Transcription
Let's start, guys. This is the first, the first slide that appears at Ca' Foscari. So, if any of you need help to pass the exam, to get the notes, for any kind of certified disability, contact me directly at the disability service. We are here at your disposal. Obviously, this is not a laboratory course, so some problems related to the laboratory obviously do not exist. Okay? The course is called Green Chemistry. It should be somewhat representative of our degree program in Chemistry and Sustainable Technologies. What is that green you see on the slide? What does it look like? A forest? Instead, they are molds. Today, someone told me that I teach a Green Chemistry course, so it means everything is covered in mold. I hope to show you that it's quite the opposite, in other words, that it's a science, or rather a mixture of sciences, quite diversified and a bit more exciting than something moldy. Take it with a grain of salt. So, this is the only slide with a bit of Italian. Perhaps a few others. All the slides in the course are in English. I will speak in Italian, but I expect you to be able to read them, okay? We will read what is written together when necessary, and you will soon realize that this is not a hard science course, as they say. That is, it will not be a course like Organic Chemistry, Organic Chemistry 2, like Physical Chemistry, like Physics, like Mathematics, where you are taught mathematical methods, chemical methods, a language. This is a course a bit more about the logic behind the development of chemistry and how chemistry is developing today. So, it covers all disciplines of chemistry, mainly organic chemistry. I am an organic chemist, and I have become a chemist who does green chemistry, sustainable chemistry, benign chemistry, call it what you want, because it is easy for an organic chemist to develop clean processes and use clean reagents, change types of solvents, etc., etc., to move towards more sustainable chemical production. However, I mean, it is not limited to a single discipline of chemistry; it covers all of them, as I said at the beginning. Okay? It is definitely a multidisciplinary science, and I will show you this as we go along. We have fifteen lessons, okay? I expect a minimum of involvement from your side. That is, don't make me talk for an hour and a half, because I can't do it, and you can't do it. I can't talk, and you can't listen to me. So, if I ask you simple questions, I try to involve you. Meet me halfway, let's help each other. I learn more, you pay more attention, you get bored less, I have less difficulty. The advantage is for everyone. Let's start with a couple of slides today. The first lesson is introductory, but not too introductory, in the sense that we will also tackle fun things, some of the great disasters of chemistry, okay? That we are proud to tell our friends or acquaintances, and that represent, a bit, the tip of the iceberg of what chemistry is, the perception of chemistry at the level of society, of the population, of people not trained and not educated to be chemists. My goal is not to impress you or show you fun things, because they are not particularly fun, but they are interesting, and to lay the first brick in what should be the fundamental idea of a chemist, which is to be aware of the possible dangers, risks, toxicity, and hazards that chemistry has, and to try to overcome them. So, the goal of green chemistry is to overcome chemistry done without thinking, without being... it was not a discipline, it was a productive discipline, no? Chemistry, industry produced, regardless of the consequences for the environment, for human health. Now things are changing a bit, fortunately, thanks to green chemistry. A couple of quotes at the beginning. I see and read in English, then I will translate them. "The scientific and technical know-how to understand and address problems related to chemistry." I wanted to say that a trained chemist, a chemist who has studied chemistry, has the scientific and technical knowledge to understand, address, and solve and prevent problems related to chemistry. Where the keyword is "prevent," okay? You will hear it repeated many times. We talk about prevention. This is why this teaching of green chemistry is important. "Because your chemical knowledge coupled with the knowledge of potential dangers, and we start from here today, of potential solutions available, and we will talk about these extensively throughout the course, will contribute to developing a chemistry that is safer, more efficient, more profitable, and better accepted." So, you see here, in this course, there is not only science, and there will be a lot of it, because I will give you a lot of examples of chemistry, because we are all chemists. But there is an emphasis on what must be economically sustainable, okay? Not economically advantageous, but economically sustainable, because no one will ever produce something if there is no return. No company does business at zero cost. And "better accepted" means that society must be able to accept it, understand it, and make it its own, without thinking that it