Circular chemistry (CC) is an approach for establishing chemical processes to become truly circular and sustainable. It adopts the principles of circular economy (CE), employing life cycle approaches and systems thinking, which help to understand and address the sustainability issues of chemical processes and products. Within this whole context, it is possible to identify some problems of the current lifestyle, such as plastic waste disposal, CO2 emission, e-waste, among others, which need to be addressed accordingly. The reuse provided, well-structured within the context of circular chemistry, can bring benefits in all spheres: social, environmental and economic. Thus, the purpose of this revision is to present CE and CC as the pillars for a sustainable development, bringing discussions about: CE and CC systems; sustainable chemistry; and chemistry 4.0, which embeds digitization, sustainability, and circular economy in industrial chemical processes. Through the knowledge of chemistry, both CC and CE can contribute with innovative methods and processes which maximize benefits, eliminating, or, at least, reducing adverse impacts, thus contributing to construct a mutually beneficial relationship between science and society, its surroundings, and the environment. Therefore, implementing this new model is an opportunity that challenges the human imagination in building a better world.

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.

Medicines are employed in undergraduate courses as motivational strategy. The experiment herein developed compares the extraction of paracetamol from generic and brand name drugs. Tablets were used from two commercial sources purchased from local drugstores. Twenty tablets of each drug type were individually weighed to average weight analysis and mass dispersion was statistically analyzed in simulating of quality control. Average weight had variation in accordance with the limit of ±5% specified by Brazilian Pharmacopeia. Tablets of each drug were pulverized and extracted in triplicate with ethyl acetate, and the active ingredient was obtained and identified by melting point and FTIR analyzes. Comparing different student groups at different times, there was change in the mass of paracetamol extracted by a simple extraction, affording mass recovery in the range of 59±17% to 28±1%. However, mass recovery of paracetamol extraction of generic and brand name drugs was similar in each student group. Under Soxhlet extraction condition mass recovery was 80-85%. The procedure developed was adequate to undergraduate laboratory, involves simple infrastructure and execution, tablets are easily obtained, and allows discussion on pharmaceutical equivalence and interchangeability.

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.

This paper deals with the solubility and reactivity of gases, especially in water, covering the main aspects that influence the dissolution process, namely polarizability of atoms or molecules in gas phase and their ability to react with the solvent. The discussion highlights the importance of solubility of gases in several biological processes, such as respiration and photosynthesis, hydrogen storage and industrial processes, as the production of carbonated beverages. The discussion also addresses the importance of gas solubility in atmospheric chemistry and aquatic environments.

Quinones are a group of semi-volatile organic substances, ubiquitous in nature, belonging to the class of oxygenated polycyclic aromatic hydrocarbons (Oxygenated PAH). These compounds are formed in biogenic processes, through the oxidative metabolism of endogenous compounds, such as catecholamines, estrogen hormones and xenobiotics, as well as directly emitted to the atmosphere, through the incomplete combustion of organic matter, especially the fossil fuels. Additionally, the quinones are formed in the atmosphere by photooxidation of Polycyclic Aromatic Hydrocarbons (PAH). Their reduction products (semiquinones and hydroquinones) are of toxicological interest, due to their ability in generate reactive oxygen species, which may cause damage to membranes, proteins and DNA and, among others damages, may lead to carcinogenesis and induce apoptosis. The most frequently used analytical methods for quantification of quinones in the atmosphere, either in its original form or as derivatized compounds, are high-performance liquid chromatography coupled to mass spectrometry (HPLC-MS) and gas chromatography coupled to mass spectrometry (GC-MS). This review aims to highlight the chemical properties of 1,2-naphthoquinone, 1,4-naphthoquinone, 1,4-benzoquinone, 9,10-phenanthraquinone and 9,10-anthraquinone, the more volatile, reactive and abundant quinones in the atmosphere, as well as the methods usually employed for their determination.

