(a) Na , (b) Cl . (c) F , (d) H . (e) Ca 2 , (f) S 2 . (g) O 2 . (h) Br , These compounds are all natural products, and many advances in modern society are the result of their study and use. Capsaicin, it turns out, is an effective analgesic. It can modulate pain when applied to the skin and is currently sold under the tradename Capzacin. Salicylic acid is a painkiller as well as an anti-acne medication, while lovastatin is used as a drug to decrease levels of cholesterol in human blood. The power of modern organic chemistry lies in the ability to take such molecules, sometimes found in trace quantities in nature, and make them from readily available and inexpensive start- ing materials on a large scale so that all members of society can benefit from them. For instance, although we can obtain vitamin C from eating certain fruits, chemists can make large quantities in the laboratory for use in daily supplements; while some may think that “natural” vitamin C is healthier, the “syn- thetic” compound is equally effective since they are exactly the same chemically. Perhaps more important, organic chemistry also provides the opportunity to change the structures of these and other nat- ural products to make molecules with different, and potentially even more impressive, properties. For example, the addition of a few atoms to salicylic acid through a chemical reaction is what led to the discovery of aspirin (see Chapter 17), a molecule with far greater potency as a painkiller and fewer side effects than nature’s compound. Similarly, scientists at Parke–Davis Warner–Lambert (now Pfizer) used the structure and activity of lovastatin as inspiration to develop Lipitor, a molecule that has saved countless lives by lowering levels of cholesterol in human serum. In fact, of the top 20 drugs based on gross sales, slightly over half are either natural products or their derivatives. To learn more about these topics, see: 1. Nicolaou, K. C.; Montagnon, T. Molecules that Changed the World . Wiley-VCH: Weinheim, 2008 , p. 366. 2. Nicolaou, K. C.; Sorensen, E. J.; Winssinger, N, “The Art and Science of Organic and Natural Products Synthesis” in J. Chem. Educ . 1998 , 75 , 1225–1258. /
50 CHAPTER 1 THE BASICS: Bonding and Molecular Structure LEWIS STRUCTURES 1.30 Write a Lewis structure for each of the following: (a) SOCl 2 (b) POCl 3 (c) PCl 5 (d) HONO 2 (HNO 3 ) (a) CH 3 9 O 9 S 9 O O O CH 3 9 S 9 O O O (c) (d) O 9 S 9 O O O (b) CH 3 9 S 9 CH 3 O 1.31 Give the formal charge (if one exists) on each atom of the following: 1.32 Add any unshared electrons to give each element an octet in its valence shell in the formulas below and indicate any formal charges. Note that all of the hydrogen atoms that are attached to heteroatoms have been drawn if they are present. (a) (b) (c) (d) (e) N N H O N N N S O O N H F O Cl Br B Br N O Cl H S O O STRUCTURAL FORMULAS AND ISOMERISM 1.33 Write a condensed structural formula for each compound given here.
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