BOOKS by Adelio A S C Machado
Introduction to Green Chemistry Metrics - A Systemic Vision (Book), Jun 4, 2014
ABSTRACT: Prefácio. Preâmbulo. 1 - Introdução ao Conceito de Métricas. 2 -Métricas de Massa. 3 - ... more ABSTRACT: Prefácio. Preâmbulo. 1 - Introdução ao Conceito de Métricas. 2 -Métricas de Massa. 3 - Métricas Holísticas. Conclusão. Referências. (254 pag.)
Preface, Prologue. 1 - Introduction to Metrics. 2 - Mass Metrics. 3 - Holistic Metrics. Conclusion. References. (254 p.)
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GREEN CHEMISTRY by Adelio A S C Machado
Quim. Nova, 43 (10) 1510-1521 (2020), 2020
This paper discusses 286 proposals and reports of Green Chemistry (GC) teaching experiences, in p... more This paper discusses 286 proposals and reports of Green Chemistry (GC) teaching experiences, in papers of the Journal of Chemical Education (JCEd) until 2019. The analysis was based on previous categories: source-problem, paper focus, subjects/area of knowledge, target groups, GC contents, type of approach and purpose(s) of the proposal. A list of possible characteristics of each category served as an example to compare with the information resulting from the analyses, and thus improve the discussions. In 127 papers, GC and its teaching were associated, albeit generally, with the theme of sustainability/ sustainable development, which points to its potential to face environment-related aspects of chemistry in teaching. A systemic vision in the interconnection between GC and sustainability/sustainable development appeared more explicitly in 39 papers up to 2019. So far, the analysis highlights a certain reproduction of traditional chemistry teaching, and little evidence of the particularities of GC teaching. Despite the intention of inserting GC into chemistry teaching, proposals for its incorporation are often made superficially, more as an addendum or an extra quality than a specific goal. More methodological detail of the experiments carried out is needed to help in the dissemination of GC in the training curriculum of chemists. The discussions and reports on teaching approaches based on Systems Thinking showed the opening of a promising new methodological challenge within this theoretical paradigm.
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Quim. Nova, 43(10) 1510-1521(2020), 2020
GRAPHICAL ABSTRACT
This paper analyses 286 papers on Green Chemistry published in the Journal of ... more GRAPHICAL ABSTRACT
This paper analyses 286 papers on Green Chemistry published in the Journal of Chemical Education regarding the relationships between Green Chemistry, Sustainability and Systems Thinking present in teaching approaches.
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Quim. Nova, 43(10) 1510-1521 (2020), 2020
SUPPLEMENTARY MATERIAL
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QUÍMICA - Boletim da Sociedade Portuguesa de Química, 43(152) 67-78 (2019), 2019
THE TREATMENT OF THE ATOM ECONOMY IN THE SYLLABUS AND TEXTBOOKS FOR SECONDARY EDUCATION
An analy... more THE TREATMENT OF THE ATOM ECONOMY IN THE SYLLABUS AND TEXTBOOKS FOR SECONDARY EDUCATION
An analysis of the recent inclusion of Green Chemistry in the syllabus of Physics and Chemistry A of secondary education (grade 11), focused on the treatment of the atom economy, in the programmatic text of the Ministry of Education and the six certified textbooks for the discipline is described. It was found that the subject was introduced with insufficient detail in the syllabus proposal, which is diffuse and erroneous. For instance, it ignores that the term atom economy is used for both a concept and a greenness metric and that the mass metrification of synthetic reactions requires other metrics. The treatment given to the subject in the proposal probably contributed for the differences found in its development in the textbooks and for the problematic/erroneous statements they include. This situation requires clarification and therefore a global treatment of the metrification of the mass greenness of the use of matter in chemical reactions is included, as well as a very simple example, the synthesis of tin(IV) iodide, to help understanding the different features of greenness captured by each metric.
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QUÍMICA - Boletim da Sociedade Portuguesa de Química, 42 (150) 165-169 (2018), 2018
GREEN CHEMISTRY: THE ATOMIC ECONOMY OR THE ATOMIC UTILIZATION METRIC - WHO IS THE AUTHOR, TROST O... more GREEN CHEMISTRY: THE ATOMIC ECONOMY OR THE ATOMIC UTILIZATION METRIC - WHO IS THE AUTHOR, TROST OR SHELDON?
The bibliography on the conception of the Green Chemistry mass metric called Atom Economy (AE) was thoroughly reviewed. The authorship of this metric has been commonly attributed to the academic chemist Barry Trost in sequence of its presentation of the Atom Economy qualitative concept, but the analysis of the literature shows that its author was Roger Sheldon, who calculated the metric before, in an industrial synthesis context, calling it Atom Utilization (AU). The origin of this imprecision is discussed, as well as the influence of the different professional contexts of the two chemists (academic vs. industrial) on their mindset for visualization of the Atom Economy idea and calculation of the corresponding metric.
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QUÍMICA - Boletim da Sociedade Portuguesa de Química, 42(148) 47-58 (2018), 2018
GREEN CHEMISTRY PRINCIPLES AND LABORATORY SAFETY
An analysis of the usefulness of the Twelve Prin... more GREEN CHEMISTRY PRINCIPLES AND LABORATORY SAFETY
An analysis of the usefulness of the Twelve Principles (Anastas and Warner) and the Second Twelve Principles (Winterton) of Green Chemistry (GC) for supporting the teaching of Laboratory Safety (LS) has been developed. An assessment of the contents of both groups of principles that are relevant for LS, their scope, ways of application, etc., is presented, followed by a brief discussion on approaches suitable for their use in teaching. The discussion suggests that the Twelve Principles, being generic and intuitive prescriptions, may support procedures for the introduction of the teaching of LS in the first years of university degrees and in secondary schools, while the use of the Second Twelve Principles is more problematic, seeming more suitable for advanced years of university courses, as they refer to more specific aspects of the implementation of chemistry. In both cases, the aim will be acquiring synergies with a LS and GC integrated teaching. Laterally the analysis showed that these teaching procedures were suitable for including a discussion of the Twelve Principles limitations, some of which emerged from a global view of the results. The huge complexities of chemistry, GC, chemical hazards, etc., and their implications on the LS teaching are also briefly considered, pointing to the urgency of adopting a systemic, instead of the current reductionist mindset used in chemistry education, to deal with the required reshaping of chemical safety teaching and practice.