is necessarily negative, given the epithet "chemistry." In English, they talk about "chemistry." The word with the "c" at the beginning, "chemistry," no? We, from our department, have removed the word "chemistry." It is called the Department of Molecular Sciences and Nanosystems, because there is a prejudice towards the word "chemistry." In reality, we have not removed it from the name of the department for this reason. In reality, we are beyond that. The idea was to give the department a connotation that does diversified things, not just chemistry. But if you go out and talk about being a chemist, they say, "You go to the lab, you do smelly things, you do dangerous things, you do polluting things." It's true. They used to tell me that. The story that a colleague told me, which I always tell, perhaps I've already told it to you, no? But perhaps not. It's that when I went to a big party, they asked, "What do you do?" "I'm a director." "I'm an actor." "I'm a designer." "I'm an architect." "What do you do?" "I'm a chemist." Okay. But then I thought about it. The next time, "What do you do?" "I'm an architect." "I'm a designer." "I'm a fashion designer." "What do you do?" "I'm a molecular designer." Ah, what a nice job. And it's obviously the same thing, no? So, think of yourselves as molecular designers if you want to make yourselves a bit better, a bit better from the outside. It's a joke, but I mean, the logic is a bit like this. Another quote, David Attenborough: "Self-control in governing ourselves, the benefit of the population, based on our actions to ensure the survival of the environment." Instead of controlling the environment for our benefit, perhaps we should start controlling our actions to ensure survival. So, the first line above is the past, the second line below is the present, the future. That is, until 20 years ago, the idea was to exploit the environment to derive a benefit, both from the point of view of production, well-being, life, etc., etc. Now we are realizing that it is not possible, that the environment must be protected for future generations, obviously. And so, we are proactively controlling our actions, what we do, to ensure that the environment remains unchanged. This is what we mean by sustainability, okay? If there are questions, comments, criticisms, stop me at any time, okay? If you don't understand what is written on the slide, ask me, stop me. We are here, there is plenty of time, there is no problem. This is a slide that I use to show the infinite ramifications of green chemistry and to teach you something, something quick. How many of you have taken the bibliographic research course in the library? Still very few of you. You have been asked, indeed, strongly advised, not yet mandatory, to follow a bibliographic research course before entering an internship, no? That is done in the library. Are you aware of it at least? Because I tell you, because below there is a writing. Who can tell me what it means? What is this? This is a bibliographic reference, okay? To a journal called Green Chemistry. Well done. Imaginative. What is this? This is the volume. Every year, more volumes are released, and they are numbered in progression. These are simply the page numbers. When I cite something that does not belong to me, that is not mine, I try to always put a bibliographic reference, whether it's a book, an article, even a website where possible, because I want to put you in a position to retrieve all the material that I present. So, I give you the reference and you can go and look at it where possible. I know you won't do it in most cases, but sometimes something interests you, and you will go and search for it. The second reason why I show you this is that Green Chemistry calls the author, because it represents the sum of everything that Green Chemistry deals with. Chemistry written like this, like the tree of chemistry. And we will talk about it extensively because it will be the structure of our course. But you see, there are 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 main branches, each labeled in a different way: Inherently Benign Chemistry, Less Hazardous Synthesis, Catalysis, Use of Renewable Feedstocks, Real-time Analysis for Pollution Prevention, Waste Prevention, Design for Energy Efficiency, Design of Chemicals, Design for Degradation, and finally, Reduce and Reuse. And as we go on, you will understand the meaning of all these twelve, of these twelve phrases, because they are the twelve principles of green chemistry, which we will touch upon today, and which will be the guiding thread of this course. And the leaves are all a series of possible technologies used to implement each of these ramifications, these principles. They are not so disconnected. Each of these technologies that can be used is intimately connected with others. For example, in catalysis, which many of you have been exposed to, there is enzymatic, bio-catalysis, organo-catalysis, catalysis with abundant metals, okay? Nano-catalysis, heterogeneous catalysis, for example. So, there are all branches of catalysis that can contribute to improving the environmental