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Unit 17: Nucleophilic Aromatic Substitution and Other Aromatic Reactions

Two escape routes off an aromatic ring that never touch a carbocation: a stabilized addition intermediate, and a strained triple bond hiding inside the ring.

3 topics · 11 questions

Each topic is a path, not a menu: work down it in order and every question builds on the one above. Click any of them to watch the answer draw itself.

The Addition-Elimination Mechanism of Nucleophilic Aromatic Substitution

  1. How it worksHow does a nucleophile add first to form a stable Meisenheimer intermediate before the leaving group finally departs?
  2. Worked exampleFind the product when 1-fluoro-2,4-dinitrobenzene reacts with hydroxide through nucleophilic aromatic substitution.
  3. Common mistakeWhy doesn't nucleophilic aromatic substitution here proceed through a backside SN2-style attack like it would on an alkyl halide?
  4. Going furtherWhat happens to this reaction's rate when the ring's electron-withdrawing groups move from ortho and para to meta instead?
Your turn1 of 2
1-fluoro-2,4-dinitrobenzene reacts with hydroxide through nucleophilic aromatic substitution. What is the product?

The Benzyne Mechanism

  1. How it worksHow does a strong base rip a proton off the carbon next to the leaving group to generate a strained benzyne triple bond?
  2. Worked exampleFind both possible products when chlorobenzene reacts with sodium amide through a benzyne intermediate.
  3. Common mistakeWhy doesn't the nucleophile in a benzyne mechanism necessarily end up on the same carbon the leaving group departed from?
Your turn1 of 2
Chlorobenzene reacts with sodium amide through a benzyne intermediate. What are the two possible products?

Diazonium Salts and Their Reactions

  1. How it worksHow does nitrous acid convert an aromatic amine into a diazonium salt carrying a great leaving group, nitrogen gas?
  2. Worked exampleFind the product when a diazonium salt made from aniline is treated with copper(I) cyanide in a Sandmeyer reaction.
  3. Going furtherWhat happens to a diazonium salt when it is simply warmed up in water instead of being treated with a copper salt?
  4. Ties togetherHow does converting an amine into a diazonium salt let a chemist install a substituent no direct substitution could ever place?
Your turn1 of 2
A diazonium salt made from aniline is treated with copper(I) cyanide in a Sandmeyer reaction. What is the product?