Von Richter reaction

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The Von Richter reaction , also called the Von Richter rearrangement , is a name reaction in organic chemistry . The reaction was first described by Victor von Richter (1841-1891) in 1871. It is the synthesis of aromatic acids starting from a nitrobenzene derivative .

Overview reaction

A nucleophilic aromatic substitution takes place. The reaction is shown here schematically using the example of the conversion of p - bromonitrobenzene to m - bromobenzoic acid :

Overview reaction of the Von Richter reaction

Instead of bromine, chlorine could also serve as a substituent. During the reaction, the aromatic is made to react with potassium cyanide in an aqueous or alcoholic solution. The product obtained is a carboxy group in the ortho position to the previous nitro group, which is no longer present after the reaction . In the reaction, only very low yields of less than 20% are usually achieved.

Reaction mechanism

The reaction mechanism of the Von Richter reaction is initially similar to that of the Michael addition . Instead of 4-bromonitrobenzene , 4-chloronitrobenzene can also serve as starting material.

Mechanism of the Von Richter Reaction

First, the cyanide attacks in the ortho position to the nitro group in 1 , and 2 is formed . In the next step, the negatively charged oxygen atom attacks the neighboring carbon atom and the five-membered intermediate stage 3 is formed with rearomatization via an intermediate stage . The five-membered ring opens to form a carbonyl group in 4 . The next step is again a five-member formation, the result is 5 . In this five-membered ring is formed after elimination of water , a double bond between the two nitrogen -atoms, so resulting 6 . Then nitrogen is split off and the ring opens to form the carboxylate 7 . Finally, 7 is still protonated to form 3-halobenzoic acid [here: 3-bromobenzoic acid (8) ].

application

The application of the Von Richter reaction is very limited. It is mostly only used in organic syntheses.

history

Victor von Richter recognized that the substitution of the carboxylic acid function takes place in the ortho -position to the formerly present nitro group and postulated a course of the reaction with the formation of an addition product of the aromatic with hydrogen cyanide , which after elimination of nitrous acid initially yields a substituted benzonitrile . This should hydrolyze in water to the corresponding benzoic acid. However, the benzonitrile intermediate could not be detected.

Mechanism of V. von Richter


JF Bunnett conducted extensive research on the Von Richter reaction in the 1950s. To explain the lack of the benzonitrile intermediate, he developed a reaction mechanism in 1958 that proceeds via cyclic intermediates. As the last step, benzoic acid should be formed from an acyl nitrite with elimination of nitrous acid.

Mechanism by JF Bunnett

In 1960, M. Rosenblum discovered that the by-products ammonia and nitrous acid were undetectable and that nitrogen was produced instead .

Mechanism by Rosenbluhm

However, all nitrogen has been further converted to ammonia .

Individual evidence

  1. ^ A b V. von Richter: Investigations on the constitution of benzene derivatives. In: Reports of the German Chemical Society . 4 (1871), pp. 459-468, doi : 10.1002 / cber.187100401154 .
  2. ^ A b c M. Smith, MB Smith, J. March: March's advanced organic chemistry: reactions, mechanisms, and structure. 6th edition. Wiley, 2007, ISBN 978-0-471-72091-1 .
  3. ^ A b R. AY Jones: Physical and Mechanistic Organic Chemistry. (Cambridge Texts in Chemistry and Biochemistry). 1979.
  4. ↑ a b c Zerong Wang: Comprehensive Organic Name Reactions and Reagents . John Wiley & Sons, New Jersey 2009, ISBN 978-0-471-70450-8 , pp. 2911-2914 .
  5. ^ JF Bunnett, JF Cormack, FC McKay: The von Richter Reaction. In: J. Org. Chem. 15 (1950), pp. 481-490, doi : 10.1021 / jo01149a007 .
  6. ^ JF Bunnett, MM Rauhut, D. Knutson, G. E Bussell .: Studies on the Conditions, Scope and Mechanism of the von Richter Reaction. In: J. Am. Chem. Soc. 76 (1954), pp. 5755-5761, doi : 10.1021 / ja01651a039 .
  7. ^ JF Bunnett, MM Rauhut: The von Richter Reaction. III. Substituent Effects. In: J. Org. Chem. 21 (1956), pp. 934-938, doi : 10.1021 / jo01115a004 .
  8. ↑ JF Bunnett: Mechanism and reactivity in aromatic nucleophilic substitution reactions. In: Q. Rev. Chem. Soc. 12 (1958), pp. 1-16, doi : 10.1039 / QR9581200001 .
  9. ↑ M. Rosenblum: The Mechanism of the von Richter Reaction. In: J. Am. Chem. Soc. 82 (1960), pp. 3796-3798, doi : 10.1021 / ja01499a090 .
  10. ↑ J. March: Advanced Organic Chemisytry . John Wiley & Sons, Rakway 1985, ISBN 0-471-88841-9 , pp. 603-604 .

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