Emde mining

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Emde degradation is a name reaction of organic chemistry and was discovered in 1906 by the chemist Hermann Emde (1880–1935). In this reaction, quaternary ammonium salts are split reductively to give tertiary amines and hydrocarbons ( alkanes or alkenes ). It is a modification of the Hofmann mining and is therefore also called the Hofmann-Emde mining .

Overview reaction

The discovery of the Emde degradation took place with the transfer of the hydrogenation reaction of cinnamic acid to 3-phenylpropionic acid in the presence of sodium amalgam on amines. For this purpose, Emde hydrogenated the cinnamyl trimethylammonium chloride 1 with sodium amalgam and received an unexpected result. The hydrogen was not deposited on the C = C double bond of the starting material, but cleaved it on the carbon-nitrogen bond, with trimethylamine 2 , 1-propenylbenzene 3 and hydrochloric acid being formed.

Overview reaction

Emde later found out that the Emde degradation can proceed more gently catalytically with palladium or platinum . Further investigations showed that this degradation reaction does not take place with ammonium salts with four saturated alkyl groups. Only by using sodium in liquid ammonia or dioxane can the Emde breakdown with such salts finally take place.

mechanism

Since there is still too little reliable knowledge of the mechanism of the Emde degradation, there are only tendencies how this could look. It depends on whether an alkane or an alkene is formed as one of the reaction products. When using sodium amalgam, alkenes are formed and when sodium is used in liquid ammonia, alkanes are formed via radical intermediate stages.

use

Chemical degradation reactions such as the Emde degradation serve to clarify the structure of alkaloids . By identifying degradation products, conclusions can be drawn about the alkaloid present. Emde degradation can be used especially for molecules in which Hofmann degradation is not possible, such as 1,2,3,4-tetrahydrodimethylquinolinium chloride . This creates the γ- dimethylaminopropylbenzene:

Usage example

See also

Web links

Individual evidence

  1. ↑ E. Grovenstein, Jr., EP Blanchchard, Jr., DA Gorden, RW Stevenson: Carbanions. II. Cleavage of Tetraalkylammonium Halides by Sodium in Dioxane . In: J. Am. Chem. Soc. tape 81 , 1959, pp. 4842-4850 , doi : 10.1021 / ja01527a023 .
  2. ^ Zerong Wang: Comprehensive Organic Name Reactions and Reagents . John Wiley & Sons, 2009, ISBN 978-0-471-70450-8 , pp. 989-991 .
  3. ↑ H. Emde: About styrylamine bases and their relationship to ephedrine and pseudoephedrine . In: Archives of Pharmacy . tape 244 , 1906, pp. 269-299 , doi : 10.1002 / ardp.19062440405 .
  4. ↑ H. Emde, H. Kull: Degradation of quaternary ammonium compounds with sodium amalgam, an overview . In: Archives of Pharmacy . tape 272 , 1934, pp. 469-481 , doi : 10.1002 / ardp.19342721029 .
  5. ^ Organic Name Reactions . Merck, S. 145 .
  6. ↑ Michael B. Smith: March's Advanced Organic Chemistry , John Wiley & Sons, 7th Edition, 2013, p. 1548, ISBN 978-0-470-46259-1 .
  7. ↑ H. Krauch, W. Kunz, E. Nonnenmacher: Reactions of organic chemistry . WILEY-VCH Verlag, 1997, ISBN 978-3-527-29713-9 , pp. 3 .
  8. ^ Zerong Wang: Comprehensive Organic Name Reactions and Reagents . John Wiley & Sons, 2009, ISBN 978-0-471-70450-8 , pp. 989-991 .
  9. ↑ E. Breitmaier: Alkaloids . Vieweg & Teunber, 2008, ISBN 978-3-8348-0531-7 , pp. 7-8 .
  10. ↑ Gurdeep Raj, Mathu Chhatwal: Organic Name Reactions and Molecular Rearrangements . KRISHNA Prakashan Media, 2008, ISBN 81-87224-25-8 , pp. 145 .