Zincke-Suhl reaction
The Zincke-Suhl reaction is a name reaction from the field of organic chemistry and was first observed in 1906 by Theodor Zincke (1843–1928) and R. Suhl. A reaction of p -cresol to 4-trichloromethyl-4-methylcyclohexa-2,5-dienone takes place. The Zincke-Suhl reaction is a special case of Friedel-Crafts alkylation with aluminum chloride as the active reactant .
Overview reaction
The Zincke-Suhl reaction is carried out with aluminum chloride in tetrachloromethane .
The proton shown in gray is split off during the reaction and the trichloromethyl group marked blue is introduced. 3,4,5-trimethylphenol or 3,4-dimethylphenol can be used as the starting material ; the methyl group substituted in the para position is added .
Possible mechanism
The following mechanism of the Zincke-Suhl reaction is explained using the example of 3,4-dimethylphenol:
As a Lewis acid, the aluminum chloride enters into a coordinate bond with the oxygen atom of 3,4-dimethylphenol ( 1 ), which deprotonates on the alcohol group and thus reacts to form intermediate 2 . A chloride ion is released from the aluminum chloride and hydrogen chloride is released as a gas. At the same time, a coordinative bond is formed between aluminum chloride and carbon tetrachloride, which activates the carbon tetrachloride, which now attacks intermediate 2 in the para position, so that cation 3 and the aluminum tetrachloride ion are formed. The end product 4-trichloromethyl-4-methylcyclohexa-2,5-dienone ( 4 ) is formed by renewed coordination of the aluminum tetrachloride ion to cation 3 and subsequent cleavage with carbon tetrachloride and hydrolysis of aluminum chloride .
literature
- Zerong Wang: Comprehensive Organic Name Reactions and Reagents. 1st edition. John Wiley & Sons, New Jersey 2009, ISBN 978-0-471-70450-8 , pp. 3178-3182.
- Martha Windholz: The Merck Index. 9th edition. MERCK & CO., New Jersey 1976, ISBN 0-911910-26-3 , p. 98.