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Objective:

After reading this unit, you should able to Know what organic chemistry is.

Know how to understand organic chemistry.

Know the organic chemistry keywords.

READING 1

Organic chemistry is the study of those carbon-containing molecules known as organic compounds, which are based upon long chains or rings of carbon atoms. Over 6 million organic compounds are known today and the possibility exists for countless more to be discovered and synthesized. Organic chemists determine the structure of organic molecules, study their various reactions and develop procedures for the synthesis of organic compounds. Organic chemists have had a profound effect on modern life: It has improved natural materials and it has synthesized natural and artificial materials that have, in turn, improved health, increased comfort, and added to the convenience of nearly every product manufactured today.

TASK 1: COMPREHENSION QUESTIONS Answer the questions below.

1. What are organic compounds?

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2. What is the job of an organic chemist?

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3. Give an example to illustrate that organic chemists have had a profound effect on modern life.

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READING 2

All organic compounds are primarily divided into two large groups: acyclic compounds – with an open chain and cyclic compounds – with a closed chain.

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Acyclic compounds are also called fatty or aliphatic (from a Greek word meaning fat) since fats and fatty acids belong to this class. These compounds may have a ―normal‖ structure, i.e., have an unbranched skeleton similar to the skeleton of normal pentane or a branched skeleton (with various degree of branching), such as isopentane.

Cyclic compounds are classified in isocyclic, in which there is a cyclic grouping consisting of several carbon atoms closed into a ring and heterocyclic, in which the ring includes one or more atoms other than carbon (heteroatoms). A special position among such cyclic compounds is occupied by so-called aromatic compounds, six-membered rings containing alternating three single and three double carbon-carbon bonds or bonds between a carbon atom and a heteroatom.

TASK 2: TRUE OR FALSE

Decide whether the following statements are true (T) or false (F).

1. Organic compounds are classified according to their structural formulas, the spatial arrangement of the atoms.

2. The word ―fat‖ is derived from the Greek language.

3. Acyclic compounds can be either saturated or unsaturated fatty compounds.

4. An aliphatic compound of ―normal structure‖ is one which has a branched-chain structure.

5. Heterocyclic compounds consist of hydrocarbons arranged in a ring.

6. Isocyclic compounds with alternating double carbon-carbon bonds are aromatic compounds.

TASK 3: GAP FILLING

Complete the passage with appropriate words below

chains aromatic

heterocyclic

ring aliphatic

hydrogen atoms

structure hydrocarbons

heterocycles

1. Organic compounds are classified according to their (1)………., this classification being based on the character of the carbon skeleton of (2)………….., i.e., the sequence of carbon atoms linked to one

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another. Compounds that contain atoms other than carbon are regarded as derivatives of hydrocarbons, in which (3)………. are replaced by such atoms called heteroatoms. An exception is made for such structure in which the heteroatom closes the (4)………. Of carbon atoms into a (5)………….. Such cyclic or ring compounds are classified as a special class of compounds termed (6)………..

2. Some of the classes of substances studied in organic chemistry include (7)……….. compounds, chains of carbon which may be modified by functional groups; (8)………. Hydrocarbons compounds containing one or more benzene rings; (9)……….. compounds, which include non-carbon atoms as parts of a ring structure and polymers, which are long (10)………….of repeating groups or so-called monomers.

READING 3

Organic chemistry is a broad field which intersects with such diverse areas as biology, medicine and pharmacology, polymer technology, agriculture, and petroleum engineering. At the heart of organic chemistry are fundamental concepts of molecular structure and reactivity of carbon-containing compounds. The purpose of this text is to explore this central core, which is concerned with how the structures of organic compounds are related to reactivity. Reactivity, in turn, determines the methods that can be used for synthesis. Understanding of structure, reactivity, and synthesis can be used within organic chemistry or applied to other fields, such as those named above, which require contributions from organic chemistry. Structure includes the description of bonding in organic molecules and the methods for determining, analyzing, and predicting molecular structure. Dynamic aspects of structure, such as conformational equilibria, are also included. Stereochemistry is also a crucial aspect of structure in organic chemistry. Reactivity pertains to the aspects of a given structure that determine its chemical transformations. Is the molecule electron-rich or electron-poor? Is it easily reduced or oxidized? What is the distribution of the most reactive electrons? Which bonds are weakest and therefore most likely to engage in reactions? Unlike structure, which is an inherent property of the molecule, reactivity usually describes an interaction with other molecules. Understanding reactivity includes describing the mechanisms, that is the stepwise process by which reactions occur. Reactivity also encompasses the stereochemical aspects of the transformation. Synthesis encompasses those activities which are directed toward finding methods that convert existing substances in different compounds. Synthesis involves the control of reactivity to achieve specified transformations. It involves the choice of reagents, catalysts, and reaction conditions that will accomplish a given transformation within the required parameters. In various circumstances, the limiting parameters might include yield, purity of product, stereochemical control, availability or cost of reagents, or safety and environmental consequences. Structure, reactivity, and

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synthesis are all interrelated. Synthesis is built on knowledge of both structure and reactivity, and understanding reactivity ultimately rests on detailed knowledge about molecular structure. A firm grounding in the principles of structure and chemical bonding is therefore and essential starting point for fuller appreciation of reactivity and synthesis. We will discuss the ideas that have proven most useful to organic chemists for describing and organizing facts, concepts, and theories about the structure of organic molecules.