or green performance of a given chemical reaction. This article, by the way, was published recently. You see, we try to stay updated. That is, don't go and read stuff that is too old. It's a bit of a summary of the last twenty years of green chemistry. Green chemistry, 20 years, 25 years. When I started my postdoctoral career, people started talking about it in the mid-nineties, okay? And Green Chemistry was a term coined around the mid-nineties by a person I will show you later. So, it's a recent discipline. It's branching out, but it's reaching a lot of sectors where initially one couldn't even imagine ending up. From the thematic things, for example, let's see what else is there. Life Cycle Analysis is in here, okay? The life cycle analysis of compounds. So, it's becoming increasingly branched. I encourage you to read the literature. I will pass around the article from which that photo is taken, not to scare you, because I don't want you to read it, it's 40 quite dense pages, but it gives you a sense of what's there. Download it from the Ca' Foscari website because it's available, we have the subscription, so you can download it legitimately and save it and look at it for inspiration. I give it to you because that article is structured like this course. That is, we take the twelve principles and gradually delve into each of them, explaining some aspect that is important, crucial, significant for green chemistry. It's not a comprehensive course. It's a course that should make you curious to try to improve environmental performance for the health of whatever you will do as chemists as you go forward. Questions about this tree of chemistry? You will see it, you will understand it often, okay? The objective today is to understand the historical perspective of the preceding years before the birth of green chemistry, which led to the birth of the word and therefore the typical way of operating of green chemistry, and to understand the development and growth of problems and critical issues that have emerged from industry and from the production or dissemination of the use of various chemical products, okay? The why of green chemistry, where does this necessity, this discipline, come from, when, how, where, why? So, some definitions, but they are not real definitions, mind you. You can find them on Google, download them, no need to write frantically. Listen to me. If you lose the thread, stop me, etc., etc. Green Chemistry, Benign Chemistry, Clean Chemistry, Sustainable Chemistry. We will get to that later. It's not exactly the same thing. It refers to the synthesis, processing, use, and also the end of the life cycle, I add, of chemical products. The goal is to reduce the risk to humans, to the human population, and the impact on the environment, okay? So, health, environment, and safety are the three words at the base of green chemistry: health, environment, and safety. What was said at the beginning: chemistry has an intrinsic dichotomy. There are positive aspects, negative aspects. I ask you, some positive aspects of chemistry? For you, it's easy because you studied chemistry for some reason. What has chemistry contributed to improving in the last 100 years? Tell me, because I won't show you the cards later. Even what is written, but if you propose some ideas, it's all to the good. What's positive? New drugs. I mean, life expectancy is now 85 years. In 1900, it was half. I would already be dead. Hey, you wouldn't be, but I would. So, pharmaceutical chemistry and the impact on health have been enormous. Chemistry, then, what else? Don't be shy. I don't want shyness in here. Pretend you're in Organic Chemistry 2 lab, where you used to bother me every three seconds asking for something. Understanding of matter, so the beauty of understanding how atoms and molecules behave, how they assemble, etc. So, knowledge. And this is an aspect I hadn't included. Message, I mean, okay? Just understanding matter. More down-to-earth. Polymers, plastics, which are polymers. Your mobile phones. How much chemistry is in our mobile phones? How much chemistry do they have inside? Okay? There are materials, there is electronics, there is the screen, which has something for some reason that has nothing to do with anything other than chemistry and physics. The batteries have a series of chemical compounds inside. The number of chemical compounds, of chemical elements, excuse me, not compounds, in a phone, I believe, approaches 80. Out of 90, maybe not 80, but 50 for sure. So, all consumer goods. And in nutrition, preservatives, even in refrigerators, I mean, they are a form of preservation that is based on chemistry to some extent, on the development of some compressible, expandable gas that makes refrigerators work. The brake frames. We will also talk briefly about frames later, because they are not exactly environmentally compatible. It will indeed be one of the examples I give you of where chemistry has evolved, from chlorofluorocarbons to something more sustainable. What else? Fertilizers. Fertilizers. Now there is more food for everyone, because we are becoming 8 billion people on the