23.4 Reactions of Aryl Halides: A Review and a Preview TABLE 23.2 Summary of Reactions Discussed in Earlier Chapters That Yield Aryl Halides Reaction(section) and comments General equation and specific example Halogenation of arenes( Section 12.5) Aryl chlorides and bromides are con ArH X2 -> ArX HX niently prepared by electrophilic aro- Arene Halogen Fex, Aryl matic substitution the reaction is I ited to chlorination and bromination Fluorination is difficult to control: iodi nation is too slow to be useful 2 Nitrobenzene Bromine The Sandmeyer reaction(Section 22. 18) 1. NaNO2, HaO Diazotization of a primary arylamine ArNH2 →Arx 2. CUX followed by treatment of the diazo- Primary arylamine Aryl halide nium salt with copper()bromid copper()chloride yields the corre- CI NH2 sponding aryl bromide or aryl chloride 1-Amino-8-chloronaphthalene 1-Bromo-8-chloronaphth. Diazotization of an arylamine followed ArNH, 1. NaNO, H,o arN=N.f/heat The Schiemann reaction(Section 22. 18) ArF by treatment with fluoroboric acid Aryl diazonium gives an aryl diazonium fluoroborate arylami salt. Heating this salt converts it to an aryl fluoride ChS Aniline benzene (51-57%) Reaction of aryl diazonium salts with iodide ion(Section 22. 18)Adding ArNH2 Arl potassium iodide to a solution of an Primary arylamine Aryl iodide aryl diazonium ion leads to the forma- tion of an aryl iodide CsHSNH 23.4 REACTIONS OF ARYL HALIDES: A REVIEW AND A PREVIEW Table 23.3 summarizes the reactions of aryl halides that we have encountered to this Noticeably absent from Table 23.3 are nucleophilic substitutions. We have, to thi point, seen no nucleophilic substitution reactions of aryl halides in this text. Chloroben zene, for example, is essentially inert to aqueous sodium hydroxide at room temperature Reaction temperatures over 300C are required for nucleophilic substitution to proceed at a reasonable rate Back Forward Main MenuToc Study Guide ToC Student o MHHE Website23.4 Reactions of Aryl Halides: A Review and a Preview 919 TABLE 23.2 Summary of Reactions Discussed in Earlier Chapters That Yield Aryl Halides Reaction (section) and comments Halogenation of arenes (Section 12.5) Aryl chlorides and bromides are con￾veniently prepared by electrophilic aro￾matic substitution. The reaction is lim￾ited to chlorination and bromination. Fluorination is difficult to control; iodi￾nation is too slow to be useful. The Sandmeyer reaction (Section 22.18) Diazotization of a primary arylamine followed by treatment of the diazo￾nium salt with copper(I) bromide or copper(I) chloride yields the corre￾sponding aryl bromide or aryl chloride. Reaction of aryl diazonium salts with iodide ion (Section 22.18) Adding potassium iodide to a solution of an aryl diazonium ion leads to the forma￾tion of an aryl iodide. The Schiemann reaction (Section 22.18) Diazotization of an arylamine followed by treatment with fluoroboric acid gives an aryl diazonium fluoroborate salt. Heating this salt converts it to an aryl fluoride. General equation and specific example ArH Arene Halogen X2 Aryl halide ArX Hydrogen halide HX Fe or FeX3 Fe m-Bromonitrobenzene (85%) Br O2N O2N Nitrobenzene Bromine Br2 Primary arylamine ArNH2 Aryl halide ArX 1. NaNO2, H3O 2. CuX Primary arylamine ArNH2 Aryl iodide ArI 1. NaNO2, H3O 2. KI 1-Amino-8-chloronaphthalene Cl NH2 1-Bromo-8-chloronaphthalene (62%) Cl Br 1. NaNO2, HBr 2. CuBr Aryl diazonium fluoroborate BF4  ArNPN Primary arylamine ArNH2 Aryl fluoride ArF 1. NaNO2, H3O heat 2. HBF4 Fluorobenzene (51–57%) C6H5F Aniline C6H5NH2 1. NaNO2, H2O, HCl 2. HBF4 3. heat Iodobenzene (74–76%) C6H5I Aniline C6H5NH2 1. NaNO2, HCl, H2O 2. KI 23.4 REACTIONS OF ARYL HALIDES: A REVIEW AND A PREVIEW Table 23.3 summarizes the reactions of aryl halides that we have encountered to this point. Noticeably absent from Table 23.3 are nucleophilic substitutions. We have, to this point, seen no nucleophilic substitution reactions of aryl halides in this text. Chloroben￾zene, for example, is essentially inert to aqueous sodium hydroxide at room temperature. Reaction temperatures over 300°C are required for nucleophilic substitution to proceed at a reasonable rate. Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website