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DOI: 10.1039/C2RP90002E (Paper) Chem. Educ. Res. Pract., 2012, 13, 103-111

Sustainable production of chemicals – an educational perspective†‡

Marco Eissen *
Gymnasium Ganderkesee, Am Steinacker 12, 27777 Ganderkesee, Germany. E-mail: marco.eissen@web.de; Tel: +49 4222 920197

Received 15th September 2011 , Accepted 14th February 2012

First published on 21st March 2012

Abstract

Sustainability is a very general term and the question arises how to specify it within daily laboratory work. In this regard, appropriate metrics could support a socially acceptable, ecological and economic product development. The application of metrics for sustainability should be strengthened in education, because they do not belong to standard considerations in synthesis design so far. This article describes educational material (online resource) designated to students and chemists who are willing to quantify the benefits of green chemistry in the lab and to search for an optimization potential. As an example, bromination reactions are compared by considering mass balance, raw material costs and qualitative aspects such as, e.g., toxicology and combustibility. While keeping in mind the three dimensions of sustainability – economy, environment and social affairs – the idea of the concept of sustainable chemistry, i.e., green chemistry, takes shape in daily laboratory work.

Introduction

In the educational literature a couple of suggestions are made how metrics can be applied in synthesis design to let green chemistry become a habit of mind (Table 1). The term ‘metric’ denotes a ratio or number which indicates the performance of an object of study.
Table 1 Application of metrics in chemistry education literature
Chemical synthesis Metrics Literature
AEa Eb other
a Atom economy (Trost, 1991, Eissen et al., 2004b). b Environmental factor (Sheldon, 1994).
Bromination ✓ ✓ ✓ (McKenzie et al., 2005)
Nitrosation ✓ ✓ ✓ (Van Arnum, 2005)
Grignard (and many others) ✓ ✓ ✓ (Andraos and Sayed, 2007)
Friedel–Crafts   ✓ (✓) (Ranke et al., 2008)
Suzuki ✓     (Aktoudianakis et al., 2008)
Biginelli ✓     (Aktoudianakis et al., 2009)
Pechmann condensation ✓ ✓   (Young et al., 2010)
Ionic liquids ✓ ✓ ✓ (Stark et al., 2010)
Metal-acetylacetonate ✓ ✓ ✓ (Ribeiro and Machado, 2011)

Whereas the concept of atom economy (AE) (Trost, 1991, Eissen et al., 2004b) takes only a look at the efficiency of the reaction stoichiometry, the environmental factor (E-factor; Sheldon, 1994; relation waste/product) which is similar to the mass intensity (MI; Constable et al., 2002; relation raw material/product) considers all substance masses. As mass intensity does not correlate with atom economy, the latter alone will not deliver the desired ‘cleaner’ process (Curzons et al., 2001). In this regard it is noteworthy that two of the listed examples (Table 1) admittedly use the label ‘green’ in the article title, but confine themselves to atom economy and ignore catalyst and solvent amounts. Apparently, calculations that go beyond atom economy necessitate a certain expenditure. This might be a reason for a preferred reference in professional literature to rather qualitative criteria (if at all) such as the twelve principles of green chemistry (Anastas and Warner, 1998) than to substantiate (Andraos, 2009) claims of ‘greenness’ with some kind of metrics analysis, i.e., to substantiate the validity of the principles (Winterton, 2001). E.g., efficiency of prinicple 9 by Anastas and Warner (1998) “Catalytic reagents are superior to stoichiometric reagents” can simply be expressed (together with principles 2 and 8) by the E-factor because the amount of (catalyst, etc.) waste objectively and comparable reflects the efficiency of (alternative) syntheses (Eissen et al., 2003a). The industrial efforts for both environmental protection and economic profitability by means of production-integrated measures assembled to a conceptional picture around 1990 (Wiesner et al., 1995) and principles partly being similar to the green chemistry ones were formulated. In academia, however, a green look on chemical synthesis that rests upon a quantitative assessment seems to have increasingly emerged only recently (Table 2). Regarding a so-called life cycle assessment (systematic analysis of the environmental impacts of products during their total lifespan), efforts for its integration are even sparser because much more information, e.g., concerning energy demand, have to be collected and interpreted.

