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1、Introduction to Organic ChemistryOrganic chemistry was born in 1828 when Friedrich Wohler attempted to synthesize ammonium cyanate (氰酸铵), NH4CNO, and obtained urea (尿素) O NH2 CNH2Instead, Wohler, who had studied to be a doctor of medicine before he decided to become a chemist, discovered that the co
2、mpound 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 frien
3、d, I must tell you that I can make urea without the use of kidneys, either man or dog. Ammonium cyanate is urea. Wohlers 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 i
4、n 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
5、 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
6、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 support
7、ed 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 pancre
8、atic(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,
9、 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
10、(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 ad
11、dictive. 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 develope
12、d 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 in
13、dustry. 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 boxe
14、s 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 e
15、arly 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 Swedi
16、sh 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 di
