15597.eh16.291-30311/3/0510:02Page291 EQA 16 Electrophilic Attack on Derivatives of Benzene: Substituents Control Regioselectivity s on the characteristics. Outline of the Chapter 16-1 Activation or Deactivation by Substituents on the Benzene Ring 16-2 Directing Inductive Effects of Alkyl Groups 16-3 Effects of Substituents in Conjugation with the Benzene Ring 16-4 Electrophilic Attack on Disubstituted Benzenes Effects of substituents on the reactivity and regioselectivity of further electrophilic substitution ona benzene ring. 16-5 Synthetic Strategies General principles and useful new reactions. 16-6 16-7 Polycyclic Aromatic Hydrocarbons and Cancer Keys to the Chapter3 16-1 through 16-3.Directing Effects:Activation and Deactivation Don't forget the basics:Electrophiles seek electrons!So.reactivity of a benzene ring toward electrophiles that dona t which sub h I 39,16 Electrophilic Attack on Derivatives of Benzene: Substituents Control Regioselectivity The preceding chapter introduced you to the properties and chemistry of benzene itself. In this chapter the chemistry is expanded to include several new reactions not only of benzene but also of derivatives of benzene containing various substituents. The text focuses on the effects of substituents on the chemistry of the benzene ring. The first and rate-determining step of electrophilic substitution is the formation of a delocalized cation. Different types of substituents can affect the stability of this cation and make its formation easier or harder. Substituents on the ring also direct the attack of an electrophile to specific positions. This study guide chapter contains information that may help you avoid a lot of memorization. You will see that the effect of a substituent on benzene chemistry can be predicted from a relatively straightforward examination of its electronic characteristics. Outline of the Chapter 16-1 Activation or Deactivation by Substituents on the Benzene Ring 16-2 Directing Inductive Effects of Alkyl Groups 16-3 Effects of Substituents in Conjugation with the Benzene Ring 16-4 Electrophilic Attack on Disubstituted Benzenes Effects of substituents on the reactivity and regioselectivity of further electrophilic substitution on a benzene ring. 16-5 Synthetic Strategies General principles and useful new reactions. 16-6 Reactivity of Polycyclic Benzenoid Aromatics What happens when two or more benzene rings are fused together. 16-7 Polycyclic Aromatic Hydrocarbons and Cancer Keys to the Chapter3 16-1 through 16-3. Directing Effects: Activation and Deactivation Don’t forget the basics: Electrophiles seek electrons! So, reactivity of a benzene ring toward electrophiles will be enhanced by substituents that donate electron density to the ring, and it will be reduced by substituents that withdraw electron density from the ring. “Reactivity” in this context is the rate at which substitution occurs, which is determined by the rate-determining step—electrophilic attack to form a carbocation. Electron-donating 291 1559T_ch16_291-303 11/3/05 10:02 Page 291