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Schiff bases are common enzymatic intermediates where an amine, such as the terminal group of a lysine residue, reversibly reacts with an aldehyde or ketone of a cofactor or substrate. The common enzyme cofactor pyridoxal phosphate (PLP) forms a Schiff base with a lysine residue and is transaldiminated to the substrate(s). [7]
The structure of the fuchsin dye. The Schiff test is an early organic chemistry named reaction developed by Hugo Schiff, [1] and is a relatively general chemical test for detection of many organic aldehydes that has also found use in the staining of biological tissues. [2]
The Schiff base is an electrophile which reacts in a second step in an electrophilic addition with an enol formed from a carbonyl compound containing an acidic alpha-proton. The Mannich reaction is a condensation reaction. [4]: 140 In the Mannich reaction, primary or secondary amines or ammonia react with formaldehyde to form a Schiff base ...
Conversion of the primary amine to an imine (Schiff base) using an aldehyde. [3] Alkylation of the imine using an alkyl halide, forming an iminium ion. [4] Hydrolysis of the iminium, releasing the secondary amine and regenerating the aldehyde. [5] Because the actual alkylation occurs on the imine, over-alkylation is not possible.
In Schiff base, amine based monomers and aldehyde containing monomers undergo a reaction to create the repeat unit for CMPs. [citation needed] Schiff base is a preferred metal free method due to industrial scale cheap monomers containing multiple aldehyde functional groups. Another benefit of Schiff base is nitrogen is produced in creating CMPs ...
The reaction is thought to begin with the formation of a Schiff base, and then proceed via an intra-molecular condensation to make an imine intermediate (see below). There is then a loss of water that leads to a ring closing and formation of the quinoline derivative.
Imines are related to ketones and aldehydes by replacement of the oxygen with an NR group. When R = H, the compound is a primary imine, when R is hydrocarbyl, the compound is a secondary imine. If this group is not a hydrogen atom, then the compound can sometimes be referred to as a Schiff base. [9]
Crystallography shows that the enzyme is a Class I aldolase, so the mechanism proceeds via the formation of a Schiff base with Lys 167 at the active site. A nearby residue, Lys 201, is critical to reaction by increasing the acidity of protonated Lys 167, so Schiff base formation can occur more readily. [2]