CHAPTER TWENTY-THREE Aryl Halides CH2O OCH orally administered antifungal agent H3O B a dye known as Tyrian purple, which is isolated from a species of Mediterranean for its vivid color HO O OH CNH Chlortetracycline. an antibiotic OH Cl HO CH3 N(CH3h CHa o CH3 CH3O O、CH3CH3 Maytansine: a potent antitumor agent isolated from a bush native to Kenya; HO CHO H FIGURE 23. 1 Some naturally occurring aryl halides The mechanism of this read 1NaOH.H2O.370° tion is discussed in Section 23.8. Chlorobenzene Phenol (97%o) reactions. The carbon-halogen bonds of aryl halides are too strong, and aryl cations are too high in energy, to permit aryl halides to ionize readily in SNl-type processes. Fur thermore, as Figure 23.2 depicts, the optimal transition-state geometry required for SN2 processes cannot be achieved. Nucleophilic attack from the side opposite the nd is blocked by the Back Forward Main MenuToc Study Guide ToC Student o MHHE WebsiteAryl halides are much less reactive than alkyl halides in nucleophilic substitution reactions. The carbon–halogen bonds of aryl halides are too strong, and aryl cations are too high in energy, to permit aryl halides to ionize readily in SN1-type processes. Fur￾thermore, as Figure 23.2 depicts, the optimal transition-state geometry required for SN2 processes cannot be achieved. Nucleophilic attack from the side opposite the carbon–halogen bond is blocked by the aromatic ring. Cl Chlorobenzene OH Phenol (97%) 1. NaOH, H2O, 370°C 2. H 920 CHAPTER TWENTY-THREE Aryl Halides N Cl Cl O Griseofulvin: biosynthetic product of a particular microorganism, used as an orally administered antifungal agent. O H O Br O Dibromoindigo: principal constituent of a dye known as Tyrian purple, which is isolated from a species of Mediterranean sea snail and was much prized by the ancients for its vivid color. H N N H N H O Br O OH CNH2 CH3 O N(CH3)2 O Chlortetracycline: an antibiotic. O O O O O O N O Maytansine: a potent antitumor agent isolated from a bush native to Kenya; 10 tons of plant yielded 6 g of maytansine. CH3O CH3O CH3O CH3O OCH3 H3C HO HO HO OH OH Cl CH3 CH3 CH3 CH3 CH3 CH3 CH3 The mechanism of this reac￾tion is discussed in Section 23.8. FIGURE 23.1 Some naturally occurring aryl halides. Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website