Quinaldine or 2-methylquinoline is an

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The ...

with the formula CH₃C₉H₆N. It is one of the methyl derivatives of the

heterocyclic compound A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different elements as members of its ring(s). Heterocyclic chemistry is the branch of organic chemistry dealing with the synthesis, properties, and ...

quinoline. It is bioactive and is used in the preparation of various dyes. It is a colorless oil but commercial samples can appear colored.

Production and reactions

Quinaldine is recovered from

coal tar Coal tar is a thick dark liquid which is a by-product of the production of coke and coal gas from coal. It is a type of creosote. It has both medical and industrial uses. Medicinally it is a topical medication applied to skin to treat psoriasi ...

. It can be prepared from

aniline Aniline is an organic compound with the formula C6 H5 NH2. Consisting of a phenyl group attached to an amino group, aniline is the simplest aromatic amine In organic chemistry, an aromatic amine is an organic compound consisting of an aroma ...

and

paraldehyde Paraldehyde is the cyclic trimer of acetaldehyde molecules. Formally, it is a derivative of 1,3,5-trioxane, with a methyl group substituted for a hydrogen atom at each carbon. The corresponding tetramer is metaldehyde. A colourless liquid, it ...

via Skraup synthesis or from aniline and crotonaldehyde via Doebner-von Miller variation of the

Skraup reaction The Skraup synthesis is a chemical reaction used to synthesize quinolines. It is named after the Czech chemist Zdenko Hans Skraup (1850-1910). In the archetypal Skraup reaction, aniline is heated with sulfuric acid, glycerol, and an oxidizing agent ...

Hydrogenation Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a Catalysis, catalyst such as nickel, palladium or platinum. The process is commonly employed to redox, reduce or S ...

of quinaldine gives

2-methyltetrahydroquinoline 2-Methyltetrahydroquinoline is one of the methyl-substituted derivatives of tetrahydroquinoline. A colorless oil, it is a chiral compound owing to the presence of the methyl substituent. It is produced by the hydrogenation of quinaldine. It is of ...

. This reduction can be conducted enantioselectively.

Properties

Quinaldine has critical point at 787 K and 4.9 MPa and its

refractive index In optics, the refractive index (or refraction index) of an optical medium is a dimensionless number that gives the indication of the light bending ability of that medium. The refractive index determines how much the path of light is bent, or ...

is 1.8116.

Uses

Quinaldine is used in manufacturing anti-malaria drugs, dyes and food colorants (e.g., Quinoline Yellows,

pinacyanol Pinacyanol is a cyanine dye. It is an organic cation, typically isolated as the chloride or iodide salts. The blue dye is prepared from 2-methylquinoline by quaternization with ethyl chloride or ethyl iodide. Condensation with formaldehyde res ...

). It is the precursor to the pH indicator Quinaldine Red. Quinoline Yellow SS

Quinaldine sulfate is an anaesthetic used in fish transportation. In some Caribbean islands it is used to facilitate the collection of tropical fish from reefs.

References

External links

MSDS at Science Lab

* {{cite EB1911 , wstitle=Quinoline , volume=22 , pages=758–760 Quinolines