Schiff Base

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Related to Aldimine: Schiff base, Pyridoxal phosphate

Schiff base

[′shif ‚bās]
(organic chemistry)
RR′C=NR″ Any of a class of derivatives of the condensation of aldehydes or ketones with primary amines; colorless crystals, weakly basic; hydrolyzed by water and strong acids to form carbonyl compounds and amines; used as chemical intermediates and perfume bases, in dyes and rubber accelerators, and in liquid crystals for electronics.

Schiff Base

 

any one of a class of organic compounds with the general formula RR′C═NR″, where R and R′ represent hydrogen, an alkyl, or an aryl and R″ is an alkyl or aryl; in the latter case, Schiff bases are also called anils.

Schiff bases are crystalline or oily substances that are insoluble in water and soluble in organic solvents. They are weak bases, forming salts with acids in an anhydrous medium; in aqueous acid solutions they undergo hydrolysis to yield an amine and aldehyde. The majority of Schiff bases are stable in alkaline solutions. Schiff bases undergo hydrogenation to give secondary amines (RR′CH—NHR″) and add on many compounds containing mobile hydrogen, such as (β-dicarbonyl compounds, ketones, and imines. They are produced mainly by the condensation of aldehydes or ketones with primary amines.

The reaction was first completed by H. Schiff in 1864 (hence the name of the compounds). Schiff bases are valuable intermediate products of organic synthesis, for example, in the preparation of secondary amines and various heterocyclic compounds. The Schiff bases known as azomethine dyes are used for dyeing acetate and synthetic fibers; they are also used in color photography to reduce the photosensitivity of photographic emulsions.

References in periodicals archive ?
Hydroamination of alkyne 2 with amine 6 yields the aldimine intermediate 7.
2]), an elongation at break greater than 400%, a tensile set of less than 150%, and a Shore A hardness of 44A to 95A as measured at 68[degrees] F and having a matte finish as measured according to ASTM D 523-89 (1999) with an 85 degree surface gloss less than 15, wherein the polyurethane or polyurea coating composition is selected from the group consisting of a water dispersion of a pre-reacted polyurethane and a polyisocyanate or an isocyanate-terminated prepolymer cured with a curing agent selected from a group consisting of an aldimine, a ketimine, a polyaspartic ester and mixtures thereof and an optional cocuring agent selected from the group consisting of a polyamine, a polyol and mixtures thereof.
High pressure liquid chromatographic separation of the labile aldimine (pre-hemoglobin [A.
aldimines and ketimines) that become active upon reacting with atmospheric moisture and/or formulating with ASP-based secondary diamines.