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ASSESSMENT OF THE GREENNESS OF TEACHING LABORATORY ACTIVITIES OF CHEMICAL SYNTHESIS IN PORTUGUES... more ASSESSMENT OF THE GREENNESS OF TEACHING LABORATORY ACTIVITIES OF CHEMICAL SYNTHESIS IN PORTUGUESE UNIVERSITIES
This article presents the results of a greenness assessment of chemical syntheses commonly used in university laboratories in Portuguese BSc degrees. The evaluation was performed using the Green Star holistic metric for separated evaluation of the reactio, isolation and purification steps (for evaluation of micro-greenness) as well as the global process, and was based on synthesis protocols found in the literature (all that could be reached). The results show that the protocols followed in Portugal have limited greenness, there existing almost always greener alternatives and that often the isolation and purification steps limit the process greenness. In favourable cases, greenness optimization can be achieved by combination of the greenest procedures for each step obtained from different protocols analyzed. The results show that a lot of efforts are required to reshape chemistry teaching towards Green Chemistry and Sustainability.
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Vânia G Zuin, Liliana Mammino (eds), Worldwide Trends in Green Chemistry Education, Chapter 8, p. 111-136., 2015
A review of the work that has been developed in Oporto on holistic metrics for evaluation of gree... more A review of the work that has been developed in Oporto on holistic metrics for evaluation of greenness in Green Chemistry is presented. As introduction, a discussion on the complex nature of chemistry, greenness and its evaluation is used to show: the systemic nature of the metrification problem; why reductionist one-dimensional metrics have to be used in batteries; and the advantage of adopting holistic metrics conceived under systems thinking. Then the following items are presented: first, conception and construction of simple graphic metrics based in the Twelve Principles of Green Chemistry for holistic assessment of the greenness: Green Star, Green Circle and Green Matrix; second, the use of the metrics for Green Chemistry teaching, especially of the Green Star, for greenness optimization of the synthesis used in organic and inorganic teaching laboratories and for evaluation of laboratory course contents in portuguese secondary schools; finally, a discussion of the advantages and limitations of holistic metrics based on the Twelve Principles.
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J. Chem. Educ., 91 (11), 1901–1908 (2014), Aug 25, 2014
Two graphic holistic metrics for assessing the greenness of synthesis, the “green star” and the “... more Two graphic holistic metrics for assessing the greenness of synthesis, the “green star” and the “green circle”, have been presented previously. These metrics assess the greenness by the degree of accomplishment of each of the 12 principles of green chemistry that apply to the case under evaluation. The criteria for assessment were based on the hazards symbols used in the system established by the European Union, directive 67/548/EEC, obtained from the safety data sheets of chemicals. Meanwhile, the Globally Harmonized System of Classification and Labeling of Chemicals (GHS) replaced that system and introduced a new classification of hazards and new symbols. The objective of this work is to present new criteria for the construction of the metrics based on the GHS system. A brief presentation of this system is included. The present upgrade also includes an improvement of the graphic presentation of the green star to facilitate the visual assessment of the degree of accomplishment of each green chemistry principle.
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Subtrópicos, 10, 6-7 (2014), 2014
Nesta entrevista discute-se a natureza holística da Química Verde e a necessidade de métricas hol... more Nesta entrevista discute-se a natureza holística da Química Verde e a necessidade de métricas holísticas para avaliação da verdura química.
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Quim. Nova, 37, 1085-1093 (2014), Jun 17, 2014
This article reports a study to increase the overall greenness of chemical syntheses for first-ye... more This article reports a study to increase the overall greenness of chemical syntheses for first-year university laboratories. The separate evaluation of the microgreenness of the three stages of synthesis (reaction, isolation and purification) using the Green Star (GS) was implemented and their respective contribution to overall greenness was investigated for two examples: syntheses of cobalt (III) tris(acetylacetonate) and potassium nitrilosulfonate. Results showed that the post-reaction (work-up) steps are the most problematic for overall greenness. Greenness optimization can be achieved by combining the greenest procedures for each step obtained from different protocols available in the literature.
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Quim. Nova, 37, 1094-1109 (2014), Jun 5, 2014
The use of a battery of three mass metrics (atomic economy - AE, reaction mass efficiency - RME, ... more The use of a battery of three mass metrics (atomic economy - AE, reaction mass efficiency - RME, and mass intensity - MI) for systemic evaluation of the material greenness of synthesis reactions is presented. Material greenness is discussed in terms of materialization/dematerialization of the reaction system and also according to the first two Principles of Green Chemistry, and is shown to involve two components: atomic greenness (incorporation of the atoms provided by reagents into the product, evaluated by AE and RME); and massic greenness (global mass of reagents and non-stoichiometric materials, evaluated by MI, related to the production of residues).
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Quim. Nova, 35, 1879-1883 (2012), Aug 24, 2012
New semi-quantitative metrics for simple evaluation of global greenness of chemical reactions use... more New semi-quantitative metrics for simple evaluation of global greenness of chemical reactions used in teaching laboratories, namely, the Green Circle (GC) and Green Matrix (GM), were developed. These metrics globally consider all Twelve Principles of Green Chemistry. To illustrate their construction, the greenness of several syntheses performed in the laboratory under different sets of conditions was assessed. The tools were validated by comparing the results with another metric, the Green Star (GS), developed in our previous study. Results showed these new metrics were useful for the intended purpose, having the advantage of being simpler than the GS.