Table 2 Application of mass related metrics in literature examples at least in the quality of the environmental factor
Keyword Literature
Reduction (Blaser et al., 2003),
Barbier addition (Lombardo et al., 2004)
Oxidation (Lenoir, 2006)
Pyrazole derivatives (Corradi et al., 2007)
Wittig–Horner vs. Claisen thionating reagents (Kuzemko et al., 2007)
Elliott's alcohol (Rosini et al., 2008)
Bromination (Eissen and Lenoir, 2008, Podgoršek et al., 2009a)
Methylation (Selva and Perosa, 2008)
Cross-metathesis (Rybak and Meier, 2008, Ho et al., 2009)
Photochemistry (Protti et al., 2007, Protti et al., 2009a, Protti et al., 2009b, Ravelli et al., 2010, Ravelli et al., 2011)
Asymmetric syntheses (Weiß et al., 2010, Eissen et al., 2010, Eissen et al., 2011a)
Biocatalysis (Gaber et al., 2010)
One-pot multi-step reactions (condensation–dehydration–reduction) (Climent et al., 2010)
Therapeutic proteins (Ho et al., 2010)
Methyl β-hydroxy esters (Fringuelli et al., 2010)
Phenolysis of epoxides (Zvagulis et al., 2010)
Hydrazides (Saha et al., 2010)
Microwave application (Villa et al., 2011)
Biolubricants (Akerman et al., 2011)
Aconitate esters (Piang-Siong et al., 2012)
Reduction of alcohols (Dobmeier et al., 2012)
Several examples (Andraos, 2006, Eissen et al., 2008)

Besides environmental issues, material flow management (not only for the chemical but also for textile, automobil, etc., sectors) has to be concerned with social and economic aspects too (see, e.g., Enquete Kommission “Schutz des Menschen und der Umwelt” des Deutschen Bundestages, 1994).

Therefore, the objective of the material discussed in this article is to create a learning situation in which a student is prompted to weigh up these three dimensions for a concrete synthetic example (bromination reactions). Thus, she or he will have to understand, recognise and interpret the interconnections of the different dimensions in dialogue within a cooperative learning scenario (see Wheeler, 2000 cited according to Burmeister et al., 2012) – this training can be understood as an education for sustainability rather than about sustainability (McKeown, 2006). As a prerequisite, raw material demand and waste production will have to be quantified and related calculations have to be understood. Metrics should become a natural part in synthesis design in order to back up claims of synthetic efficiency in research (Andraos, 2009) as well as in education. This article will provide the reader teaching material that can be employed in upper secondary and higher education and will report about its application in initial educational experiences. See Table 2 for a range of examples in chemical research.

Mass efficiency and life cycle assessment for sustainability

According to the Brundtland Report (United Nations, 1987) sustainable development means: “Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs.”

As the development and safeguarding of wealth in a sustainable manner is conceivable only in the framework of social harmony, only in accordance with a sound environment and on the basis of stable resource availability, are the three dimensions of environment, economy and social affairs equally involved. Chemistry, as one of the most important branches, can contribute to a sustainable development, because it represents a starting point for important mass flows (Eissen et al., 2002, Böschen et al., 2003, Eissen et al., 2004a). The “Conservation and management of resources for development” is one of the main foci of interest in Agenda 21 (United Nations, 1992). The utilization of resources must not exceed the regeneration rate just as little as the emission of substances should exceed the degradation/processing rate within the environment.

However, this goal can only be measured and controlled in a few areas of life. Therefore, a pragmatic approach is to choose the least harmful path. Comparing several products, one should prefer the option which

- has low costs e.g. for facilities, raw material extraction, product use → economy
- is more social e.g. by fewer accidents, more jobs, no children's work → social affairs
- protects the environment e.g. by less waste, emissions, raw materials, land use, by advantageous product properties → environment

Balancing and evaluating potentially opposing results is time consuming and in most cases practically impossible in class, especially against the background of the “green chemistry paradox” of using hazardous chemistry to develop improved production-scale processes (Ritter, 2010). A life cycle assessment (LCA), which highlights only one dimension of the three aspects, will hardly be conducted in industry due to the effort and costs. There are some essential approaches in large enterprises such as the eco-efficiency analysis (Saling et al., 2005, Saling, 2008) at BASF and the fast life cycle assessment of synthetic chemistry (FLASC) at GSK (Curzons et al., 2007). However, they are too complex and time consuming to be applied in secondary or undergraduate chemistry teaching.

