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CHAPTER I Introduction This is a book about chemistry. It tells how chemistry fits into our lives. It tells of new chemical frontiers that are being opened, and what benefits may flow from them. It tells how much chemistry contributes to our existence, our culture, and our quality of life. This book shows how central chemistry is among the sciences as they are applied to human needs. It shows how important chemicals are to our survival. And just what is a chemical? Perhaps you have your answer ready DDT, Agent Orange, and dioxin are chemicals. Yes, indeed they are, just as much as sugar and salt, air and aspinn, milk and magnesium, protein and penicillin are chemicals. We ourselves are made up entirely of chemicals. But what of the changes that we see around us: iron nails rust, grass grows, wood burns? Here we see one set of chemicals turning into another set of chemicals. Chemistry is the science concerned with such changes. Without these changes, that is, chemical reactions, Earth would be a lifeless planet. A bean plant takes carbon dioxide from the air and water from the soil to produce carbohydrates through a wondrous series of chemical reactions called photosynthesis. All living processes are chemical reactions. And all of the things we use, wear, live in, ride in, and play with are produced through controlled chemical reactions. That is the business of chemists: to design reactions that will convert chemical substances we find around us into chemical substances that serve our needs. We want silicon transistors for our computers, but we find no silicon as such in nature. Instead, we find silica, in the form of sand, on every beach. Through chemistry, silica is converted to elemental silicon. We want a chemical substance that will be effective against Parkinson's disease. Chemists respond by synthesizing the chemical carbidopa, a substance not found in nature, but extremely effective in medical therapy. Drivers want to burn millions of gallons of fuel every day with minimal exhaust contami- nation of the atmosphere. A part of the answer is found in your automobile's catalytic exhaust converter, and the rest in marvelous chemical manipulations of the raw materials we have at hand, crude oils, which are converted on a gigantic scale into refined chemicals that burn efficiently in your auto engine. Chemists manage to answer so many needs of our society through a deep understanding of the factors that govern and furnish control of chemical reactions. These understandings are rooted in a powerful concept called the atomic theory in 1
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2 INTRODUCTION which all substances are considered to be made up of submicroscopic particles called atoms. There are a hundred or so chemical types of atoms, each type with its own behavioral characteristics. These are the "elements." Atoms have character- istic abilities to combine with each other to form identifiable groups of atoms, called molecules. Each of these molecules has its own set of properties. These are `'compounds. " How well this atomic theory works is demonstrated by the accomplishments of chemists guided by it. Over seven million different molecular compounds have been synthesized, and the rate of discovery is increasing every year. Only a small fraction of these are found in nature most of them were de- ~ 8 coo ooo o CL 8 6,ooo coo c e 4oooooc _ o _ 8 2,ooo,ooo As ,~ _' 1 · ~ ~ I I · · · ~ I ~ 000 Year CHEMICAL KNOWLEDGE IS GROWING RAPIDLY liberately designed and synthe- sized to meet a human need or to test an idea. This book tells about the impact of this grow- ing capability on our society. It shows that chemistry plays a critical role in man's attempt to feed the world population, to tap new sources of energy, to clothe and house humankind, to provide renewable substitutes for dwindling or scarce maten- als, to improve health and con- quer disease, and to monitor and protect our environment. It shows that there are rich opportunities in chemistry for advances through basic research that win help future generations deal with their evolving needs. Because of this responsiveness to human needs, chemistry has become a crucial factor in the nation's economic well-being. Equally important, our culture believes that learning about our place in the universe is enough reason for encouraging scientific inquiry. For example, nothing concerns humans more than questions about the nature of life and how to preserve it. Because all life processes are brought about by chemical changes, understanding chemical reactivity is a neces- sary foundation for our ultimate understanding of life. Thus, chemistry, along with biology, contributes to human knowledge in areas of universal Dhilosonhical . ·— slgnlncance. Fortunately, we find ourselves in a time of special opportunity for advances on the many fronts of chemistry. The opportunity comes from our developing ability to probe the basic steps of chemical change and, at the same time, to deal with the extreme molecular complexity of biological molecules. A recurrent theme will be the use, by chemists, of the most sophisticated and advanced instrumental techniques that contribute significantly to chemistry's accelerating progress. We hope that your reading will be enjoyable, that it will give you a new view of the beneficial role of chemistry in your life, and that some of you will look to chemistry for a fulfilling and rewarding career.
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CHAPTER II Env~onmontd Quality Tbrou~b Cbemis~y
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1 No Deposit, No Return, No Problem Each year in this country, you and I dump millions of tons of plastics into the environment. A high percentage of that is spewed directly into the oceans. In fact, 9 million tons of the solid waste produced in the United States each year goes directly into the sea. Merchant ships alone dump 6.6 million tons of trash overboard each year— that's enough garbage to fill 440,000 classrooms! Contrary to the beliefs of many, plastic debris does eventually degrad~but it may take up to 50 years. A lot of litter can accumulate in that stretch of tune. Marine environments are particularly sensitive to this proble~plastic trash floats aIld is mistaken for jellyfish or eggs or other dinnertime treats by marine animals. In addition, sea animals become entangled in plastic waste, including the 150,000 tons of plastic fishing gear that is discarded in the ocean each year. Another unhappy twist to this problem can be seen in the arctic regions, where litter accumulates, but is inhibited r from biodegradation because of the very low temperatures. : Chemists have taken a big step toward alleviating this distressing TIC ~ problem. The remedy lies in the construction of the plastic itself. Em\ Plastics are polymers made from petroleum-based compounds. :\ . - at\ They consist of long chains of repeating molecular groups. W\ .. \ Chemists have found several ways to make changes in the plastic molecules so that they are more in tune with our environmental needs. One way Is to chemically attach light-sensitive molecular groups at regular intervals in the macrornolec- ular chain. When plastic made from this polymer is exposed to sunlight, these light- sensitive groups absorb radiation and i,_ cause the polymer to break apart at these A_ points. Then Nature does the rest. The small segments which result are easily biodegradable. Presto ! Photo- degradable plastics! Insertion of ketone groups into common polymers (such as polystyrene and polyethylene) has been of particular interest as photodegradable matenals. Such ketone-substituted polymers are stable in artificial __^ _ light and only undergo photochem~cal reactions when irradiated i? -Phi—Hi\ with shorter wavelengths of light like that from the sun. ^~ a\ Another way to tailor long plastic molecules to suit Nature's needs has been to introduce molecular W - ~ ~ groups that are considered delectable by certain \~ microorganisms in the environment. These mi- __\~. ~ croscop~c munchers then do the work of ~ ~~` breaking the long molecules into smaller if, ~ bits. Hopefully, with innovations like these, - ~ our plastic waste problem will someday be ~ going, going, gene. 4
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