estrutura cristalina deste composto e a caracterização de seu espectro de absorção na região do infravermelho. Nos últimos anos, os estudos referentes a este tema têm se intensificado, especialmente após a descoberta da possibilidade de substituição isomórfica do Cu(II) no sal de Chevreul por diversos cátions com o mesmo estado de oxidação, gerando uma série de compostos cujas propriedades são fortemente dependentes da natureza do cátion M(II). Devido às suas propriedades interessantes, esses sistemas de valência mista podem ser usados como modelos para identificar intermediários em processos de corrosão atmosférica, bem como para avaliar o papel de metais de transição como catalisadores de autooxidação de S(IV) na conversão do SO2 na atmosfera.

Although the first mixed valence double sulfite, Cu2SO3.CuSO3.2H2O, was prepared in the early 19th century by M. Chevreul, interest in this type of compound was only rekindled in the mid-1960s, when the crystalline structure of Chevreul's salt was determined and its infrared spectrum characterized. Studies of this type of compound have been intensified in recent years, especially after the discovery that the isomorphic Cu(II) in Chrevreul's salt could be replaced by a divalent metal ion, forming an isomorphic series whose properties are strongly dependent on the nature of the M(II) cation. Because of their interesting properties, these mixed valence systems can be used as models to identify intermediates in atmospheric corrosion processes, and to evaluate the role of transition metals as catalysts of S(IV) autoxidation in the conversion of SO2 in the atmosphere.

A série isomórfica de sulfitos duplos com fórmula empírica Cu2SO3.MSO3.2H 2O (onde M é Cu, Fe, Mn ou Cd) é preparada pela substituição do Cu(II) no sal de Chevreul, Cu2SO3.CuSO3.2H 2O, por íons de metais de transição, tais como Fe(II), Mn(II) e Cd(II). Como conseqüência, as espécies isomórficas apresentam colorações distintas. Cálculos de modelagem molecular foram empregados neste trabalho para o centro dimérico [CuI2(SO3) 2(SO3)2]6- . O espectro eletrônico do sal de Chevreul consiste de uma banda de transferência de carga em 425 nm associada ao cromóforo [CuI2(SO3) 2(SO3)2]6- e duas transições de campo ligante a 785 e 1000 nm envolvendo distorção de Jahn-Teller dos níveis do Cu(II). Além disso, uma banda adicional de transferência de intervalência é observada em 500 nm, sendo responsável pela sua coloração vermelha característica. A substituição do íon Cu(II) pelos íons Fe(II), Mn(II) e Cd(II) não elimina a banda de absorção em 425 nm, associada à transição de transferência de carga centrada nos sítios Cu(I), porém a banda original em 500 nm desaparece, em concordância com a atribuição de transição intervalência.

The isomorphic series of double sulfites with empirical formula Cu2SO3.MSO3.2H 2O (where M is Cu, Fe, Mn, or Cd) have been prepared from the Cu(II) replacement by transition metal ions such as Mn(II), Fe(II) and Cd(II) ions in Chevreul's salt, Cu2SO3.CuSO3.2H 2O. As a consequence, the isomorphic species present distinct colors. Molecular modeling calculations were carried out for the dimeric [CuI2(SO3) 2(SO3)2]6- center. The electronic spectra of the Chevreul's salt consist of a charge-transfer band around 425 nm associated with the [CuI2(SO3) 2(SO3)2]6- chromophore and two ligand field transitions at 785 and 1000 nm involving the Jahn-Teller splitting of the Cu(II) levels. An additional intervalence-transfer band, responsible for its characteristic red color, can be found at 500 nm. The replacement of the Cu(II) ions for Fe(II), Mn(II) and Cd(II) does not eliminate the absorption band at 425 nm, supporting its assignment as a charge-transfer transition centered on the Cu(I) sites; while the original band at 500 nm disappears, in agreement with its intervalence transfer nature.

Estudo longitudinal vem acompanhando todas as crianças nascidas em Pelotas, Rio Grande do Sul, no ano de 1982. Suas trajetórias escolares mostraram-se fortemente determinadas pela variável gênero, mesmo quando eliminados por estatística outros fatores intervenientes. Um estudo com 84 professoras/es buscou identificar que processos estão presentes na escola e nas representações que ajudem a compreender essas diferenças no desempenho escolar das meninas e dos meninos. A análise do material aponta para a maneira feminina de exercer o magistério que atravessa a prática docente, para a profecia auto-realizadora referendada no critério de bom comportamento e para a estreita relação entre gênero e saber regulados pelos regimes de verdade.

A longitudinal study has been following all the children born in Pelotas, Rio Grande do Sul, during 1982. Their academic background showed strong correlation with gender, even when eliminating other variables through statistical procedures. A study with 84 teachers tried to identify the process present at schools that could help to understand the differences between the girls' and boys' academic performances. The analysis points out to the female bias in teaching practice, to the self-fulfilling profecy reflected in the good-behavior criterion and to the close relationship between gender and knowledge determinated by the truth-regulations.