Anyhow, in order to gain an initial overview, a simple mass balance can help, i.e., an illustration of how much raw material or waste can be recorded per product unit. Two alternative syntheses in the production of (R)-2-hydroxy-4-phenylbutyric acid (ethylester) (Scheme 1) will serve as an example. The mass balance of the reaction (Fig. 1) shows a relatively high auxiliary material demand and a high amount of sewage (in kilogram per kilogram product) for variant A, while it reveals that variant B is overall more advantageous. Remarkably, a complete life cycle assessment (Fig. 2) according to the method of EcoIndicator 95 shows the same result. As can be seen here, extraction (M4) and the subsequent recycling (M8) most adversely affects the sum of eco points: at the end the stepped line shows more points (Eco 95) for variant A than for variant B. There is also another case study showing that an LCA result is also obtained by a simpler approach (Ravelli et al., 2010). Another LCA examination (Jimenez-Gonzalez et al., 2011) provides support by the estimate that mass related metrics such as the process mass intensity (PMI), which, due to E-factor = PMI–1, is a kind of ‘brother’ of the E-factor, seems to be very reliable.


Two possible syntheses (variants A and B) of (R)-2-hydroxy-4-phenylbutyric acid (ethylester); a substance which is used in the production of pharmaceuticals (Blaser et al., 2003).
Scheme 1 Two possible syntheses (variants A and B) of (R)-2-hydroxy-4-phenylbutyric acid (ethylester); a substance which is used in the production of pharmaceuticals (Blaser et al., 2003).

waste (kg) of both variants per kg product.
Fig. 1 waste (kg) of both variants per kg product.

Eco-points for both variants of Scheme 1. M1 = catalyst; M2 = reduction; M3 = catalyst removal; M4 = extraction; M5 = solvent drain off; M6 = rectification; M7 = purification; M8 = solvent recycling. Reprinted from Jödicke et al., 1999, with permission from Elsevier.
Fig. 2 Eco-points for both variants of Scheme 1. M1 = catalyst; M2 = reduction; M3 = catalyst removal; M4 = extraction; M5 = solvent drain off; M6 = rectification; M7 = purification; M8 = solvent recycling. Reprinted from Jödicke et al., 1999, with permission from Elsevier.

Teaching approach

Background of the lessons

The above discussed aspects have been worked out into a lesson plan based on different worksheets given in the online resource. The lesson plans were structured for advanced upper secondary or undergraduate chemistry education.

For conducting the lesson successfully, students need a basic knowledge in both practical and theoretical organic chemistry. Students should be familiar with basic lab operations such as distillation, extraction, washing and drying as well as with functional groups, such as double bonds and esters, and basic organic reactions such as hydrogenation and bromination. However, in principle these basic lab operations, as well as the test tube reaction of an aqueous solution of bromine with cyclohexene (in juxtaposition to the non-reaction with cyclohexane), can also be explained during the course. In case the curriculum envisages oxidation numbers as another topic, related material (Eissen et al., 2011b) could be considered beforehand.

The goal of the teaching material is to explain how mass related metrics (Commitee on Industrial Environmental Performance Metrics et al., 1999, Curzons et al., 2001, Constable et al., 2002, Andraos, 2005, Augé, 2008, Calvo-Flores, 2009, Augé and Scherrmann, 2012), such as the mass index (MI, PMI or S−1; Constable et al., 2002)

ugraphic, filename = c2rp90002e-t1.gif
and the environmental factor (E; Sheldon, 1994)
ugraphic, filename = c2rp90002e-t2.gif
can both be used in order to evaluate the environmental performance of alternative synthetic pathways on an introductory level.

