Brief contents

Unit 1	STRUCTURE AND BONDING……………...	8
UNIT 2	PRINCIPLES, NOMENCLATURE & SYMBOLS……………………………………..	26
UNIT 3	MOLECULAR SYMMETRY………………..	40
UNIT 4	STEREOCHEMISTRY OF REACTIONS….	53
UNIT 5	RESOLUTION OF ENANTIOMERS………	64
SUPPLEMENTARYTEXTS
	1 PRINCIPLES OF STEREOCHEMISTRY.	84
	2 ENANTIOMERIC RELATIONSHIPS……	85
	3 DIASTEREOMERIC RELATIONSHIPS...	94
	4METHODS OF DETERMINING CONFIGURATION……………………………...	113
	5 The Cause of Optical Activity……..	116
	6 Molecules With More Than One Chiral (Stereogenic) Center………...	117
	7 Asymmetric Synthesis………………...	122
Business English
	WRITING  BUSINESS  LETTERS…………	128
	Formal letter…………………………..	132
	Informal letter or email…………	137
	writing a tactful advice letter	143
	HOW TO WRITE A REQUEST LETTER…	145
	COMPLAINT LETTER……………………...	148
	WRITING CLAIM LETTER………………..	149
	INQUIRY LETTER…………………………..	151
APPENDICES
	1 EXCLAMATIONS………………………….	158
	2 GENERAL CONVERSATION GAMBITS	158
	3THE SCHEME OF RENDERING THE TEXT…………………………………………..	162
	4 FLOW CHARTS……………………………	164
	5 GRAPH……………………………………...	167
	6 READING AND INTERPRETING GRAPHS………………………………………	169
	7 PRESENTATIONS…………………………	175
TAPESCRIPTS	………………………………………………….	179
BIBLIOGRAPHY 1	…………………………………………………..	200
BIBLIOGRAPHY 2	………………………………………………….	200

Unit 1 structure and bonding

Reading

Section A

1. You are going to read three texts which are all connected with chemistry. Read the texts and be able to make intelligent guesses about:

- where the text came from.

- who the text has been written for.

- why it has been written.

Text A

What is organic chemistry? The answer is all around. The proteins that make up our hair, skin, and muscles; the nucleic acids, RNA and DNA, that control our genetic heritage; the foods we eat; the clothes we wear; and the medicines we take—all are organic chemicals.

The foundations of organic chemistry were built in the mid-eighteenth century as chemistry was evolving from an alchemist's art into a modern science. At that time, unexplainable differences were noted between sub­stances derived from living sources and those derived from minerals. Com­pounds from plants and animals were often difficult to isolate and purify. Even when pure, these compounds were difficult to work with and were more sensitive to decomposition than compounds from mineral sources. In 1770, the Swedish chemist Torbern Bergman first expressed this difference between "organic" and "inorganic" substances, and the phrase organic chemistrysoon came to mean the chemistry of compounds from living organisms.

To many chemists at the time, the only explanation for the difference in behavior between organic and inorganic compounds was that organic compounds contained a peculiar and undefinable "vital force" as a result of their coming from living sources. One consequence of the presence of this vital force, chemists believed, was that organic compounds could not be prepared and manipulated in the laboratory as could inorganic compounds.

Although the vitalistic theory was believed by many influential chem­ists, its acceptance was by no means universal, and it's doubtful that the development of organic chemistry was much delayed. As early as 1816, the theory received a heavy blow when Michel Chevreul found that soap, pre­pared by the reaction of alkali with animal fat, could be separated into several pure organic compounds, which he termed "fatty acids." Thus, for the first time, one organic substance (fat) had been converted into others (fatty acids plus glycerin) without the intervention of an outside vital force.

A little more than a decade later, the vitalistic theory suffered still further when Friedrich Wohler discovered in 1828 that it was possible to convert the "inorganic" salt ammonium cyanate into the previously known "organic" substance urea.

By the mid-nineteenth century, the weight of evidence was clearly against the vitalistic theory. In 1848, William Brande wrote in a paper that: "No definite line can be drawn between organic and inorganic chem­istry . . . any distinctions . . . must for the present be merely considered as matters of practical convenience calculated to further the progress of stu­dents." Chemistry today is unified; the same basic scientific principles that explain the simplest inorganic compounds also explain the most complex organic molecules. The only distinguishing characteristic of organic chem­icals is that all contain the element carbon.Nevertheless, the division between organic and inorganic chemistry, which began for historical rea­sons, maintains its "practical convenience ...to further the progress of students."

Organic chemistry, then, is the study of carbon compounds. Carbon, which has atomic number 6, is a second-period element whose position in an abbreviated periodic table is shown in Table 1.1. Although carbon is the principal element in organic compounds, most also contain hydrogen, and many contain nitrogen, oxygen, phosphorus, sulfur, chlorine, and other elements.

Why is carbon special? What is it that sets carbon apart from all other elements in the periodic table? The answers to these questions are complex but have to do with the unique ability of carbon atoms to bond together, forming long chains and rings. Carbon, alone of all elements, is able to form an immense diversity of compounds, from the simple to the staggeringly complex: from methane, containing one carbon, to DNA, which can contain hundreds of billions. Nor are all carbon compounds derived from living organisms. Chemists in the past 100 years have become extraordinarily sophisticated in their ability to synthesize new organic compounds in the laboratory. Medicines, dyes, polymers, plastics, food additives, pesticides, and a host of other substances—all are prepared in the laboratory, and all are organic chemicals. Organic chemistry is a science that touches the lives of all; its study can be a fascinating undertaking.