planet. We also have to think about this. And so on. So, moving forward, there is the medical revolution, what he said, food production and preservation, preservation of food. We haven't mentioned fuels, transport, okay? What's in Marghera? There's an oil refinery that transforms oil into fuels, diesel, gasoline, etc., etc., etc. So, yes, another example of green chemistry. But when we went from leaded gasoline to unleaded gasoline, you don't even remember it because you weren't even born yet, maybe. Yes, because it says "unleaded" on the gasoline. What's the point of adding lead? We will also see why it made sense to add lead, rather than not. Materials for transport and communication, clothing, sports, etc., etc. Dyes, fabrics, okay? They can be considered frivolous consumer goods, but they are not, because each of us wants the best sweater in the right color, the phone that works, the car that works, so a healthier, longer, and more pleasant life. Negative aspects of chemistry. More pollution is one, obviously. Some girls in the back, only boys are listening. Girls, be brave. Negative aspects of chemistry. Waste. The need to dispose of, treat, convert in some way, manage the production of waste. Let's see what comes out. Health, okay? When we talk about health, about dangers from exposure to chemical products of any type and kind, we are talking about health. Environmental problems. We will see some quite significant ones as we go along. Today, with the lesson, unsustainable use of resources. Unsustainable use of resources. Does anyone know an example of unsustainable use of resources? Petroleum, for example. Easy example, okay? We use resources that could eventually run out, or at least increase the level of CO2 in the atmosphere and lead to irreversible warming of the planet. What is the connection between the use of petroleum resources and the increase of CO2 in the atmosphere? Could you explain it to your brother who studies philosophy? Exactly. And then this CO2. You said it correctly. Burning petroleum, one of the products is CO2. And then this CO2 remains in the environment for a more or less indefinite time. Conversely, if you burn wood in the stove, in principle, you burn wood, you produce CO2, but this CO2 could be re-fixed by a plant to produce wood again and close the cycle, which would be the most desirable thing. So, CO2 increases in the atmosphere because we are burning an irreversible resource. That is, fossil resources that take 10 million years to become fossil resources. So, clearly, that cannot work. So, toxicity, pollution, environmental damage, and resources that are running out. This is to say that chemistry has positive aspects, negative aspects. We keep all the positive aspects, and we cannot do without the positive aspects. That is, if there is an industry that produces something, it's because there are positive aspects. Now, we also need to consider the negative aspects and try to remedy them. And this is the goal we set for ourselves as chemists. Chemistry improves life, but it is equally true that chemical products can be dangerous and toxic to the environment. And I think we agree on this, we understand each other, no? Nothing transcendental. When does it all begin? It begins in the 60s. This lady, Rachel Carson, published this book, Silent Spring. It's in the library. If any of you are interested in understanding how the perception of the danger of uncontrolled and irresponsible use of chemical products arose, go and look at this book. It contains a full analysis of cases of DDT, environmental pollution, etc., etc. And it was a revolutionary book, okay? At the time, the perception was that these were marginal aspects, and large industries strenuously opposed the publication of this book precisely because it contained concepts and exposed problems that were real but were being hushed up. Have you seen the movie Erin Brockovich? With Julia Roberts? About chromium pollution of groundwater? That's also an example of what's in here. So, it was published in '62. One of the main chapters is about DDT. It caused a huge awakening of consciousness and caused the beginning of environmental regulation in the United States, which then gradually progressed. What is DDT? It's a pesticide. The structure is that. Okay? It's dichlorodiphenyltrichloroethane. This is DDT. Initially, it was used to disinfect from mosquitoes carrying malaria. It saved millions of lives. DDT, okay? It was used somewhat liberally, let's say, because it was considered very safe. What Rachel Carson showed in the book is that it enters the food chain and causes damage, mutations, death in organisms, and therefore an imbalance of the natural environmental cycle. So, what they realized is that the eggs of Canadian geese that grew, that were laid in areas heavily treated with DDT, had very fragile shells, and the birds disappeared from one year to the next. They disappeared, okay? Because with the fragile egg, the fragile shell, the young did not grow and died. And so, man, when things went wrong, a disappearance of wild birds was noted. So, they asked themselves why wild birds