Aside from the overall number it is more important which category (e.g., solvents, auxiliary materials, coupled product, etc.) and especially which substance(s) contribute most to waste production in order to detect the optimization potential to save raw materials and prevent waste production. The combination of mass index (1) with substance prices delivers the costs in, e.g., Dollar or Euro per kg product. At least raw material costs can thereby be considered as one aspect of the economic dimension. One can consider health and safety aspects as part of the social dimension of a production process, namely the physical integrity of employees and population. Instead of utilizing metrics as, e.g., suggested by Eissen and Metzger (2002b), however, the qualitative discussion of, e.g., toxicity and combustibility is initially considered sufficient within the material offered.

The specific exemplary juxtaposition of mass balance and life cycle assessment shows the existence of different assessment qualities on one hand and, on the other, that a simple mass balance can, of course with due care, already deliver a sensible statement in the early phase of synthesis design. This is in line, e.g., with the German Federal Environmental Agency (Umweltbundesamt, 2009) which demands integrating an economical utilization of energy and material resources in the planning of syntheses. Regarding education, the agency points to the materials made available online by the internet organic chemistry lab course (Bahadir et al., Ranke et al., 2008). Insofar, the opportunity for a student to collect basic and partially crucial information about alternative syntheses should motivate an independent grapple with a case study.

Considering a familiar reaction (bromination of alkenes), alternative variants can be examined and discussed (Scheme 2). Surely, the information will not make a final decision possible. However, in this case the journey is the reward: qualitative differences, e.g., regarding toxicology or waste production, support the students' assessment competence, sensitize them for different environmental categories and provide insight into the activities of a chemist in the laboratory, who has to consider all these aspects and discusses them with chemical engineers. A corresponding series of worksheets is available for this purpose (Table 3). An information sheet precedes them, presenting the context which has been mentioned in the preceding passage and which relativizes the validity of mass balances versus life cycle assessments to a certain extent by means of a further case study (Eissen et al., 2008).


Bromination of alkenes by means of (1) bromine (Snyder and Brooks, 1943), (2) sodium bromide and perborate (Kabalka et al., 1998) and (3) hydrogen bromide and hydrogen peroxide (Barhate et al., 1999).
Scheme 2 Bromination of alkenes by means of (1) bromine (Snyder and Brooks, 1943), (2) sodium bromide and perborate (Kabalka et al., 1998) and (3) hydrogen bromide and hydrogen peroxide (Barhate et al., 1999).

The variants presented in Scheme 2 only represent a selection from many (Eissen and Lenoir, 2008). Further synthetic alternatives reverting to oxygen as oxidant can be found in the literature (Podgoršek et al., 2009a, Podgoršek et al., 2009b). The worksheets (Table 3) deal with metrics such as yield, mass index, environmental factor E (for variant 1 see eqn (1), Fig. 3) and cost index (Fig. 4).

 
ugraphic, filename = c2rp90002e-t3.gif(1)
Furthermore, qualitative aspects such as toxicology and safety are thematized. Simultaneous consideration of the different aspects is demanding and delivers interesting discussions which can train communication and judgement competencies. The course proceeds in small steps so that students can track the determination of metrics in order to prevent supporting software being used as a black box. The software (EATOS) (Eissen and Metzger, 2002b, Eissen and Metzger, 2002a), referred to in the worksheets, was developed specifically for the design and assessment of syntheses in the early phases of development. Students should realize that the software is a helpful instrument and employ it in a goal-oriented manner.


Environmental factor E for three syntheses of Scheme 2. A zoomed presentation can be found on the right hand side, in order to better identify coupled and by-products.
Fig. 3 Environmental factor E for three syntheses of Scheme 2. A zoomed presentation can be found on the right hand side, in order to better identify coupled and by-products.

