Lesson39 - Substitution Reactions via Arenediazonium Salts...

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Substitution Reactions via Arenediazonium Salts
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N N H H H H H N N Nu H H H H H Nu H H H H H aryl cation Mechanistic Considerations: Substitution of Arenediazonium Ions Although conveniently thought of as proceeding via nucleophilic capture of the aryl cation via an [A N ] step, evidence suggests that many of these reactions may involve radical chain mechanisms (for example, see: J. Am. Chem. Soc. 72 , 1950 , 3013). [D N ] [A N ] In these reactions the leaving group leaves before the Nu adds (compare to electrophilic aromatic substitution mechanism)
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Mechanism of Diazotization nitrosonium ion OR nitrosyl cation O N O sodium nitrite H –H O N O H nitrous acid H –H O N O H H N O N O –H 2 O NH 2 N H H N O N H N O N H N O H H –H H –H N N O H H –H H –H N N O H H N N –H 2 O [pt] [pt] [E β ] or [D N ] [A N ] or [Ad N ] [pt] [pt] [pt] [pt] [E β ]
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Anilines are Prepared by Reduction of the Nitro Group Anilines are commonly formed by the reduction of the nitro group. The reaction is accomplished by the reagents shown below. Given that the nitro group is easily introduced via electrophilic aromatic substitution, the synthetic sequence: Nitration reduction diazotization substitution is a powerful route to many substituted arenes. NO 2 NH 2 Sn, HCl NO 2 NH 2 Pd/C, H 2
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Benzene as an Electrophile: Nucleophilic Aromatic Substitution This reaction goes by an ___________________ pathway, analogous to nucleophilic acyl substitution (recall that substitution
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Lesson39 - Substitution Reactions via Arenediazonium Salts...

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