disappeared. They saw that the eggshells were terribly thin. Where does this thinning of the calcareous shell of the eggs come from? And they traced the chain backward: large fish, small fish, plankton, phytoplankton. DDT had entered the food chain because it is a lipophilic compound, okay? So, it accumulates in fatty tissues, okay? Phytoplankton contains triglycerides, lipids. Smaller and smaller fish, etc., etc., until the large fish had very high levels of DDT because it accumulated in the fattest tissue. The fish ate the fish, excuse me, they ate the fish and transferred to their eggs the DDT that caused this, that caused these problems. One of the most striking cases was in the 1950s in Borneo. There was a malaria epidemic. The World Health Organization authorized immediate action. That is, it said, "Before millions of people die, it is necessary to use DDT to eradicate mosquitoes." DDT eradicates mosquitoes, naturally, and prevents the proliferation and spread of malaria. It works, I repeat, it works very well. It saved millions of lives. So, later we will ask ourselves a question about this. But it didn't just kill mosquitoes; it also killed bees, for example. By killing bees, some caterpillars no longer have environmental competitors and predators. So, they spread and cause... they eat the roofs of houses. They found themselves without a roof over their heads, just to say the least. More seriously, it enters the food chain, causes neurological damage, and in the end, the most resistant species, which are rats, also proliferate compared to less resistant species. Less resistant species to DDT, and bacterial infections, epidemics, etc., etc. So, what was born to save, to protect the population, ultimately proved to be used irresponsibly as a problem bigger than perhaps what it helped to solve. A question one must ask: is DDT necessarily a bad chemical compound? Is it intrinsically bad? It's just a chemical product, okay? Made by humans for a specific purpose: to kill insects that transmit diseases. At the time, the idea was this: DDT is produced because it is needed to kill mosquitoes that spread malaria. Everything else that came after was not on the radar of those who produced DDT. So, this is the question we ask ourselves when we make a chemical product, develop a process, create something. We can no longer stop at this point and say, "We have solved the problem." We go further and see if we are creating others, or how to solve them eventually. The cumulative effects were poorly understood at first, and it proved too efficient at killing too many different species. So, in the end, DDT was banned in many areas. In many parts of Africa, it is still used because it is the only alternative to dying of malaria. The point is that if one has to develop a different insecticide that kills mosquitoes, it must maintain the function of DDT, which kills mosquitoes, and must address the problem of eliminating the side effects we have discussed so far. So, the goal is to understand the chemistry behind it, to understand the biology behind it, to understand the psychology behind it, etc., etc. So, the broader effort must be to synthesize a new drug, a new pesticide, that has the same effects as malaria without having the side effects we have discussed. Another case I will dwell on a bit less, but still very striking, is called Thalidomide. You have probably heard of it. It caused 10,000 babies to be born with deformities, to be precise, okay? And here we go a step further. Here, a chemist is needed to understand why. So, Thalidomide, you see it also has a chiral center, okay? This carbon is chiral. One of the two enantiomers functions, the other causes damage to the fetuses. So, here you understand that the study of chemistry goes beyond, okay? You just need to be a chemist to know what chirality means and therefore what interactions the R-enantiomer can have with certain enzymes compared to the S-enantiomer. So, your knowledge is required here when you become chemists and go out into the world. And indeed, the S-enantiomer is used to treat leprosy, and as a starting molecule for anti-inflammatory drugs. Nothing intrinsically bad. The use made of it is bad. Other cases: one, he mentioned it earlier, CFCs, chlorofluorocarbons, ozone hole. I will not talk to you about stratospheric chemistry, radical chemistry that causes the depletion of the stratospheric ozone layer. I don't remember which one protects us from UV radiation. What is there today instead of chlorofluorocarbons in our refrigerators? Your mother might ask you, "You, who are a chemist, explain to me how refrigerators are now considered more environmentally compatible and sustainable." Does anyone know? No one knows. I hate to ramble, ramble. No, no, no, no. So, there are HFCs. As long as there is a hydrogen in there, okay? Because these problems wouldn't even arise. But even simpler, because the chemistry of chlorine and fluorine is not particularly striking. There are light hydrocarbons. Go and look at the label of your refrigerator at home. Nine out of ten new refrigerators have butane as a refrigerant gas in