Raw material costs (see worksheet Table 3) for the production of dibromocyclohexane (Scheme 2). Water, which is presented in protocol 3, belongs to the solutions of hydrogen bromide and hydrogen peroxide.
Fig. 4 Raw material costs (see worksheet Table 3) for the production of dibromocyclohexane (Scheme 2). Water, which is presented in protocol 3, belongs to the solutions of hydrogen bromide and hydrogen peroxide.
Table 3 Content and problems of the worksheets, which are used in the course. See the ESI for details
Work sheet/Content Problem/Content Cognitive skills
1 Three synthesis protocols of a bromination 1 Oxidation reaction from bromide ions to bromine Knowledge/Remembering (of oxidation state and electron donor and acceptor relations)
2 Yield of a reaction Knowledge/Remembering (of the product – key-substrate ratio)
3 Criteria for the selection of a synthesis protocol Comprehension/Understanding (of the information sheet)
2 Concretisation of the three dimensions of sustainability with corresponding topics:

 1. Resource efficiency

 2. Production of waste materials

 3. Raw material costs

 … (continued on worksheet 3)

 4 Ratio of substrate and product amount (→ Topic 1) Application/Applying (of the mass index S−1)
5 Amount of by-products and substrate excess (→ Topic 2) Application/Applying (of stoichiometric substrate consumption and of the yield (see Problem 2))
6 Ratio of waste and product amount (→ Topic 2) Application/Applying (of environmental factor E)
7 Raw materials and waste of three protocols (→ Topics 1 and 2) Evaluation/Evaluating (of substance amounts regarding synthetic efficiency)
8 Software support being available for Problems 4 to 6 in order to receive relevant data (Problems 7 and 9). Application/Applying (of a new software tool)
9 Substance costs (→ Topic 3) Simple multiplication procedure
3 … 10 Environmental, health, safety and costs as parameters relevant for the assessment of the sustainability (→ all topics) Evaluation/Evaluating (of substance amounts and cost as well as qualitative criteria (e.g., toxicity, flammability) regarding synthetic efficiency)
4. Hazards of applied substances
R-phrases of considered chemical substances

In principle, these calculations are not a prerequisite, since the results are indicated on the worksheets. Finally, the interpretations of results should remain at the centre of the worksheets and to a lesser extent the way in which they were obtained. Such examinations are so fundamental that they can be/are applied within research at universities, and in industry (see Box 1 in the literature (Eissen et al., 2008, Eissen et al., 2010)).

Course of the lessons

Introduction into criteria concerning sustainable chemistry. In the beginning of the lesson plan the students are acquainted stepwise with industry-typical evaluation criteria in early synthesis design, such as environment, health, and safety (EHS). Life cycle assessment and simple mass balances are juxtaposed. In the worksheets (Table 3) the students begin with simple chemical specific aspects such as a relevant oxidation reaction and how to determine the yield of a reaction (Table 3, Problems 1 and 2). In order to achieve motivation related to EHS criteria, the students are prompted at first to collect relevant criteria for the synthesis design themselves (Table 3, Problem 3).
Metrics and their calculation. The problems (4 to 6, Table 3) offer an instruction for the examination of three synthesis variants (Scheme 2) by the determination of metrics such as yield and environmental factor (Fig. 3), which McKenzie et al. (McKenzie et al., 2005) put into the centre of the comparison of chemical syntheses, too. In this way, the stoichiometric calculation concept can be conveyed to the students. Thus, a corresponding software tool is not considered a black box and its application is rated to be trustworthy. However, in case this aim is not considered to be important, the problem(s) could be omitted.

The comparison of the three variants represents the actual goal, which is linked with the preparation of a mass balance (Table 3, Problem 7). The raw material and waste amounts have to be interpreted sensibly. Here, as in reality, the varying data quality plays a role: for two variants the quantitative information regarding the work up is missing. It has to be pointed out that the result of a mass balance is already given. This is provided on the basis that a discussion of the synthesis variants is available and does not have to be created only by (software assisted) calculation. The environmental factor and the mass intensity can be viewed in a more differentiated fashion than simply juxtaposing the metrics. The sample solution to Problem 7 highlights the waste treatment – a perspective which is rather unfamiliar to young students. Therefore, the worksheet promotes an early sensitization for the isolation part of a synthesis and, in this regard, is considered to be an important contribution to a chemists' education.

