A Schiff base, named after Hugo Schiff

Hugo Schiff

Hugo Schiff was a German Chemist. He discovered Schiff bases and other imines, and was responsible for research into aldehydes and had the Schiff test named after him. He also worked in the field of amino acids and the Biuret reagent.Born in Frankfurt am Main, Schiff was a student of Friedrich...

, is a compound with a functional group

Functional group

In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. The same functional group will undergo the same or similar chemical reaction regardless of the size of the molecule it is a part of...

 that contains a carbon

Carbon

Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...

-nitrogen

Nitrogen

Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

 double bond

Double bond

A double bond in chemistry is a chemical bond between two chemical elements involving four bonding electrons instead of the usual two. The most common double bond, that between two carbon atoms, can be found in alkenes. Many types of double bonds between two different elements exist, for example in...

 with the nitrogen atom connected to an aryl

Aryl

In the context of organic molecules, aryl refers to any functional group or substituent derived from an aromatic ring, be it phenyl, naphthyl, thienyl, indolyl, etc....

 or alkyl group, not hydrogen

Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

.
Schiff bases in a broad sense have the general formula R¹R²C=NR³, where R is an organic

Organic compound

An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...

 side chain. In this definition, Schiff base is synonymous with azomethine. Some restrict the term to the secondary aldimine

Aldimine

In organic chemistry, an aldimine is an imine that is an analog of an aldehyde.As such, aldimines have the general formula R–CH=N–R. Aldimines are similar to ketimines, which are analogs of ketones.An important subset of aldimines are the Schiff bases,...

s (azomethines where the carbon is connected to a hydrogen atom), thus with the general formula RCH=NR'.

The chain on the nitrogen makes the Schiff base a stable imine

Imine

An imine is a functional group or chemical compound containing a carbon–nitrogen double bond, with the nitrogen attached to a hydrogen atom or an organic group. If this group is not a hydrogen atom, then the compound is known as a Schiff base...

.