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Quim. Nova, 35, 1250-1259 (2012), Mar 23, 2012
The second 12 principles of Green Chemistry (Winterton, 2001) are presented and discussed to show... more The second 12 principles of Green Chemistry (Winterton, 2001) are presented and discussed to show how they press academic chemists to focus the invention of synthetic pathways more directly on industrial process development, allowing a quicker progress along the greenness chain and a softer implementation of Green Chemistry in the industrial practice of chemistry. The relationships between the two sets of principles are tentatively established and discussed to make easier their joint use. The net of connections shows the systemic nature of Green Chemistry.
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Quím. Nova, 34, 535-543 (2011), Jan 26, 2011
An analysis of the activities that contributed to the birth of Green Chemistry (GC) about twenty ... more An analysis of the activities that contributed to the birth of Green Chemistry (GC) about twenty years ago has shown that it emerged in response to the problems of pollution and wastes felt by the Chemical Industry. This close connection between GC and the Chemical Industry is similar to that found earlier between Chemistry and Industrial Chemistry before they separated. It was also found that since its very beginning the Chemical Industry has occasionally practiced GC. Broad implications of these findings to the teaching of GC are discussed.
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Quim. Nova, 34, 535-543 (2011), Jan 26, 2011
An analysis of the activities that contributed to the birth of Green Chemistry (GC) about twenty ... more An analysis of the activities that contributed to the birth of Green Chemistry (GC) about twenty years ago has shown that it emerged in response to the problems of pollution and wastes felt by the Chemical Industry. This close connection between GC and the Chemical Industry is similar to that found earlier between Chemistry and Industrial Chemistry before they separated. It was also found that since its very beginning the Chemical Industry has occasionally practiced GC. Broad implications of these findings to the teaching of GC are discussed.
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Quím. Nova, 34, 1862-1868 (2011), Jun 10, 2011
A comparative study of a convergent and the linear synthetic pathway with respect to their relati... more A comparative study of a convergent and the linear synthetic pathway with respect to their relative greenish allowed the quantification of the advantages of the former with respect to atomic productivity as well as robustness. The calculations show that convergent pathways provide a decrease of costs together with a decrease of E factor and an increase of atomic economy which means that greenish is accompanied by an economic advantage. The influence of other features of the convergent pathways synthesis on the improvement of the synthesis greenish is discussed qualitatively.
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Quim. Nova, 34, 1291-1297 (2011), Mar 29, 2011
The role of the logistics in the design of synthetic pathways aimed at greenish is discussed. The... more The role of the logistics in the design of synthetic pathways aimed at greenish is discussed. The inluence on costs (of reagents, solvents and total), as well as on atomic productivity green metrics (atomic economy and E factor), of the position along the pathway of a step with low yield, or involving high dilution of the reagents or expensive reagents, has been evaluated by calculations on a linear pathway model. The results show the economic importance of Green Chemistry and provide useful information for pathway design or improvement.
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Quím. Nova, 33, 759-764 (2010), Mar 10, 2010
A new semi-quantitative metrics, Green Star (GS), for evaluation of the global greenishness of ch... more A new semi-quantitative metrics, Green Star (GS), for evaluation of the global greenishness of chemical reactions used in teaching laboratories has been developed. Its aim is to help choosing the more acceptable reactions for implementing Green Chemistry (GC) and to identify suitable modifications of reaction protocols to improve the greenishness of chemistry. GS considers globally all the Twelve Principles of GC. To illustrate its construction, the tetraamminecopper(II) sulfate monohydrate laboratory synthesis, performed under several sets of conditions to pursue greenishness, is presented. A comparative study with other GC metrics showed the advantages of GS and that it accomplishes its purpose.
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BOOKS by Adelio A S C Machado
Preface, Prologue. 1 - Introduction to Metrics. 2 - Mass Metrics. 3 - Holistic Metrics. Conclusion. References. (254 p.)
GREEN CHEMISTRY by Adelio A S C Machado
This paper analyses 286 papers on Green Chemistry published in the Journal of Chemical Education regarding the relationships between Green Chemistry, Sustainability and Systems Thinking present in teaching approaches.
An analysis of the recent inclusion of Green Chemistry in the syllabus of Physics and Chemistry A of secondary education (grade 11), focused on the treatment of the atom economy, in the programmatic text of the Ministry of Education and the six certified textbooks for the discipline is described. It was found that the subject was introduced with insufficient detail in the syllabus proposal, which is diffuse and erroneous. For instance, it ignores that the term atom economy is used for both a concept and a greenness metric and that the mass metrification of synthetic reactions requires other metrics. The treatment given to the subject in the proposal probably contributed for the differences found in its development in the textbooks and for the problematic/erroneous statements they include. This situation requires clarification and therefore a global treatment of the metrification of the mass greenness of the use of matter in chemical reactions is included, as well as a very simple example, the synthesis of tin(IV) iodide, to help understanding the different features of greenness captured by each metric.
The bibliography on the conception of the Green Chemistry mass metric called Atom Economy (AE) was thoroughly reviewed. The authorship of this metric has been commonly attributed to the academic chemist Barry Trost in sequence of its presentation of the Atom Economy qualitative concept, but the analysis of the literature shows that its author was Roger Sheldon, who calculated the metric before, in an industrial synthesis context, calling it Atom Utilization (AU). The origin of this imprecision is discussed, as well as the influence of the different professional contexts of the two chemists (academic vs. industrial) on their mindset for visualization of the Atom Economy idea and calculation of the corresponding metric.