After all, the calculation is only a means to an end. The same is valid for Problem 9 (Table 3), in which the costs per kilogram raw material and the used substance amounts are already given in order to compile a cost index (Fig. 4). Determination of substance amounts can be tracked by applying the software EATOS (Table 3; Problem 8). List prices, which are usually not noted in Euro/kg but, for example, in Euro per 2.5 L (see sample solution), can be recorded in EATOS, which converts automatically to Euro/kg. However, the tasks are designed in a way that a comparison of the given synthetic protocols is possible, so that Problem 8 (application of EATOS) could simply be ignored.

Hazards of applied substances. Finally, costs and qualitative aspects such as toxicology and flammability have to be included in the evaluation. For example, hydrogen peroxide is a dangerous substance and can be used to experimentally illustrate hazards in chemical production plants by runaway reactions (Eissen et al., 2003b). An overall consideration is required in Problem 10 (Table 3). The sample solution should be understood exemplarily. Since one cannot expect the students to come up with all arguments and considerations, it is advisable to make available the sample solution after discussion.

Experiences and evaluation

The described teaching was tested in advanced upper secondary chemistry education. Three learning groups of about 8 to 15 students respectively worked with the lesson material (total number N = 35).

The information sheet was read and discussed within half an hour. The time demand was about 40–50 min for worksheet 1 (Problem 1–3), 60 min for worksheet 2 (Problem, 4–9, Problem 8 was left out) and 45 min for worksheet 3 (Problem 10) (Table 2). In one learning group the above mentioned basic knowledge on the conversion of cyclohexene and cyclohexane with an aqueous bromine solution was communicated prior to working with the worksheets. The final Problem 10 could be understood as an extention of Problem 7. The latter only required 15 min in most cases. The students quickly identified the first pathway to be the most resource efficient procedure. The question as to what extent inherently safe substances can be weighed up with technological solutions for problematic substances is an interesting subject for a discussion (compare “green chemistry paradox” (Ritter, 2010)). That is, Problems 7 and 10 prompted the students to weigh up different aspects and to evaluate them, what is the highest level of requirement among the problems listed in Table 3. In two classes, most aspects were mentioned in a written statement. Interestingly, the economic performance (see Fig. 4 and solution to Problem 9) and toxicology of substances seemed to have a crucial impact on the students' opinion. More than half of the students considered pathway 2 of Scheme 2 to be preferable. Thus, the instructor should pay intention that waste disposal costs (e.g., for sodium borate) and potential solvent recycling are included in the discussion as well as substrate costs which might become more relevant for more expensive alkenes. In another class, unnamed aspects were integrated into the discussion by providing the sample solution. This was considered helpful to expand the students' perspective.

There seemed to be a need for a certain prearrangement. Necessary information has to be gathered (Problems 4, 6 and 9) by application of distinctive procedures using corresponding metrics. According to the students who where asked for their opinion, Problem 4 to 6 (Table 3) contributed to an understanding of the calculation procedures. The time demand to use EATOS to reproduce the data shown in the worksheet – Table 1 and 2 was about 40 min (worksheet 2). In the students' opinion the software greatly facilitated the amount of work and they appreciated the indication of results in the worksheet for the purpose of control.

Going further back to the logic of the problem composition, Problems 2, 3 and 5 were considered appropriate to prepare and support the cognitive capability for Problems 4, 6 and 9. They delivered the knowledge of calculation procedures making transparent the generation of relevant data, e.g., concerning waste production. However, some students had problems in successfully calculating the by-product amount (Table 3, Problem 5). The discussion with the instructor was necessary to make clear how to understand the theoretical mass flow within a stoichiometric reaction equation.

After the lesson plan, a Likert-questionnaire (5-step) was administered to the students in two of the learning groups (N = 22). The questionnaire comprised of 15 questions on the students self-reflection of the learning process, their perception of the changed focus of the lesson plan, and the consideration of the teaching materials. Feedback was collected from 22 students.

