Introduction to Organic Chemistry
Organic chemistry was born in 1828 when Friedrich Wohler attempted to synthesize ammonium cyanate (氰酸
铵), NH4CNO, and obtained urea (尿素)
O
‖
NH2 CNH2
Instead, Wohler, who had studied to be a doctor of medicine before he decided to become a chemist, discovered
that the compound he had made was identical with urea recovered from urine. Up to that time, scientists had
thought that the compounds present in living plants and animals could not be synthesized in the laboratory from
inorganic reagents. Wohler recognized the importance of his experiment and wrote to a friend, "I must tell you
that I can make urea without the use of kidneys, either man or dog. Ammonium cyanate is urea. "
Wohler's discovery was important because it gave impetus to a long series of experiments in which chemists
probed the nature of the chemical substances that exist in living organisms and in petroleum and coal, which are
formed from the remains of certain plants and animals that lived in the distant past. As early chemists struggled
to isolate and purify the components of plants, animals, coal, and petroleum, they observed that many of the
compounds that they isolated were composed of carbon and hydrogen. Many contained, in addition,
nitrogen(氮), oxygen, sulfur(硫), and phosphorus(磷). Chemists quickly recognized that the chemistry of carbon
was associated with life in a special way that distinguished that element from all others. Compounds of carbon
were called organic compounds to reflect their origin in living systems and to distinguish them from the
inorganic compounds, the acids, bases, and salt, derived from the other elements on the periodic table (元素周
期表).
Organic chemistry is recognized today as an area of study central to many disciplines. Life processes are
supported by the chemical reactions of complex organic compounds such as enzymes(酶), hormones, proteins,
carbohydrates(碳水化合物), and lipid(脂). The lipid cholesterol(胆固醇); hormones such as cortisone(皮质酮), and
testosterone(睾丸激素); glucose(葡萄糖), the most important source of energy in our bodies; and the
pancreatic(胰腺的) enzyme chymotrypsin(胰凝乳蛋白酶), which is essential to our digestion, are among the
compounds the structures and chemistry of which we will explore. Cells divide and grow in part according to
signals carried and transmitted by giant organic molecules called deoxyribonucleic acids(脱氧核糖核酸), DNA,
and ribonucleic acids(核酸), RNA(核糖核酸). An understanding of organic chemistry is essential to the study of
the biological and medical sciences.
Chemists, in attempts to improve on nature, have created millions of organic compounds that did not exist in
nature originally. The local anesthetic Novocain(奴佛卡因局部麻醉剂), for example, was developed to mimic the
numbing effects of the natural alkaloid(生物碱) cocaine. The search continues for a synthetic painkiller that gives
the merciful relief from pain afforded by natural opiates(麻醉剂) such as morphine without having the
undesirable side effect of being addictive. The discovery in recent years that the brain manufactures
endorphins(多肽，内啡肽), compounds that interact with the same sites in the brain as morphine does, is an
exciting new development in our understanding of how the body copes with pain. Industrial chemists, on the
other hand, have developed synthetic rubber, Neoprene(氯丁橡胶), and synthetic silks, such as rayon(人造纤维)
and nylon, to improve on the proper ties of the natural substances and to meet shortages of natural supplies.
Crude petroleum is converted by organic reactions into fuels that supply energy for heat, transportation, and
industry. Petroleum is also the chemical basis for giant molecules engineered to have properties that are useful.
Food additives, dyes, artificial flavorings, artificial sweeteners, preservatives, and pesticides, most of the
organic compounds, make the headlines in newspapers with regularity. The boxes our crackers and cereals
come in carry the abbreviations BHT(丁化羟基甲苯) and BHA(丁化羟基茴香醚) to designate organic chemicals that
keep the food from becoming rancid. The carcinogenicity(致癌力) of saccharin (糖精)and whether the use of it
should be banned is a major political as well as scientific issue.
The early organic chemists were confronted with many puzzles. They determined molecular formulas for the
compounds that they had recovered from natural sources. As early as 1824 they discovered that several
compounds with very different properties might have the same molecular formula. In 1830, the Swedish
chemist Jakob Berzelius named such compounds "isomeric bodies" from the Greek word isos, meaning "equal"
and meros, meaning "part". This discovery intensified investigations into the nature of the forces that held
atoms together and the ways in which chemical bonds could be symbolized in writing. A lively debate over these
issues continued through the middle of the nineteenth century. Many different ways of representing the
structures of molecules were proposed, disputed, and discarded.