An analysis of the usefulness of the Twelve Principles (Anastas and Warner) and the Second Twelve Principles (Winterton) of Green Chemistry (GC) for supporting the teaching of Laboratory Safety (LS) has been developed. An assessment of the contents of both groups of principles that are relevant for LS, their scope, ways of application, etc., is presented, followed by a brief discussion on approaches suitable for their use in teaching. The discussion suggests that the Twelve Principles, being generic and intuitive prescriptions, may support procedures for the introduction of the teaching of LS in the first years of university degrees and in secondary schools, while the use of the Second Twelve Principles is more problematic, seeming more suitable for advanced years of university courses, as they refer to more specific aspects of the implementation of chemistry. In both cases, the aim will be acquiring synergies with a LS and GC integrated teaching. Laterally the analysis showed that these teaching procedures were suitable for including a discussion of the Twelve Principles limitations, some of which emerged from a global view of the results. The huge complexities of chemistry, GC, chemical hazards, etc., and their implications on the LS teaching are also briefly considered, pointing to the urgency of adopting a systemic, instead of the current reductionist mindset used in chemistry education, to deal with the required reshaping of chemical safety teaching and practice.
This article presents the results of a greenness assessment of chemical syntheses commonly used in university laboratories in Portuguese BSc degrees. The evaluation was performed using the Green Star holistic metric for separated evaluation of the reactio, isolation and purification steps (for evaluation of micro-greenness) as well as the global process, and was based on synthesis protocols found in the literature (all that could be reached). The results show that the protocols followed in Portugal have limited greenness, there existing almost always greener alternatives and that often the isolation and purification steps limit the process greenness. In favourable cases, greenness optimization can be achieved by combination of the greenest procedures for each step obtained from different protocols analyzed. The results show that a lot of efforts are required to reshape chemistry teaching towards Green Chemistry and Sustainability.
Preface, Prologue. 1 - Introduction to Metrics. 2 - Mass Metrics. 3 - Holistic Metrics. Conclusion. References. (254 p.)
This paper analyses 286 papers on Green Chemistry published in the Journal of Chemical Education regarding the relationships between Green Chemistry, Sustainability and Systems Thinking present in teaching approaches.
An analysis of the recent inclusion of Green Chemistry in the syllabus of Physics and Chemistry A of secondary education (grade 11), focused on the treatment of the atom economy, in the programmatic text of the Ministry of Education and the six certified textbooks for the discipline is described. It was found that the subject was introduced with insufficient detail in the syllabus proposal, which is diffuse and erroneous. For instance, it ignores that the term atom economy is used for both a concept and a greenness metric and that the mass metrification of synthetic reactions requires other metrics. The treatment given to the subject in the proposal probably contributed for the differences found in its development in the textbooks and for the problematic/erroneous statements they include. This situation requires clarification and therefore a global treatment of the metrification of the mass greenness of the use of matter in chemical reactions is included, as well as a very simple example, the synthesis of tin(IV) iodide, to help understanding the different features of greenness captured by each metric.
The bibliography on the conception of the Green Chemistry mass metric called Atom Economy (AE) was thoroughly reviewed. The authorship of this metric has been commonly attributed to the academic chemist Barry Trost in sequence of its presentation of the Atom Economy qualitative concept, but the analysis of the literature shows that its author was Roger Sheldon, who calculated the metric before, in an industrial synthesis context, calling it Atom Utilization (AU). The origin of this imprecision is discussed, as well as the influence of the different professional contexts of the two chemists (academic vs. industrial) on their mindset for visualization of the Atom Economy idea and calculation of the corresponding metric.
An analysis of the usefulness of the Twelve Principles (Anastas and Warner) and the Second Twelve Principles (Winterton) of Green Chemistry (GC) for supporting the teaching of Laboratory Safety (LS) has been developed. An assessment of the contents of both groups of principles that are relevant for LS, their scope, ways of application, etc., is presented, followed by a brief discussion on approaches suitable for their use in teaching. The discussion suggests that the Twelve Principles, being generic and intuitive prescriptions, may support procedures for the introduction of the teaching of LS in the first years of university degrees and in secondary schools, while the use of the Second Twelve Principles is more problematic, seeming more suitable for advanced years of university courses, as they refer to more specific aspects of the implementation of chemistry. In both cases, the aim will be acquiring synergies with a LS and GC integrated teaching. Laterally the analysis showed that these teaching procedures were suitable for including a discussion of the Twelve Principles limitations, some of which emerged from a global view of the results. The huge complexities of chemistry, GC, chemical hazards, etc., and their implications on the LS teaching are also briefly considered, pointing to the urgency of adopting a systemic, instead of the current reductionist mindset used in chemistry education, to deal with the required reshaping of chemical safety teaching and practice.
This article presents the results of a greenness assessment of chemical syntheses commonly used in university laboratories in Portuguese BSc degrees. The evaluation was performed using the Green Star holistic metric for separated evaluation of the reactio, isolation and purification steps (for evaluation of micro-greenness) as well as the global process, and was based on synthesis protocols found in the literature (all that could be reached). The results show that the protocols followed in Portugal have limited greenness, there existing almost always greener alternatives and that often the isolation and purification steps limit the process greenness. In favourable cases, greenness optimization can be achieved by combination of the greenest procedures for each step obtained from different protocols analyzed. The results show that a lot of efforts are required to reshape chemistry teaching towards Green Chemistry and Sustainability.
Risco = f (exposição, perigos)
Em consequência do silêncio das métricas de QV, a variação da escala faz emergir a necessidade de conceber métricas específicas para a avaliação de verdura mediante aferição do risco, que terão de envolver a exposição. Assim, apresenta-se o design de uma métrica para avaliar as vantagens da microescala, em experiências laboratoriais no contexto educacional, que usa as massas de reagentes (mi em gramas), o tempo de exposição (t em horas) e os perigos para a saúde, ambiente e físicos associados aos mesmos, para calcular um índice de risco dependente da escala (Scale Risk Index – SRI),
SRI = t (∑pSi.mi + ∑pAi.mi + ∑pFi.mi)
onde pSi, pAi e pFi são as pontuações dos perigos para a saúde, ambiente e físicos das substâncias envolvidas, definidas de acordo com critérios estabelecidos a priori.