Overall, the students gave very positive feedback. The questions on the sustainability criteria and assessment competencies concerning mass balances and economic, ecological and social aspects were answered most affirmatively. The students were felt to have got an understanding of assessing criteria in the green chemistry context. They expressed their feeling to be able to assess chemical processes in the foreground of sustainability issues. The triple result of 73% and 27% is coincidental, the composition of students in the different groups of answers is different for these questions. The same is true for the questions related to the mass index and environmental factor (Table 4). The students agreed to have predominantly received a different view on chemistry and that they got an insight into chemistry's efforts to support sustainability. The wider focus of the lessons based on these teaching materials was widely acknowledged and helped the students in understanding how chemical processes are assessed (Table 5). Also feedback on the teaching material was very positive. The teaching materials seem to be feasible and interesting to the students (Table 6).

Table 4 Questionnaire regarding the felt learning success
  agree rather agree undecided rather do not agree do not agree
I can state criteria for the assessment of sustainability of chemical syntheses.
  73% 27% 0% 0% 0%
I can assess synthetic protocols regarding resource demand and waste production.
  73% 27% 0% 0% 0%
I understood what the mass index is.
  50% 32% 18% 0% 0%
I understood what the E-factor is.
  50% 36% 9% 0% 5%
I have learned to assess synthesis procedures regarding economy, ecology and social aspects.
  73% 27% 0% 0% 0%

Table 5 Questions regarding perception of the course
  agree rather agree undecided rather do not agree do not agree
The teaching unit equipped me with a different view of chemistry.
  32% 45% 9% 14% 0%
The teaching unit delivered insight into the efforts of chemistry for sustainability.
  41% 41% 18% 0% 0%
It is important that impacts of chemistry on environment, economy and society will be reflected in education
  55% 36% 5% 5% 0%
I would have preferred to only devote myself to synthetic procedures and formulas.
  0% 5% 18% 36% 41%
The teaching unit vitalized my capabilities to better assess chemical processes.
  36% 50% 14% 0% 0%

Table 6 Questions regarding considering the teaching materials
  agree rather agree undecided rather do not agree do not agree
a This question was only answered by those thirteen persons who only recently worked with the computer tool.
The information was understandable and reasonable.
  41% 41% 18% 0% 0%
I liked the application of the computer software.a
  54% 23% 23% 0% 0%
The tasks were too difficult.
  0% 0% 36% 41% 23%
I was able to cope well with the teaching material.
  19% 62% 19% 0% 0%
The problems were interesting and challenging.
  9% 59% 23% 9% 0%

Conclusions and implications

The focus of this article is learning about evaluating efficient resource utilization and production in chemical synthesis and provides training opportunities (Hansmann et al., 2010) also for communication skills. Along with the developed tasks and worksheets, students dealt with aspects of safety, health and environment, using three bromination reactions as an example. Mass balances, raw material costs and qualitative properties (toxicology, flammability, etc.) were considered against the background of the concept sustainable chemistry. By these means, the material described in this article was designed to contribute to new curricula which are desired for a green chemistry culture (Tucker, 2010), and is considered to be appropriate by the students.

From the experiences, the lesson plan proved to be feasible and motivating for students on upper secondary level. Its design and demands should also be suitable for students on undergraduate level, when it comes to integrating a quantitative approach into green chemistry efforts. For a quantitative look also at qualitative characteristics such as toxicology, see, e.g., Eissen and Metzger (2002b), Saling et al. (2005), Martins et al. (2007), or Saling (2008).

Of course, there are also alternative areas which are part of the concept of sustainable chemistry and are worthwhile to consider. Emissions could be a further subject, e.g., their distribution and spreading in the environment or strategies for their avoidance. The latter is, amongst others, the subject in the consideration of musk fragrances (Marks and Eilks, 2010) and pharmaceuticals (Eissen and Backhaus, 2011) in the environment. The herein described lesson plan can be expanded to these areas and the gained knowledge and competencies might be transferred to other areas for building up a more settled understanding of chemistry's contribution to sustainable development.

Notes and references

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Footnotes

† This article is part of a themed issue on sustainable development and green chemistry in chemistry education.
‡ Electronic supplementary information (ESI) available: Worksheet. See DOI: 10.1039/c2rp90002e
This journal is © The Royal Society of Chemistry 2012