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Ullmann Reaction and Gomberg - Bechmann Reaction
The document discusses the Gomberg-Bachmann reaction and the Ullmann reaction. The Gomberg-Bachmann reaction involves the base-promoted radical coupling of an aryl diazonium salt and an arene to form a diaryl compound. The mechanism proceeds through an aryl radical intermediate. The Ullmann reaction involves the copper-catalyzed coupling of two aryl halides to form a biaryl product. It proceeds through oxidative addition and reductive elimination steps involving a copper intermediate. Several examples and applications are provided for both reactions.
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Ullmann Reaction and Gomberg - Bechmann Reaction
- 1. GOMBERG-BACHMANN REACTION AND ULLMANN REACTION GOMBERG-BACHMANNREACTION AND ULLMANN REACTION GOMBERG-BACHMANN REACTION AND ULLMANN REACTION GOMBERG- BACHMANN REACTION AND ULLMANN REACTION GOMBERG-BACHMANN REACTION AND ULLMANN REACTION GOMBERG-BACHMANN REACTION AND ULLMANN REACTION GOMBERG-BACHMANN REACTION AND ULLMANN REACTION GOMBERG-BACHMANN REACTION AND ULLMANN REACTION GOMBERG-BACHMANN REACTION AND ULLMANN REACTION GOMBERG-BACHMANN REACTION AND ULLMANN REACTION GOMBERG-BACHMANN REACTION AND ULLMANN REACTION GOMBERG-BACHMANN REACTION AND ULLMANN REACTION GOMBERG-BACHMANN REACTION AND ULLMANN REACTION Presented By: K. Muthu Kannan II M.Sc.,Chemistry S.B.K.College Aruppukottai-626101
- 2. CONTENTS Introduction Howreaction will undergo Mechanism Exercise problems Applications Introduction How reaction will undergo Mechanism Exercise problems Applications GOMBERG – BECHMANN REACTION ULLMANN REACTION
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- 4. INTRODUCTION The Gomberg-Bachmannreaction (1924), named for Russian-American chemist Moses Gomberg (1866-1947) and the American chemist Werner Emmanuel Bachmann (1901-1951), is an aryl-aryl coupling reaction via a diazonium salt. Generally, it is a radical coupling reaction; these are those reactions in which two fragments are joined together (with the help of a metal catalyst). Cross coupling reaction also possible. Moses Gomberg Werner Emmanuel Bachmann
- 5. HOW REACTION WILLUNDERGO Base promoted radical coupling between an aryl diazonium salt and an arene to form a diaryl compound. The arene compound (here benzene) is reacted with a diazonium salt in the presence of a base to provide the diaryl through an intermediate aryl radical.
- 6. MECHANISM OF GOMBERG– BECHMANN REACTION Diazonium salt derivates is reacted with hydroxide ion and forms diazonium oxide which further react with another diazonium salt and forms a double ring compound. Loss of nitrogen gas is there which dissociates the molecule into two fragments out of which one is in the form of diazonium oxide radical and another one is a radical form of benzene (phenyl radical). After that diazonium oxide radical gets reacted with arene group and forms a biaryl compound. The H radical from the above step gets reacted with diazonium oxide radical which immediately form diazonium oxide.
- 7. GOMBERG – BECHMANNREACTION MECHANISM:
- 8. GOMBERG – BECHMANNREACTION EXAMBLE:
- 9. EXERCISE: 1 GOMBERG –BECHMANN REACTION
- 10. EXERCISE: 2 GOMBERG –BECHMANN REACTION
- 11. EXERCISEE: 3 GOMBERG –BECHMANN REACTION
- 12. EXERCISEE: 4 GOMBERG –BECHMANN REACTION
- 13. APPLICATIONS Coupling reactionsare routinely employed in the preparation of pharmaceutical products. For the production of various natural products, coupling reactions are used. Cross-coupling reactions are used for the preparation of monomers and polymers.
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- 15. INTRODUCTION Fritz Ullmann(1875 - 1939) was a german chemist. They named after themselves the following reactions: the Ullmann reaction, the Ullmann condensation, the Greabe-Ullmann synthesis, the Goldberg reaction and the illustrious Jordan- Ullmann-Goldberg synthesis. The Ullmann reaction or Ullmann coupling is an organic named reaction that involves the coupling of two aryl halides in the presence of copper to yield a biaryl as the product. Fritz Ullmann
- 16. HOW REACTION WILLUNDERGO The Ullmann reaction or Ullmann coupling is undergone by Homocoupling of aryl iodides in the presence of copper or nickel or palladium to yield biaryls. The reaction condition for the Ullmann reaction are quite harsh.
- 17. MECHANISM OF ULLMANNREACTION The exact mechanistic pathway of the Ullmann reaction is not known. Currently the most widely accepted mechanism assumes the formation of aryl copper intermediates. Formation of active copper (I). Formed copper (I) species undergoes further oxidative addition with another aryl halide molecule, linking the two molecules. Copper compound formed by the two aryl halide molecule undergoes reductive elimination, resulting in the formation of a new carbon-carbon bond between the two aryl compounds.
- 18. ULLMANN REACTION MECHANISM: Oxidative Addition Cu(0) OxidativeAddition Cu(0) + Cu(I)I Reductive Elimination + Cu(I)I
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- 25. APPLICATIONS Biphenylenes canbe obtained from 2,2-diiodobiphenyl via the ullmann reaction. This reaction can also be employed for the closure of five-membered rings. An unsymmetrical reaction can also be achieved given that one of the reactants is provided in excess. Chiral reactants can be coupled into a chiral product via this reaction. It used to synthesis of polycyclic hydrocarbons.
- 26. REFERENCES Name reactions- A collection of detailed mechanism and synthetic applications, fifth edition by Jie Jack Li. Strategic applications of named reactions in organic synthesis by Laszlo Kurti and Barbara Czako. Organic chemistry volume one by I.L.Finar. https://en.wikipedia.org/wiki/Gomberg%E2%80 %93Bachmann_reaction#:~:text=The%20Gomb erg%E2%80%93Bachmann%20reaction%2C%2 0named,reaction%20via%20a%20diazonium%2 0salt. https://en.wikipedia.org/wiki/Moses_Gomberg#/ media/File:Gombergm01.jpg https://alchetron.com/Werner-Emmanuel- Bachmann https://www.vedantu.com/question- answer/explain-gomberg-reaction-with- mechanism-class-12-chemistry-cbse- 5fd23e9c7182ee79763f5a4a https://www.vedantu.com/chemistry/coupling- reaction https://en.wikipedia.org/wiki/Ullmann_reaction https://en.wikipedia.org/wiki/Fritz_Ullmann https://www.geni.com/photo/view/60000000239 66131829?album_type=photos_of_me&photo_i d=6000000023966468824 https://byjus.com/chemistry/ullmann-reaction/
Editor's Notes
- #5 The net reaction sequence is the connection of carbon skeletons of both fragments. Thus this reaction sequence is a coupling reaction.(joining of two chemical species)
- #10 Ortho product is 55% only, remaining are para product.
- #11 Fulorine has more –I, hence ortho position(near with fluorine) radical is not stable.
- #12 TFAA – Trifluoroacetic anhydride - SOLVENT F3C-COO-CO-CF3
- #13 Acetone - solvent Sodium acetate – base Cupric salt – metal catalyst
- #23 DMF – dimethylforamide N(CH3)2CHO
- #26 Closure ring – ring closing takes place. Unsymmetrical reaction – exercise 4. takes iodobenene 2mole and biaryl 1mole