A métrica foi testada em várias sínteses, tanto orgânicas como inorgânicas, de que serão discutidos exemplos, apresentando sempre valores menores a microescala que a macroescala (métrica inversa de verdura). Em suma, o SRI revela-se eficaz para distinguir os impactos da micro e da macroescala, uma vez que captura a variação da exposição às substâncias com a escala, além dos seus perigos.
Referências
[1] Singh, M.M.; Szafran, Z.; Pike, R.M. J. Chem. Educ. 1999, 76, 1684-1686.
[2] Szafran, Z.; Singh, M.M.; Pike, R.M. Educ. Quím. 2000, 1, 172-173.
[3] Ribeiro, M.G.T.C.; Costa, D.A.; Machado, A.A.S.C. Quím. Nova 2010, 33, 759-764.
[4] Ribeiro, M.G.T.C.; Costa, D.A.; Machado, A.A.S.C. Green Chem. Lett. Rev. 2010, 3, 149-159.
[5] Ribeiro, M.G.T.C.; Yunes, S.F.; Machado, A.A.S.C. J. Chem. Educ., 2014, ID ed-2013-00421b.R1.
[6] Ribeiro, M.G.T.C.; Machado, A.A.S.C. J. Chem. Educ. 2011, 88, 947-953.
A análise revelou que os protocolos que envolvem arrastamento de vapor, mas usam solventes orgânicos no work-up, apresentam verdura reduzida devido aos perigos para a saúde humana e ambiente associados aos solventes (pentano, éter de petróleo e diclorometano). O procedimento que prescinde de solventes no work-up revelou-se o mais verde e foi o escolhido para trabalho experimental.
O estudo demonstrou a importância da análise da verdura química baseada quer em métricas quantitativas clássicas (e.g. Fator E), quer em métricas quantitativas mais ligadas à atividade industrial, mas com interesse no ensino laboratorial da QV, pois captam facetas importantes da verdura (Throughput, Intensidade de energia, EI, e Intensidade de tempo, TI), quer em métricas holísticas como a EV [2-3]. Estas métricas, usadas em paralelo como um sistema de metrificação, permitem uma visão mais global e realista da verdura.
O uso deste tipo de metodologia, se adotada na realização experimental da extração de óleo de laranja no ensino secundário e universitário, permite uma discussão da verdura química com alcance amplo e bastante formativa no ensino da QV. Em particular, evidencia a complexidade da verdura química e da própria QV – a variedade de aspetos em consideração, quando se pretende reformatar a prática da química para a QV, exige raciocínio sistémico para lidar com a multidimensionalidade dos problemas.
Referências
[1] Lin, C. S. K.; et al., Food waste as a valuable resource for the production of chemicals, materials and fuels. Current situation and global perspective. Energy Environ. Sci. 2013, 6 (2), 426-464.
[2] Ribeiro, M. G. T. C.; et al., ‘‘Green Star’’: a holistic Green Chemistry metric for evaluation of teaching laboratory experiments. Green Chem. Lett. Rev. 2010, 3 (2), 149-159.
[3] Ribeiro, M. G. T. C.; et al., Assessing the Greenness of Chemical Reactions in the Laboratory Using Updated Holistic Graphic Metrics Based on the Globally Harmonized System of Classification and Labeling of Chemicals. J. Chem. Ed. 2014, in press.
A síntese do cloreto de 1-hexil-3-metilimidazólio ([C6MIM]Cl) foi otimizada a partir de um protocolo da literatura educacional (A) [3], que sugere a utilização de dois solventes (água e éter dietílico) na fase de work-up. A otimização implicou a eliminação de um deles (água) que, apesar de inócuo, revelou-se pouco eficiente (baixa pureza do produto) e teve impacto negativo nas métricas de energia e tempo, dando origem a um protocolo revisto (B). A avaliação do outro solvente (éter dietílico) revelou que este apresenta baixa verdura (elevado perigo físico e perigo moderado para a saúde humana), pelo que foi substituído por um com maior verdura intrínseca, o acetato de etilo (protocolo C). Contudo, a substituição teve um impacto negativo nas métricas de energia e tempo relativamente ao protocolo B.
Estes resultados revelam o desafio na escolha de solvente quanto à ponderação entre a maior verdura do solvente, o mais eficiente e o que permite obter melhores métricas (energia e tempo, no caso em estudo). A utilização de solventes com maior verdura pode revelar-se pouco eficiente e apresentar consequências negativas nas métricas, enquanto que um solvente mais eficiente pode ser pouco verde, se apresentar perigos elevados para a saúde humana e ambiente. Esta situação evidencia uma vez mais a natureza holística da QV, cuja implementação exige otimizações e tomadas de decisão multidimensionais, no quadro da ciência sistémica, em resultado da complexidade quer da química, quer da verdura.
Referências
[1] Capello, C.; Fischer, U.; Hungerbuhler, K., What is a green solvent? A comprehensive framework for the environmental assessment of solvents. Green Chem. 2007, 9 (9), 927-934.
[2] Kerton, F., Alternative Solvents for Green Chemistry. The Royal Society of Chemistry: 2009.
[3] Stark, A.; Ott, D.; Kralisch, D.; Kreisel, G.; Ondruschka, B., Ionic Liquids and Green Chemistry: A Lab Experiment. J. Chem. Ed. 2010, 87 (2), 196-201.
The purpose of this communication is to present the results of a study for characterizing the opinion of Brazilian chemistry researchers from the National Council for Scientific and Technological Development (CNPq) on the meaning and scope of the terms Environmental Sustainability (ES) and Sustainable Development (SD) in chemistry.
The final aim of the study is to find how chemistry researchers feel about providing Sustainability with respect to the environment when the fragility and limits of this are taken into account. This is important to understand the response chemistry may provide to these challenges, especially when the variety of contributions allowed by Green Chemistry (GC) are considered.