them, okay? Flammable, mind you. These are not flammable. They are stable under normal conditions, except under ultraviolet radiation, etc., etc. Another example he accepted: tetraethyl lead. It was added to gasoline to prevent engines from knocking. It was an anti-knock agent. It served to prevent the mixture in the cylinder from exploding before the cylinder reached the end of its stroke. It was a perfect, economical anti-detonation inhibitor, a fantastic organometallic compound. The problem is that lead causes poisoning and accumulated in crops, for example, along the sides of roads. Then, by consuming food, it entered the circulation, and alternatives were developed. You see here, it's green chemistry ante litteram, mind you, because we are talking about before. Alternatives to chlorofluorocarbons were developed, and alternatives to organolead compounds that go into gasoline were developed. You see, ethanol, isobutane, ether, and so on. There are ways to intervene in these cases. Another few disasters that I will not dwell on. You can go and look them up. You see a beautiful river burning because it was full of hydrocarbons. These were major events in American history, in this case, from the 60s, 70s, 80s, that caused environmental legislation, first, social perception, the realization that one could not continue to operate so freely, and then consequently, the birth of all environmental legislation. It should be here soon. This is an example from our home, okay? You weren't born, I was. I remember it, I was little, but on the news, there was this event. And here we talk a bit about chemistry, because after all, you are chemists. Carda Seveso. Have you heard of it? Dioxins. Have you heard of them? This is the mother dioxin, tetrachlorodibenzo-p-dioxin, okay? The reaction that this company did was from tetrachlorobenzene, an hydrolysis to make trichlorophenate, okay? This is a phenate. Hydrolysis and then phenol. The reaction went a bit on its own, and due to carelessness, lack of knowledge, a series of unforeseeable fatalities, it resulted in the release into the environment of a quantity of dioxin that has contaminated the area to this day. They are still checking today, because I also talked about it here. I don't want to scare you or make you lose the desire to study chemistry, but only a chemist knows what is written on the board, right? So, only a chemist can predict the consequences and remedy them. So, the idea is that only a scientist can act to avoid the disastrous consequences that any human activity, in this case chemistry, can have. And here I show a couple of slides that you can go and read. There is an article published a few years later, you see, in '85, by a person in charge of the Lombardy region about Seveso, which explains a bit what happened. So, Saturday, July 10, 1976. Saturday, July 10, at 12:30. Does this tell us anything? No. So, the ICMESA process. ICMESA was the company. From tetrachlorobenzene, they produced trichlorophenol, which is this one below, okay? Alkaline hydrolysis of tetrachlorobenzene at atmospheric pressure, between 140 and 170 degrees, in a solvent, ethylene glycol. At the end of the hydrolysis, there are sodium trichlorophenate, trichlorophenate, glycol, and sodium chloride, of course, and water. There is some xylene that they used to distill away the water. This is too much for me. This is too much. This is too much. So, xylene and ethylene were removed by distillation, okay? At a certain point, after that, the remainder is diluted with water. It means it's acidified, it's protonated the phenate to give the phenol, and the desired product is obtained. The reaction started, went on, went on beyond what is interesting. That inside there were 2030 kg of sodium trichlorophenate, 2030 kg, 2 tons of stuff, 500 kg of sodium chloride, 1000 kg of glycol, actually a bit more of polyethylene glycol, okay? So, we are talking about truly industrial chemistry. You are chemists, or industrial chemists. All of you. There will be some industrial chemists. Shame, because this is industrial chemistry. But the chemistry you study is useful for understanding industrial chemistry. So, there's little to do. This is the reaction. These are the quantities involved. So, this is the timeline, the events in chronological order as they happened, taken from that article that you have. If you want to read it quickly, the reference is above. You can find the article online easily. So, July 10th, remember, it's a Saturday. So, the 9th, Friday morning. So, production begins on the 9th in the morning, actually Friday afternoon at 4 o'clock. Production begins, okay? It's heated and stirred all night until 5 in the morning. After that, heating and stirring are stopped, and they check if the mixture is at a temperature that was known to be 180 degrees. A parallel exothermic reaction, not the desired one, started. They check that the temperature is below 150-160 degrees. I think they checked it was 158. They all go home. Because it's Saturday. So, there's the fatality. They all go home, and at 12:37, the overpressure disc blows. No, all the reactors are closed, actually