<p>We described herein a solvent-free synthesis of acetanilide developed in the context of green chemistry. The synthetic approach consisted of the reaction of aniline with acetic anhydride without additives, while using smaller amounts of reagents and water than previously described for this undergraduate experiment. The E Factor was 0.6 by experienced chemists and 0.9 by students.</p>

Análise de Novena, canção de 1964 que inaugurou a carreira de compositores da dupla do então cantor-instrumentista Milton Nascimento e do letrista Márcio Borges. O contexto histórico, especialmente a partir de depoimentos dos dois artistas (BORGES, 1996, 2010, 2012; NASCIMENTO, 1993, 1996, 2009, 2012; BORGES e NASCIMENTO, 2012a, 2012b, 2012c, 2012d, 2012e, 2012f, 2012g, 2012h, 2012i, 2012j) e elementos melódicos, harmônicos e da relação texto-música da canção, percebidos na transcrição da única gravação de Milton Nascimento (NASCIMENTO e BORGES, 1993), apontam para a síntese de uma estética que se consolidou no Clube da Esquina, cujos membros desenvolveram carreiras com perfis ecléticos e uma linguagem musical estilisticamente híbrida.

Analysis of Novena, a song from 1964 that launched the career, as composers, of the singer-instrumentalist Milton Nascimento and lyricist Márcio Borges. The historical context, especially that told by the artists (BORGES, 1996, 2010, 2012; NASCIMENTO, 1993, 1996, 2009, 2012; BORGES e NASCIMENTO, 2012a, 2012b, 2012c, 2012d, 2012e, 2012f, 2012g, 2012h, 2012i, 2012j) and melodic, harmonic and text-painting elements, observed in the transcription of the only and late recording by Milton Nascimento (NASCIMENTO and BORGES, 1993) point out to a synthesis of an aesthetics that consolidated into the Brazilian Clube da Esquina (Corner's Club), whose members developed careers of eclectic profiles and a stylistically hybrid musical language.

The solubility of organic compounds is a topic of great importance in chemistry and of interest in several areas, such as materials, drugs and the environment. In this paper, the solubility of these species is discussed in terms of their properties, such as the predominant type of chemical bond, molecular structure, polarity and types of intermolecular interactions. Examples of biological processes fundamental for sustainability of life and related with the solubility of chemical species are presented and discussed.

Estabeleceu-se, neste trabalho, uma equação barométrica para relacionar as grandezas físicas da baixa atmosfera terrestre: pressão, altitude e temperatura, com a razão entre a constante de Boltzmann e a massa média das moléculas dos gases constituintes. Para uma altitude geopotencial não superior a 33 km e considerando-se a massa média da molécula 4,809 x 10-26 kg, obteve-se um valor médio para a constante de Boltzmann de 1,373 x 10-23 J/K

In this work, a barometric equation was established to relate the physical quantities of the low atmosphere: pressure, altitude, and temperature with the ratio between the Boltzmann's constant and the medium mass of molecules of the constituent gases. For geopotential altitude not superior to 33 km and assuming the medium mass of the molecule 4,809 x 10-26 kg, a medium value was obtained for Boltzmann's constant of 1,373 x 10-23 J/K

O presente trabalho apresenta o estudo sobre 16 HPAs prioritários em material particulado atmosférico de três sítios próximos a Salvador-BA: (i) Estação da Lapa, estação de ônibus da Região Metropolitana de Salvador; (ii) Porto de Aratu, impactado por intenso movimento de matérias-primas e (iii) Bananeira, localizado na Ilha de Maré, vilarejo que tem como principais atividades a pesca e artesanato. Resultados mostraram que o BbF (0,130-6,85 ng m-3) foi o HPA com as concentrações mais elevadas em Aratu e Bananeira e CRY (0,075-6,85 ng m-3) apresentou nível mais elevado na Lapa. As fontes de HPAs nos sítios estudados foram principalmente de origem antrópica, tais como veículos de pequeno e grande portes, carregamentos do porto, ressuspensão de partículas do solo, queima de diesel das embarcações e a queima de carvão e madeira para produção de energia.

The present work has aimed to determine the 16 US EPA priority PAH atmospheric particulate matter levels present in three sites around Salvador, Bahia: (i) Lapa bus station, strongly impacted by heavy-duty diesel vehicles; (ii) Aratu harbor, impacted by an intense movement of goods, and (iii) Bananeira village on Maré Island, a non vehicle-influenced site with activities such as handcraft work and fisheries. Results indicated that BbF (0.130-6.85 ng m-3) is the PAH with highest concentration in samples from Aratu harbor and Bananeira and CRY (0.075-6.85 ng m-3) presented higher concentrations at Lapa station. PAH sources from studied sites were mainly of anthropogenic origin such as gasoline-fueled light-duty vehicles and diesel-fueled heavy-duty vehicles, discharges in the port, diesel burning from ships, dust ressuspension, indoor soot from cooking, and coal and wood combustion for energy production.