Text B

Think for a moment about the stuff of everyday life. We drive cars powered by gasoline or diesel fuel. We cook chicken on a grill that burns propane. We live in homes heated directly by the burning of natural gas or fuel oil, or in electrically heated homes, for which most electricity is produced by the combustion of a fossil fuel. All of these fuels are organic compounds, and they are used as fuels because their combustion reactions with oxygen to produce CO2 and H20 are highly exothermic.

The great majority of medicines used to treat everything from headaches to strokes, to control diabetes, and to combat cancer are organic compounds. Whether they are natural products derived from living plants or animals, or synthetic materials prepared in the laboratory, the products of the pharmaceutical industry are compounds of carbon.

Your favorite soft T-shirt is made of cotton; the soles of your running shoes are made of a synthetic rubber. Cotton is an organic natural fiber produced by a plant. Because of the composition, shape, and orientation of the large molecules that form cotton fibers, the material is soft and absorbent. Synthetic rubber is a polymer, manufactured from compounds of carbon and hydrogen derived from crude oil. Because of the size, shape, and orientation of the polymer molecules in synthetic rubber, the material is springy, nonabsorbent, and resistant to abrasive contact with surfaces.

Fans at a hockey game sit on molded plastic seats and watch goalies wearing helmets of impact-resistant Kevlar. We pour sodas out of plastic bottles and drink them from Styrofoam cups while eating sandwiches wrapped in plastic wrap.

Plastics, Kevlar, Styrofoam and cling wrap are made from compounds derived from crude oil. The plastic seat is strong, light, and capable of bearing considerable weight without breaking. The goalie's helmet must be light-weight and able to withstand the impact of a hockey puck moving at speeds close to 100 miles per hour. Soda bottles must resist punctures and prevent CO2 from escaping, the Styrofoam cup must be a poor conductor of heat so that beverages in it stay hot or cold, and the sandwich wrap must be flexible and prevent oxygen from reaching the sandwich. All these properties can be designed into the materials at the molecular level, because the physical properties of these materials are directly linked to their structure and composition.

Apart from our bones and teeth, and the water and electrolytes that form the basis of bodily fluids, we humans are all composed of carbon compounds. The great bulk of the food we eat is made up of carbon-containing molecules, too. Compounds of carbon are everywhere, and they are so varied in size, shape, and properties that an entire field within chemistry is devoted to their study. A knowledge of organic chemistry is fundamental and essential for a scientific understanding of fuels, foods, pharmaceutical agents, plastics, fibers, living creatures, plants, indeed almost everything we are, almost everything we need to survive, and almost everything we have produced that makes our lives easier in the modern world.

Text C

When you awoke this morning, a flood of chemicals called neurotransmitters was sent from cell to cell in your nervous system. As these chemical signals accumulated, you gradually became aware of your surroundings. Chemical signals from your nerves to your muscles propelled you out of your warm bed to prepare for your day.

For breakfast you had a glass of milk, two eggs, and buttered toast, thus providing your body with needed molecules in the form of carbohydrates, proteins, lipids, vitamins, and minerals. As you ran out the door, enzymes of your digestive tract were dismantling the macromolecules of your breakfast. Other enzymes in your cells were busy converting the chemical energy of food molecules into adenosine triphosphate (ATP), the universal energy currency of all cells.

As you continue through your day, thousands of biochemical reactions will keep your cells functioning optimally. Hormones and other chemical signals will regulate the conditions within your body. They will let you know if you are hungry or thirsty. If you injure yourself or come into contact with a disease-causing microorganism, chemicals in your body will signal cells to begin the necessary repair of defense processes.

Life is an organized array of large, carbon-based molecules maintained by biochemical reactions. To understand and appreciate the nature of a living being, we must understand the principles of science and chemistry as they apply to biological molecules.

Chemistryis the study of matter, its chemical and physical properties, the chemical and physical changes it undergoes, and the energy changes that accompany those processes. Matteris anything that has mass and occupies space. The changes that matter undergoes always involve either gain or loss of energy. Energyis the ability to do work to accomplish some change. The study of chemistry involves matter, energy, and their interrelationship. Matter and energy are at the heart of chemistry.

Chemistry is a broad area of study covering everything from the basic parts of an atom to interactions between huge biological molecules. Because of this, chemistry encompasses the following specialties. Biochemistryis the study of life at the molecular level and the processes associated with life, such as reproduction, growth, and respiration. Organic chemistry is the study of matter that is composed principally of carbon and hydrogen. Organic chemists study methods of preparing such diverse substances as plastics, drugs, solvents, and a host of industrial chemicals. Inorganic chemistryis the study of matter that consists of all of the elements other than carbon and hydrogen and their combinations. Inorganic chemists have been responsible for the development of unique substances such as semiconductors and high-temperature ceramics for industrial use. Analytical chemistryinvolves the analysis of matter to determine its composition and the quantity of each kind of matter that is present. Analytical chemists detect traces of toxic chemicals in water and air. They also develop methods to analyze human body fluids for drugs, poisons, and levels of medication. Physical chemistryis a discipline that attempts to explain the way in which matter behaves. Physical chemists develop theoretical concepts and try to prove them experimentally. This helps usto understand how chemical systems behave.

Over the last thirty years, the boundaries between the traditional sciences of chemistry and biology, mathematics, physics, and computer science have gradually faded. Medical practitioners, physicians, nurses, and medical technologists use therapies that contain elements of all these disciplines. The rapid expansion of the pharmaceutical industry is based on recognition of the relationship between the function of an organism and its basic chemical makeup. Function is a consequence of changes that chemical substances undergo. For these reasons, an understanding of basic chemical principles is essential for anyone considering a medically related career; indeed, a worker in any science related field will benefit from an understanding of the principles and applications of chemistry.