they vent because of the pressure. They cool it down and leave it there, saying, "We'll deal with it later." Not like that. Because at 12:37, the rupture disc blows and releases into the atmosphere a quantity equivalent to those two tons of sodium phenate, of dioxin, okay? Because an exothermic reaction started for a reason not clearly understood, although there is an article by Meaker here, a journal, the most prestigious journal out there, from 1980, which does a thermodynamic analysis and shows that a hotspot was created, that theoretically it's possible for hotspots to form within the reaction mixture, and that this hotspot initiated the exothermic reaction. It was something unknown. So, there is serious fault, naturally, but these were still unknown things. The message to take home is that if you know what's happening, you have a chance to get out of it, and it's not guaranteed that you have understood everything that's involved in a given chemical reaction. So, you need to know more, you need to study more, and understand all the connections. Let's move on. We'll finish soon. Bhopal, you know what Bhopal is? And here we talk a bit about chemistry from another perspective. This is simply the largest chemical disaster that has occurred in the last 100 years, I think. Bhopal, India. Have you heard of it? I hope so. But 3,800 people died immediately, and in the following days, about ten thousand, and then all the long-term side effects. This is the chemistry behind the Bhopal disaster of '84. The culprit is methyl isocyanate. This molecule, circled in orange here on the slide, which is deadly and toxic. This is the process they used in Bhopal to synthesize this insecticide, which at the time was the third best-selling insecticide in the United States. Union Carbide, an American company, had delegated the production to its subsidiary in India. The synthesis involved... oh, here's the methylamine, the formation of isocyanate from these reagents. Do you know what this is? It should remind you of something, no? So, they lost the phosgene, they made methyl isocyanate from these reagents, methyl isocyanate, and they made the synthesis, you see, simply the formation of this carbonate, which was used as an insecticide. The point is that methyl isocyanate had to be accumulated to then be used as a reagent in the next stage. On the right is the "idiot" alternative. Using the same reagents, phosgene, which is not a nice thing to use, but in those years it was still used. Chloroforiminate is formed, okay? Chloroforiminate is then reacted with methylamine to obtain the exact same product. In this case, methyl isocyanate is not accumulated, and the problem would not arise. Because they didn't use this technology. Perhaps it wasn't consolidated, perhaps it was more expensive, perhaps they imported plants that already worked like this, and no one bothered to improve it. So, you see, the step between black chemistry and semi-green chemistry is not difficult. You just need to change the order of addition of the reagents, for example. Is it clear to everyone how chemistry works? You all did Organic Chemistry 2. Trivial chemistry, but the consequences were dramatic. You can do even better than this if you want to synthesize the same thing. And indeed, there are two processes that, instead of using phosgene, which is a nerve gas used in World War I, use reagents that are extremely safer, like dimethyl urea, for example. So, you start from phenol and methyl urea in a single step, you can obtain carbaryl, this intermediate they were looking for, or from this, what is it called? Methyl formate. Methyl formate. Phosgene. You see, you move forward. So, here is an economic analysis that shows how the cost of reagents, we are not talking about plant costs, contributes to determining choices in this case, incorrectly. So, the synthesis via methyl isocyanate, which caused the disaster in Bhopal, plus phosgene to give the product. If you calculate how much each reagent costs per kilo, how many moles are used, you see, 2.50 euros per kilo for methyl isocyanate, 2.50 dollars for phosgene. Carbaryl is sold at 5.80. So, the profit, just in terms of reagent costs, for one kilo of carbaryl, you earn 2.24 dollars. From an environmental point of view, this "super green" synthesis, so to speak, much more environmentally sustainable, much safer, is not necessarily more environmentally sustainable. It's extremely different, no? It's more or less the same. You earn slightly more because methyl formate is cheap, phosgene is expensive. It costs exactly the same. You need a hydrogenation step somewhere, some hydrogenolysis somewhere, and you get a product that is worth exactly the same as before. So, the economic advantage of doing green chemistry, if you only look at the price of reagents and not the price of the plant, which was obviously already there, does not justify the choice of a dangerous chemistry. What is the message we take away from here? That if you can use safer reagents, not dangerous intermediates, not dangerous reaction conditions, you can do it. Only if you think of alternatives. And who