The perception of the flavor is an important attribute of quality in marine fish and other seafoods, being the first and main factor of discrimination for the evaluation, later acceptance and preference of the product by the consumer. Recently, the simple bromophenols have been considered an important group of key flavor compounds occurring in a wide variety of seafood species like fishes, mollusks, crustaceans and algae. When present in high concentration, in seafood, the bromophenols produce an undesirable flavor and are associated with inferior quality. Meanwhile, when present in low concentration levels (for example ng g-1) these compounds produce a desirable marine - or ocean-like - flavor and enhance the existing flavor in seafood. Indeed, simple bromophenols are widespread in seafood but virtually absent in freshwater fish. Herein we present a review on these flavor components found in the marine environment.

Neste trabalho, são apresentados os potenciais de meia-onda de redução, determinados para 3-nitrofluoranteno (3-NF) = -0,51V, 1-nitropireno (1-NP) = -0,61V, 6-nitrocriseno (6-NC) = -0,64V, e 9-nitroantraceno (9-NA) = -0,84V. Os experimentos de voltametria cíclica com os nitro-PAH foram conduzidos em N,N-dimetilformamida anidra (DMF) contendo perclorato de tetraetilamônio 0,1 mol L-1 (TEAP), usando-se uma célula de três compartimentos, equipada com eletrodos de trabalho e auxiliar de platina e eletrodo de referência de Ag/AgI (fio de prata imerso em DMF / TEAP 0,1 mol L-1, contendo iodeto de tetrabutilamônio 0,05 mol L-1). Esses potenciais podem ser ordenados do menos negativo para o mais negativo, o que corresponde à mesma ordem com que decresce a ação mutagênica direta (3-NF >> 1-NP > 6-NC >> 9-NA). Assim, o 3-NF, que apresentou o potencial de meia-onda menos negativo é, entre os nitro-PAH estudados, o de maior atividade mutagênica. Deste modo, estas propriedades podem ser utilizadas como indicativas do risco à saúde humana da exposição a nitro-PAH, sendo, portanto, de grande importância em estudos toxicológicos.

In this work, we report measured electrochemical half-wave reduction potentials of 3-nitrofluoranthene (3-NF), 1-nitropyrene (1-NP), 6-nitrochrysene (6-NC) and 9-nitroanthracene (9-NA): = -0.51V; -0.61V; -0.64V; and -0.84V respectively. The cyclic voltammetry experiments with the nitro-PAH were carried out in anhydrous N,N-dimethylformamide (DMF), containing 0.1 mol L-1 tetraethylammonium perchlorate (TEAP) using a three-compartment cell fitted with Pt working and auxiliary electrodes, and a Ag/AgI reference electrode (a silver wire in 0.1 mol L-1 DMF/TEAP containing 0.05 mol L-1 tetrabutylammonium iodide). These potentials can be ordered from the less to the more negative value, which corresponds to the same order by which the direct-acting mutagenicity decreases (3-NF >> 1-NP > 6-NC >> 9-NA). Thus, 3-NF, which shows the less negative first half-wave potential value is the more active mutagenic amongst the nitro-PAH studied. In this way, these properties may be used as an indicative of the health risks, asociated to nitro-PAH exposure, and thus being of great importance in toxicological studies.

A importância da produção de biodiesel, nos últimos cinco anos, é apresentada a partir de artigos científicos publicados e patentes depositadas. Foi realizada uma análise crítica sobre as fontes oleaginosas mais utilizadas como matéria-prima para produção de biodiesel, os catalisadores e os métodos de acompanhamento da reação de transesterificação. Também foram avaliados estudos comparativos entre emissões de diesel fossil e misturas, em várias proporções, com biodiesel. Finalmente, foram indicados desafios enfocando aspectos tecnológicos, agronômicos e de infra-estrutura para produção de biodiesel.

The importance of biodiesel production was analyzed based on scientific articles and patents. A critical analysis was presented on the most used oil sources, the catalysts and the methods to verify the transesterification yields. Also analyzed were the comparative studies on emissions from pure fossil diesel and mixtures with biodiesel in variable proportions. Finally some challenges and considerations focused on technological, agronomic and infrastructure aspects of biodiesel production were indicated.

This article decribes a simple and systematic method to interpret an infrared spectrum using a flow chart to elucidate the structure of a simple organic compound. It is aimed at undergraduate courses of organic chemistry to make beginners proficient. The proposed flow chart for infrared spectrum interpretation and characterization of organic compounds is suitable for theoretical and experimental courses.