TASK 4: MATCHING

Match a word or phrase in A with its definition in B

1) Structure determination a) how to find out how these molecules react with each other and how to predict their reactions

2) Theoretical organic chemistry

b) how to understand those structures in terms of atoms and the electrons that bind them together

3) Reaction mechanisms c) how to design new molecules - and then make them

4) Synthesis d) how to find out what Nature does and how the structures of biologically active molecules are related to what they do

5) Biological chemistry e) how to find out the structures of new compounds even if they are available only in invisibly small amounts

TASK 5: GAP FILLING

Complete the passage with appropriate words below

atom(s) chemical reaction(s) description of the reaction (3) ………. in terms of curly arrows and that is what we are about to start. The first is (4) …….. and the second (5) ………. The creation of new (2)………. is the special concern of chemistry and an interest in the mechanism of (6)………… is the special concern of organic chemistry.

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2. Organic chemistry concerns itself with the way in which these atoms are bonded together into stable molecular (1) ……….., and the way in which these (2)……… change in the course of (6)………….

3. Unlike most other elements, carbon forms strong (7)……….to other carbon (8)………. and to a wide variety of other (9) ………. Chains and rings of carbon (8)…………..can be built up to form an endless variety of (2)……... It is this diversity of carbon compounds that provides the basis for life on Earth.

TASK 6: MAIN IDEA

Which is not the main idea of the passage?

1. Organic chemistry is a field which relates to many areas, for example, biology, medicine, pharmacology, etc.

2. Structure, reactivity, and synthesis are closely connected.

3. Organic chemists must know how to describe and organize facts, concepts, and theories about the structure of organic molecules.

4. Stereochemistry is an important aspect of structure.

5. Reactivity describes the step-by-step pathway from reactants to products

TASK 7: SUMMARY

Make a summary of the interrelation of structure, reactivity, and synthesis by drawing a diagram, a table, or a map.

READING 4

The reaction of methane with chlorine produces a mixture of chlorinated products, whose composition depends on the amount of chlorine added and also on the reaction conditions. Either light or heat is needed for the reaction to take place at a useful rate. When chlorine is added to methane, the first reaction is

This reaction may continue; heat or light is needed for each step:

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This sequence raises several questions about the chlorination of methane. Why is heat or light needed for the reaction to go? Why do we get a mixture of products? Is there any way to modify the reaction to get just one pure product? Are the observed products formed because they are the most stable products possible? Or are they favored because they are formed faster than any other products? The answers to these questions involve three aspects of the reaction: the mechanism, the thermodynamics, and the kinetics.

1. The mechanism is the complete, step-by-step description of exactly which bonds break and which bonds form in what order to give the observed products.

2. Thermodynamics is the study of the energy changes that accompany chemical and physical transformations. It allows us to compare the stability of reactants and products and predict which compounds are favored by the equilibrium.

3. Kinetics is the study of reaction rates, determining which products are formed fastest. Kinetics also helps to predict how the rate will change if we change the reaction conditions.

We will use the chlorination of methane to show how we study a reaction. Before we can propose a detailed mechanism for the chlorination, we must learn everything we can about how the reaction works and what factors affect the reaction rate and the product distribution. A careful study of the chlorination of methane has established three important characteristics:

1. The chlorination does not occur at room temperature in the absence of light. The reaction begins when light falls on the mixture or when it is heated. Thus, we know this reaction requires some form of energy to initiate it.

2. The most effective wavelength of light is a blue color that is strongly absorbed by chlorine gas. This finding implies that light is absorbed by the chlorine molecule, activating chlorine so that it initiates the reaction with methane.

3. The light-initiated reaction has a high quantum yield. This means that many molecules of the product are formed for every photon of light absorbed. Our mechanism must explain how hundreds of individual reactions of methane with chlorine result from the absorption of a single photon by a single molecule of chlorine.

33 TASK 8: VOCABULARY CHECK

Find the words in the text which mean:

1. a combination of different things 2. a unit of electromagnetic energy 3. the total amount of something produced

4. the quality or state of being steady and not changing in any way 5. a measurement of the speed at which something happens

TASK 9: COMPREHENSION QUESTIONS

Answer the questions below

4. What factors does the number of the chlorinated products depend on?

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5. What are the three aspects of the reaction of methane with chlorine?

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6. What are the advantages of understanding the thermodynamics of a reaction?

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7. How can we know that energy can help initiate the chlorination of methane?

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8. What is a reaction with high quantum yield?

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TASK 10: How to find good keywords

Find the keywords in reading paragraphs 3 and 4 TASK 11: Summary

In about 5 sentences, summarize the main idea in paragraphs 3 and 4

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TASK 12: Glossary

Search your knowledge, look up your dictionary, internet or ask your instructor to clarify the definition and Vietnamese meaning of the following terminologies.

N^o Terminology Definition Vietnamese

1 structure 2 synthesis

3 acyclic compounds 4 cyclic compounds 5 aliphatic

6 fatty acids 7

S

keleton

or chain

8 branched skeleton 9 isocyclic

10 heterocyclic 11 heteroatoms 12 aromatic 13 medicine 14 pharmacology 15 reactivity 16 conformational 17 reduced 18 oxidized 19 stereochemical 20 transformation 21 parameters 22 yield 23 purity 24 rings 25 chlorination

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In document Universidad de Málaga (página 169-183)