thinks of alternatives? Engineers, no? Chemists. The engineer who can build a reactor that doesn't explode. It won't always be subject to the danger of exploding. If you develop safe chemistry, even if the reactor explodes, nothing happens. Let's read this. This is a bit of a "bla bla" example of how the perception of the population must be taken into account. This is in China in 2005. So, you were there. An explosion in a chemical plant. The residents of Jilin City were evacuated, not because they were informed by the government, but simply because they understood what the problem was. The government denied that any chemical compounds were released into the air after the explosion, and that the explosion had only produced CO2 and water. The owners of the company declared that the company had not released any chemical products into the river that flows there. After the next day, 24 hours later, they began to supply the city with water from cisterns. Actually, no, sorry. They continued to draw drinking water from the river, etc., etc. But they noticed that there was a lot of foam on the water, and that the water used to cool the fire, to extinguish the fire, contained benzene, okay? So, what happened is that some benzene tank exploded there, releasing enormous quantities of benzene into the river and into the sewage system. Obviously, the river flows and carried all the benzene contained in it downstream. So, here it's not so much about understanding chemistry. It's about perception and the necessary measures to intervene, to inform the population, to safeguard health. It's not technically green chemistry, but it's something a chemist must understand, must know. So, chemistry must also be used to avoid these inconveniences. This is just to say that in our country, things don't always go better. But this was an incident that was contained. In Germany, okay, along the Rhine, it simply caught fire.
The cracking mixture in this a few years ago a couple of 23 years ago was all over the news but you see how the perception was different 2016 was on the front pages of all the newspapers it was the opening news of all the TV broadcasts because there is the perception that whatever happens a chemical plant can be potentially serious in this case it was not particularly serious they closed everything for a month or two and then they reopened the cracking was simply a cracking plant identical to the one that is in Marghera there had been a leak in a transfer line and hydrocarbons had caught fire so nothing even particularly toxic or dangerous but this too must be taken into account not just disasters unless I can think of some other one so the dangers associated with chemicals with chemical processes are toxicity to humans pollution for the environment and then the danger of explosions of serious accidents that can always happen pollution is spoken of chemical waste and so we enter the realm of chemical production solvents metals from catalysts and byproducts and we will talk about them extensively during the course so when there is a chemical reaction it is inevitable or almost that solvents are involved it is inevitable that catalysts are involved it is inevitable that byproducts are involved no think about the organic chemistry lab you did with me do you remember how many solvents we used you used ether you used acetone you used methane you used it hexane you used petroleum ether did someone I used carbon disulfide Chiara used sulfur I remember what needed to be distilled off under vacuum solvents are ubiquitous in the use of chemistry they are a problem because there are many and we will talk about catalysts catalysts that derive from metals the reaction we did with a metal in the graphics lab 2 connected to the topics there is now the Grignard reaction with magnesium magnesium is a calm metal and it is not always a metal that you cannot discharge into the water okay byproducts when you did the extractions the aqueous phase you threw it in the bin right and that bin someone has to dispose of it it's not that you threw everything away and you threw the waste down the sink so it's just to give you the perspective that even simple operations you do in the lab must be controlled once upon a time things were thrown down the sink now it's not done it's not thrown down the sink products must be managed so if I generate for every gram of Grignard chemical product I make I generate a kilo of solvents waste water silica junk that must be accounted for in the environmental cost of the reaction you did in the beginning of "luscianese solutions to pollution" which sounds like a tongue twister what does pollution mean this was the initial attitude at the beginning of the era of environmental legislation the idea was that substances could be released into the environment as long as they were sufficiently diluted so as not to cause problems or to cause dangers to the environment does all this make sense it could have been true once when production was limited clearly whether you dilute it or not in the end the absolute quantity you throw out into the environment that's right okay where do I stop