RESULTS AND DISCUSSION
The study consisted of an on-line questionnaire based on short texts on concepts and situations connected to SD and ES followed by nine groups of Questions (Q1-9) about the degree of agreement/disagreement on them. The Brundtland definition was used as a departure point (Q1), but the scope of the concept was broadened to include other formulations anchored in other areas of knowledge (biology, economics, etc.) (Q2), and different scenarios and implications on an environmental equilibrium state were also considered (Q3). The contradiction between the world limited resources and a continuous growth was explored in Q4 and led to questions on the effects on ES of the principles of matter and energy conservation, the 2nd Law of Thermodynamics (Q5), and consequences on how to deal with pollutants (Q6 to Q8), to search whether procedures based on risk (“risk paradigm”) are considered to be sufficient to resolve the problems or a new paradigm (“ecological paradigm”) (1) is desirable.
The questionnaire was sent to 456 researchers and 82 replies were received.
A majority of this group (ca. 82%) fully agrees with the conception of SD/Sustainability of the Brundtland Commission, considered sufficient and efficient to define the concepts. However, when other visions of the concepts such as those of biology, economics, etc, were considered, the group showed divisions on the degree of agreement, but strangely no mentions were advanced to the physical limits to Sustainability imposed by nature, as a consequence of the postulates of Thermodynamics.
CONCLUSION
The responses show awareness of the requirement of a more sustainable development model with respect to the limits imposed by the environment, although with no consensus about the nature and strength of these limits. Indeed, although the respondents recognize the limits of the classic “risk paradigm” that has been followed for environmental control, they were divided over the need for and the characteristics of the new "ecological paradigm" that fully supports the ES, as well as GC – indeed it is expressed in the 12 Principles.
The study will be continued by an analysis of the relations between the researchers’ responses and fields of work (shown by scientific papers), to try to understand how these influence their mindsets on ES.
ACKNOWLEDGEMENTS
To CNPq and CAPES Foundation (Brasil), and FCT (Portugal) for the award of a collaboration project (289/11-Brasil and 151/11-Portugal) on “Chemical Education under the Perspective of GC and ES”.
REFERENCES
1. J. Thornton, Beyond Risk: An Ecological Paradigm to Prevent Global Chemical Pollution, Int. J. Occup. Environ. Health, 6 (2000) 318-330
Esta comunicação decorre de um projecto em curso que tem como objectivo avaliar se há, ou não, ganhos de verdura quando se passa da macro para a microescala, referindo-se à síntese do acetato de n-butilo (a preparação de ésteres faz parte dos programas de Química do Ensino Secundário), para a qual a influência da escala na verdura atómica foi avaliada por diversas métricas [2]: métricas de massa ou de produtividade atómica, já que se tem vindo a desenvolver esforços de qualificar o seu funcionamento – factor E, intensidade de massa (MI), utilização atómica percentual (AU), eficiência de massa relativa (RME) e eficiência de carbono percentual (CEE); e a métrica holística ESTRELA VERDE [3-5].
Métricas (Média, DP) (n=4)
Macroescala/Microescala
Rendimento, %: 80,4±1,8/58,1±3,0
E-factor: 0,91±0,0/ 2,1±0,2
M:I 1,91±/3,1±0,2
RME, % = AU, %: 69,0±1,6/49,9±2,5
CEE, %: 79,9±1,8/57,8±2,9
As sínteses foram realizadas em condições quase estequiométricas (excesso de 1,9% de ácido acético) utilizando-se Dowex 50W×2–100 (Sigma-Aldrich) como catalisador [6]. Na realização a microescala a redução de escala foi de 1/10 (199 →19,9 mmol de butanol).
Os resultados mostram que todas as métricas de massa calculadas (água excluída) indicam uma perda de verdura atómica a microescala. Isto deve-se à diminuição do rendimento, que resulta das perdas de produto ocorridas durante o seu isolamento, mais relevantes a microescala, devido às pequenas quantidades dele. Por outro lado, a EV manteve-se igual (IPE = 26, um valor que evidencia verdura limitada), pelo que os resultados das métricas são contraditórios.
Este resultado não é inesperado, porque na microescala se reduzem as quantidades de substâncias e os tempos de reacção, pelo que a diminuição do risco (= perigosidade x exposição) resulta da diminuição da exposição, não da perigosidade – as vantagens são obtidas no âmbito do velho paradigma do risco, não do paradigma ecológico em que a QV é suportada. Ganha-se verdura, já que se reduzem os riscos para a saúde e de acidente e os resíduos, mas ela é de “tipo clássico” (via exposição).
Em suma, a utilização da microescala nos laboratórios educacionais tem vantagens óbvias, mas o uso das métricas vigentes da QV para comparar os ganhos de verdura não os detecta, dada a sua diferente natureza – será necessária uma nova métrica capaz de aferir a verdura nesta situação.
Referências
[1] M. M. Singh, Z. Szafran e R. M. Pike, J. Chem. Educ 76 (1999) 1684.
[2] A. Lapkin and D. Constable (eds.), Green Chemistry Metrics – Measuring and Monitoring Sustainable Processes, Wiley, 2009.
[3] M. G. T. C. Ribeiro, D. A. Costa e A. A. S. C. Machado, Green Chem. Lett. and Rev. 3 (2010) 149-159.
[4] M. G. T. C. Ribeiro, D. A. Costa e A. A. S. C. Machado, Química Nova 33 (2010) 759-764.
[5] M. G. T. C. Ribeiro e A. A. S. C. Machado, J. Chem. Ed. (2011) DOI: 10.1021/ed100174f.
[6] K. L. Williamson, R. D. Minard e K. M. Masters, Macroscale and Microscale Organic Experiments, Houghton Mifflin Co, Boston, 2007.
