Zincke

Zincke can refer to several related concepts, primarily in the field of organic chemistry, named after German chemist Theodor Zincke (1843-1928). These include chemical reactions and compounds.

1. Zincke Reaction:

The Zincke reaction is a chemical reaction involving the ring opening of a pyridine salt upon reaction with a primary amine. Typically, the pyridine ring is activated by a substituent (usually a 2,4-dinitrophenyl group) on the nitrogen atom. The reaction results in the formation of an open-chain compound containing a 1,5-dienyl-2-amino derivative. The initial product can often undergo further reactions, such as cyclizations, depending on the specific amine and reaction conditions.

2. Zincke-Suhl Reaction:

The Zincke-Suhl reaction is a related reaction involving the ring opening of pyridine derivatives with activated chlorobenzenes in the presence of a base and a primary amine. This reaction allows for the introduction of the amine substituent and the cleavage of the pyridine ring.

3. Zincke Aldehyde Synthesis:

While less commonly referred to solely as the "Zincke reaction," Zincke also developed methods for the synthesis of aldehydes, particularly through the reaction of certain aromatic compounds with chloroform and alkali.

4. Zincke Salt:

Zincke salts are typically N-(2,4-dinitrophenyl)pyridinium salts, which are key intermediates in the Zincke reaction. These salts are formed by reacting pyridine with 2,4-dinitrochlorobenzene. The dinitroaryl group attached to the nitrogen activates the pyridine ring, making it susceptible to nucleophilic attack by amines.

In summary, the term "Zincke" in chemistry generally refers to reactions and compounds related to the ring opening of pyridine derivatives, often involving activated pyridinium salts and primary amines, as well as some methods for aldehyde synthesis.