Azines are a functional class of organic compound

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...

s, formed from the condensation reaction

Condensation reaction

A condensation reaction is a chemical reaction in which two molecules or moieties combine to form one single molecule, together with the loss of a small molecule. When this small molecule is water, it is known as a dehydration reaction; other possible small molecules lost are hydrogen chloride,...

 of two equivalent

Equivalent (chemistry)

The equivalent , sometimes termed the molar equivalent, is a unit of amount of substance used in chemistry and the biological sciences.The equivalent is formally defined as the amount of a substance which will either:...

s of an aldehyde

Aldehyde

An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group....

 or ketone

Ketone

In organic chemistry, a ketone is an organic compound with the structure RCR', where R and R' can be a variety of atoms and groups of atoms. It features a carbonyl group bonded to two other carbon atoms. Many ketones are known and many are of great importance in industry and in biology...

 with one equivalent of hydrazine

Hydrazine

Hydrazine is an inorganic compound with the formula N2H4. It is a colourless flammable liquid with an ammonia-like odor. Hydrazine is highly toxic and dangerously unstable unless handled in solution. Approximately 260,000 tons are manufactured annually...

. They may be further classified as aldazines or ketazines, depending on the nature of the carbonyl compound.

Preparation

Azines may be prepared by the direct reaction of a carbonyl compound with hydrazine hydrate: the reaction is exothermic. The usual method of industrial production is the Pechiney-Ugine-Kuhlmann process, starting from the ketone, ammonia

Ammonia

Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

 and hydrogen peroxide

Hydrogen peroxide

Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...

.

Reactions and uses

Azines have been used as precursors to hydrazone

Hydrazone

Hydrazones are a class of organic compounds with the structure R1R2C=NNH2. They are related to ketones and aldehydes by the replacement of the oxygen with the NNH2 functional group...

s and diazo compounds.
Azines are also important intermediates in the industrial production of hydrazine hydrate by the Bayer hydrazine process or the Pechiney-Ugine-Kuhlmann process. They have been also used as sources of hydrazine produced in situ, for example in the production of herbicide

Herbicide

Herbicides, also commonly known as weedkillers, are pesticides used to kill unwanted plants. Selective herbicides kill specific targets while leaving the desired crop relatively unharmed. Some of these act by interfering with the growth of the weed and are often synthetic "imitations" of plant...

 precursor 1,2,4-triazole

1,2,4-Triazole

1,2,4-Triazole is one of a pair of isomeric chemical compounds with molecular formula C2H3N3, called triazoles, which have a five-membered ring of two carbon atoms and three nitrogen atoms. 1,2,4-Triazole is a basic aromatic heterocycle...

.

The coordination chemistry of azines (as ligand

Ligand

In coordination chemistry, a ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. The bonding between metal and ligand generally involves formal donation of one or more of the ligand's electron pairs. The nature of metal-ligand bonding can range from...

s) has also been studied. Acetone

Acetone

Acetone is the organic compound with the formula 2CO, a colorless, mobile, flammable liquid, the simplest example of the ketones.Acetone is miscible with water and serves as an important solvent in its own right, typically as the solvent of choice for cleaning purposes in the laboratory...

 is used to derivatize hydrazine, through formation of acetone azine, for analysis by gas chromatography: the method has been used to determine trace levels of hydrazine in drinking water and pharmaceuticals.

Nomenclature

Azines may be named by substitutive or functional class nomenclature. In functional class nomenclature, the functional modifier "azine" is appended to the name of the carbonyl compound: hence, "acetone azine". In older nomenclature, the functional class name "ketazine" has been used with the names of the hydrocarbyl substituents: e.g., "methyl ethyl ketazine". In substitutive nomenclature, azines are named as derivatives of hydrazine: hence, "diisopropylidenehydrazine". In the presence of groups of higher seniority, the prefixes "hydrazinylidene" and "hydrazinediylidene" are used.

Unsymmetrical azines, that is compounds of the type X=N–N=Y with X ≠ Y, are not named as azines: in the absence of other functional groups having higher seniority, they can be named as substituted hydrazone

Hydrazone

Hydrazones are a class of organic compounds with the structure R1R2C=NNH2. They are related to ketones and aldehydes by the replacement of the oxygen with the NNH2 functional group...

s.