Trabalho em curso que envolveu uma análise global destas métricas [3-5] evidenciou que os seus valores dependiam da estequiometria das reacções de síntese e das condições de realização destas – o que pode limitar o alcance da sua utilidade para comparar a verdura das sínteses, um facto aparentemente ignorado na literatura. Esta situação é aqui ilustrada com as sínteses laboratoriais do tris(acetilacetonato)ferro(III) e do oxalato de ferro(II) diidratado, que foram repetidas em diversas condições, com registo rigoroso das massas dos reagentes, produtos, solventes, etc. (como aconselhado por Winterton [6]), para investigar a influência das condições da reacção (rendimento, excesso de um reagente estequiométrico, etc.) nos valores da métrica Eficiência de Massa Relativa (RME).
Por via teórica, a RME foi expressa como uma função bidimensional do rendimento (y) e do excesso do ligando (x), segundo RME = k1 y/(k2 + k3 x), com os kj calculados a partir dos coeficentes estequiométricos e massas molares. Nas Figs. apresentam-se os gráficos das superficies geradas por estas funções e os valores experimentais coligidos nas experiências, que mostram bom acordo. A forma das superfícies é semelhante, mas com diferente inclinação, devido a diferenças nos coeficientes estequiométricos (reacções 1:3 e 1:1, respectivamente) e nas massas molares dos compostos envolvidos nas duas reacções – facto que evidencia não ser lícita a comparação directa de métricas para reacções diferentes.
Agradecimentos: Às estagiárias Olga Martins e Salomé Fernandes, apoio no trabalho laboratorial.
Referências
[1] A. Lapkin and D. Constable (eds.), Green Chemistry Metrics – Measuring and Monitoring Sustainable Processes, Wiley, 2009.
[2] P. T. Anastas and J. C. Warner, Green Chemistry – Theory and Practice, Oxford UP, 1998, p. 30.
[3] M. G. T. C. Ribeiro, D. A. Costa and A. A. S. C. Machado, Green Chem. Lett. and Rev. 3 (2010) 149-159.
[4] M. G. T. C. Ribeiro, D. A. Costa and A. A. S. C. Machado, Química Nova 33 (2010) 759-764.
[5] M. G. T. C. Ribeiro and A. A. S. C. Machado, J. Chem. Ed. (2011) DOI: 10.1021/ed100174f.
[6] N. Winterton, Green Chem. 3 (2001) G73-G75.
A análise SWOT, criada na Harvard Business School nos anos sessenta, embora tenha sido originalmente utilizada na avaliação empresarial, é aplicada actualmente nas mais diversas áreas, tendo recentemente chegado à química [2]. O termo SWOT resulta das iniciais S (Strenghts – pontos fortes), W (Weaknenesses – pontos fracos), O (Opportunities – oportunidades) e T (Threats – ameaças). Os pontos fortes indicam os aspectos positivos, e os fracos os negativos, relativamente aos objectivos a atingir e o seu conjunto corresponde à análise interna. As oportunidades podem tornar mais forte o objecto em análise e as ameaças pôr em causa o seu sucesso; o seu conjunto corresponde à análise externa. Para se realizar o SWOT começa-se por definir as dimensões destas duas análises.
Os resultados da análise SWOT mostraram que as experiências programadas não suportam o ensino CTS2. Por exemplo, o gráfico na Fig. 1 permite concluir que 70% das actividades laboratoriais do 10º e 11º anos apresentam 40% ou mais de pontos fracos. Por outro lado, uma fracção apreciável dos pontos fortes não eram satisfeitos por mais de 80% das experiências.
Em suma, a adopção da postura CTS2, que presentemente se impõe, exigirá profundas alterações dos programas actuais.
Referências
[1] G. Aikenhead, What is STS science teaching?, in J. Solomon e G. Aikenhead (eds), STS Education – International Perspectives on Reform, TCP, 1994, 47-59.
[2] M. Deetlefs, K. R. Seddon, Green Chemistry, 12 (2010) 17-30.
Esta comunicação tem como objectivo apresentar resultados deste estudo, que revelou que muitas das experiências laboratoriais prescritas no referido programa não são adequadas para integrar o ensino da química no âmbito do paradigma da QV.
No gráfico apresenta-se o número de experiências com IPE (índice indicativo da verdura, máximo 100 %) nos intervalos indicados. O gráfico mostra que 75 % do conjunto das actividades laboratoriais do 10º e 11º anos apresentaram uma verdura baixa, ou seja, envolvem aspectos negativos quanto a segurança e riscos, nomeadamente dos reagentes usados, o que aponta para a necessidade da sua revisão.
Referências
(1) Lapkin, A.; Constable, D., Green Chemistry Metric - Measuring and Monitoring Sustainable Processes, Wiley, 2008.
(2) Ribeiro, M. G. T. C.; Costa, D. A.; Machado, A. A. S. C. Quím. Nova 2010, 33, 759.
(3) Ribeiro, M. G. T. C.; Costa, D. A.; Machado, A. A. S. C. Green Chem. Let. & Rev. 2010, 3, 149.
Neste contexto, iniciou-se neste Departamento uma linha de actividade dirigida à implementação do ensino da QV no ensino secundário. Para instilar nos estudantes a nova mentalidade de praticar a química, o ensino experimental desta deve adoptar experiências que envolvam intencionalmente como objectivo o aumento da verdura e que evidenciem como é possível concretizá-lo por meio da realização paralela de versões tradicionais e com verdura acrescida. Para implementação da QV é necessário realizar a aferição da verdura, uma grandeza muito complexa, cuja avaliação passa pela utilização de ferramentas e métricas apropriadas (p.ex. [1]).