Analyses of organic compounds provided empirical ratios of the weights of carbon, hydrogen, oxygen, and
nitrogen. However, exact molecular formulas could not be assigned until a uniform and correct set of atomic
weights was adopted by chemists. The Italian chemist, Stanislav Cannizzaro, proposed a system of
experimentally accurate atomic weights in 1860. The gradual acceptance of his system made it possible for
chemists to assign correct and universally recognized molecular formulas. This advance in turn allowed ideas
about bonding and structure to develop.
In the early nineteenth century, chemists also experimented with the transformation of one chemical substance
into another. As a result of these experiments, they observed that there were some structural units that were
carried unchanged from one reaction to another. The recognition of these intact structural units, which they
called radicals, enabled chemists to manipulate chemical substances with more precision. The art of organic
synthesis was born. Chemists could use new pathways to construct compounds that already existed in nature,
or they could create entirely new compounds.
By the end of the nineteenth century, the science of organic chemistry was flourishing. Serious study of the
structural and chemical properties of the compounds of carbon had resulted in important discoveries about the
chemistry of carbohydrates and proteins. Chemists had tackled the problems of representing the structures of
organic compounds. They had wondered how molecules looked in three dimensions and had arrived at pictures
remarkably similar to the ones we still use. Many organic compounds that did not exist in nature had been
synthesized.
The next significant step forward in organic chemistry took place in the 1920 sand 1930s. During these years,
chemists explored the exact details of chemical transformations. They began to ask questions about the relative
timing of the breaking and forming of bonds during chemical reactions. Chemists were also concerned with how
the shapes of molecules, that is, their spatial properties, affected chemical reactivity. The question of
three-dimensionality in reactions turned out to be a central one in biochemistry, the study of chemical
transformations in living organisms.
While chemists were asking more and more subtle questions about chemical reactions, new instruments that
extended their powers of observation were invented. These new instruments and techniques made it possible to
probe more deeply into the processes of nature. The number of experimental observations that could be
collected multiplied rapidly.
The progress of chemistry as a science depends on the experimental manipulations of substances in the
laboratory leading to the observation of new phenomena. In thinking about these phenomena chemists arrive
at ideas about the nature of the chemical substances under investigation. New experiments and new
observations test these ideas. The range of manipulations and observations available to the chemist has
expanded enormously in recent years. The power that chemists have to transform chemical compounds into
new ones, sometimes useful and sometimes harmful, has also increased.
Chemists have refined the way they visualize and think about the submicroscopic units called atoms and
molecules. They have created models that help them to picture and understand experimental facts about
chemical substances. Human beings are constantly creating and refining the models they use in dealing with the
physical world. Some models are pictorial; others are more abstract and mathematical. Some models are widely
adopted because they are useful; others are quickly modified on the basis of new observations.
Read the text quickly and answer the following questions and choose the best answer from the
four choices marked A), B), C) and D).
1. What does the author mean by saying that "organic chemistry was born in 1828 when
Friedrich Wohler attempted to synthesize ammonium cyanate, NH4CNO, and obtained urea"?
A. Friedrich Wohler finally obtained urea.
B. Urea only exists in human body.
C. Chemists were inspired to probe the nature of the chemical substances that exist in
living organisms and in petroleum and coal.
D. Life processes are supported by the chemical reactions of complex organic compounds.
2. According to the text, which of the following is essential to our digestion?
A. testosterone
B. enzyme chymotrypsin
C. proteins
D. glucose
3. According to the text, which of the following is true of synthetic painkiller?
A. They are organic compounds which exist in nature.
B. They are developed to mimic the numbing effects which can give the merciful relief
from pains.
C. The employment of them will cause undesirable side effect of being addictive.
D. They are regarded as exciting new development in our understanding of how the body
deals with pain.
4. Which of the following scientists proposed the system of accurate atomic weights which
made it possible for chemists to assign correct and universally recognized molecular formula?
A. Albert Einstein
B. Friedrich Wohler
C. Jakob Berzelius
D. Stanislav Cannizzaro
5. Which of the following discoveries intensified investigations into the nature of the forces
that held atoms together and the ways in which chemical bonds could be symbolized in writing?
A. The discovery that several compounds with very different properties might have the
same molecular formula.
B. cholesterol and cortisone
C. Wohler's discovery of synthetic urea
D. the carcinogenicity of saccharin
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