this chapter and the next we extend our coverage of conjugated systems to include arenes. Arenes are hydrocarbons based on the benzene ring as a structural unit. Ben- are zene, toluene, and naphthalene, for example, are arenes

ntil the second half of the twentieth century, the structure of a substance-a newly discovered natural product, for example-was determined using information obtained from chemical reactions. This information included the identification of functional groups by chemical tests, along with the results of experiments in which the substance was broken down into smaller, more readily identifiable fragments. Typical of this approach is the demonstration of the presence of a double bond in an alkene by cat- nd subsequent

he next several chapters deal with the chemistry of various oxygen-containing functional groups. The interplay of these important classes of compounds-alco- hols, ethers, aldehydes, ketones, carboxylic acids, and derivatives of carboxylic acids-is fundamental to organic chemistry and biochemistry

ADDITION TO THE CARBONYL GROUP Idehydes and ketones contain an acyl group RC-bonded either to hydrogen or to another carbon

arboxylic acids, compounds of the type RCOH, constitute one of the most fre- quently encountered classes of organic compounds Countless natural products are carboxylic acids or are derived from them. Some carboxylic acids, such as acetic acid, have been known for centuries. Others, such as the prostaglandins, which are pow erful regulators of numerous biological processes remained unknown until relatively

ou have already had considerable experience with carbanionic compounds and rgani their applications in synthetic organic chemistry. The first was acetylide ion in Chapter 9, followed in Chapter 14 by organometallic compounds-Grignard reagents, for example-that act as sources of negatively polarized carbon. In Chapter 18 you learned that enolate ions-reactive

he value of alkyl halides as starting materials for the preparation of variety of organic functional groups has been stressed many times. In our earlier discussions, we noted that aryl halides are normally much less reactive than alkyl halides in reactions that involve carbon-halogen bond cleavage. In the present chapter you will see that aryl halides can exhibit their own patterns of chemical reactivity, and that these reac

he major classes of organic compounds common to living systems are lipids, pro- teins, nucleic acids, and carbohydrates. Carbohydrates are very familiar to us- we call many of them\sugars.\ They make up a substantial portion of the food we eat and provide most of the energy that keeps the human engine running. Carbohy- drates are structural components of the walls of plant cells and the wood of trees. Genetic

he relationship between structure and function reaches its ultimate expression in the chemistry of amino acids, peptides, and protein Amino acids are carboxylic acids that contain an amine function. Under cer- tain conditions the amine group of one molecule and the carboxyl group of a second can react, uniting the two amino acids by an amide bond. Amide(peptide)bond

Absolute configuration(Section 7.5): The three-dimensional Activating substituent (Sections 12.10 and 12.12): A group rrangement of atoms or groups at a stereogenic center. that when present in place of a hydrogen causes a particular Acetal(Section 17.8): Product of the reaction of an aldehyde or reaction to occur faster. Term is most often applied to a ketone with two moles of an alcohol according to the substituents that increase the rate of electrophilic aromatic