Para utilização simples a nível elementar, para avaliação da verdura das experiências de química, nomeadamente de reacções químicas, tem-se em construção uma nova métrica semiquantitativa, gráfica, a chamada “Estrela Verde” (“GreenStar”), na qual se consideram globalmente os Doze Princípios da QV [2]. A métrica consiste em avaliar a verdura referente a cada um destes, numa escala de 1 a 3, por meio de critérios pré-definidos e representar os resultados num gráfico de estrela (quanto mais cheia for a estrela, maior é a verdura).
A Estrela Verde será exemplificada pela análise da verdura da síntese laboratorial do sulfato de tetraminocobre(II), que faz parte do programa actual da disciplina de Física e Química do 11º ano do Ensino Secundário (é a única experiência de química preparativa realizada no 10º e 11º anos) em função do modo como é realizada (macro/microescala) e tendo em vista a sua “optimização verde”.
Os resultados serão comparados com os obtidos pela EcoScale, uma outra métrica recentemente introduzida com o mesmo fim de avaliar as experiências de síntese no laboratório [3].
Referências
[1] A. A. S. C. Machado, Métricas da Química Verde – A Produtividade Atómica, QUIMICA 107 (2007) 47-55.
[2] P. T. Anastas e J. C. Warner, Green Chemistry, Oxford UP, 1998, p. 30.
[3] K. van Aken, L. Strekowski e L. Patiny, EcoScale, a Semi-quantitative Tool to Select an Organic Preparation Based on Economical and Ecological Parameters, Beilstein J. Org. Chem. 2(3) (2006) 1-7.
Palavras-Chave: Princípio da precaução; Incerteza científica; Alfabetização científica e tecnológica; Tomada de decisão participativa.
Abstract: Assessing risk situations and avoiding social and environmental impacts from science and technology is what underlies the precautionary approaches. To identify how academic productions in the science teaching area discuss the Precautionary Principle in education, we carried out a bibliographic survey in Brazilian and international journals in this area, which showed the existence of works that highlight its importance for training science students for citizenship. However, few papers deal with this theme or propose ways to insert it in teaching. When considering these aspects we aim to find ways for using the principle in decision making in situations involving scientific uncertainty.
Keywords: Precautionary principle; Scientific uncertainty; Scientific and technological literacy; Participatory decision-making.
O objectivo deste texto é proporcionar uma visão global e genérica da postura do STS do ensino da ciência. O texto começa por uma breve apresentação da postura e, depois, discute, a título de exemplo, algumas das múltiplas interrelações em jogo entre a ciência, a tecnologia e a sociedade; refere a seguir algumas observações sobre a importância das “questões” na STS (e não só), terminando com uma referência a algumas designações alternativas à STS que sugiram na sua esteira, além de STSS (ou STS2): STSE (de “Science, Technology, Society and Environment”), e STSEE ou STSE2 (de de Science, Technology, Society, Environment and Energy”).
sistemático. Os nomes dados pelos “nomenclaturistas” profissionais parecem muitas vezes estranhos e a sua interpretação é complexa. Uma parte do esforço da União Internacional de Química Puro e Aplicada (IUPAC) de revisão das regras de nomenclatura, de forma a facilitar a dedução das estruturas a partir dos nomes, é criar um conjunto coerente de re gras aplicável tanto às substâncias inorgânicas, como às orgânicas e organometálicas. Para apresentar as mesmas de uma forma clqra e simples, introduziram-se novos termos, tais como por exemplo hidreto parental, composto parental funcional, descritor, nomenclatura aditiva, nomenclatura substitutiva e nomenclatura permutativa. Mas estas palavras corresponderão apenas a “vinho velho em odres novos” ou a conceitos novos definidos com maior rigor e amplitude que os antigos?
Os méritos de cada sistema de nomenclatura revelam-se sobretudo na facilidade com que se deduz a estrutura de cada substância a partir do seu nome. Para facilitar este processo, um passo fundamental é identificar o sistema segundo o qual foi atribuído o nome. Por isso, torna-se cada vez mais importante saber distinguir entre os sistemas substitutivo e aditivo, e conhecer as suas regras e domínios de aplicação. Para a nomenclatura substitutiva, inicialmente desenvolvida para a Química Orgânica, também é indispensável saber o que é um hidreto parental e um composto parental funcional, bem como conhecer a diferença entre nomenclatura substitutiva e permutativa. A nomenclatura aditiva, por sua vez, resultou duma ampliação do método e do domínio de aplicação do sistema de nomenclatura da química de coordenação, criado por Werner. Nos compostos organometálicos e outros em que existem um ou mais átomos centrais, aparecem cada vez mais exemplos em que se usa simultaneamente as nomenclaturas aditiva e substitutiva. Nesses casos, é essencial saber identificar as partes do nome resultantes da aplicação de um e possível através do conhecimento rigoroso destes conceitos.
Keywords: Urea potentiometric biosensor; Urease; Chitosan membrane; Blood serum
Os eléctrodos construídos têm características de funcionamento perfeitamente competitivas com as dos eléctrodos selectivos comerciais das séries Orion 94-00-A e Philips IS550 sensíveis aos respectivos halogenetos.
The temperature-dependence of the Mossbauer parameters has been used to derive information about the distortions from octahedral symmetry and it is concluded that the dimensions of the crystal-line lattice are changing slightly with temperature.
obtained from equilibrium constants and mass, proton and charge balances
F( H3O+, equilibrium constants) = 0
using chemical simplifications. The errors involved in these simplifications were assessed and controlled for each case (acid, base or mixture) to obtain formulae with values of pH with errors less than 0.01, 0.02 and 0.03, depending on the complexity of the case. The simplifications used can be tested for each calculation for confirmation of the validity of the calculated pH.
pH = (1/2) (pKaA + pKbB)
has been studied by computation. The use of the formula
pH = (1/2) (pKaA + pKbB) - log [(a + KbB ) / (a + KaA)]
has also been considered. Diagrams indicating the conditions where the formulae give the pH value with error less than 0.05 have been obtained. The symmetry of the system is discussed.