What Is Quinoline?
Quinoline is an organic compound belonging to the heterocyclic aromatic family. Its chemical formula is C9H7N.
Quinoline has a fused ring structure of a benzene ring and a pyridine ring. It is also known as 1-azanaphthalene, 1-benzazine, benzo[b]pyridine, etc. Its CAS registration number is 91-22-5.
It has a molecular weight of 129.16, a melting point of -15°C, and a boiling point of 238°C. At room temperature, it is a colorless, hygroscopic liquid substance. It has a strong odor. Its density is 1.09 g/mL and the pKa of the conjugated acid is 4.85.
Although only slightly soluble in water, it is extremely soluble in ethanol and diethyl ether. In natural products, it is found in coal tar.
Uses of Quinoline
The main uses of quinoline are as a synthetic raw material for dyes, agrochemicals, pharmaceuticals, and polymers, as a reagent for the determination of metal ions, and as a solvent.
Quinoline has the property of forming salts with specific metal ions such as Fe3+ and Zn2+ in solution. This property makes it possible to use quinoline as a reagent for quantitative determination of metal ions.
Quinoline is also used as a raw material for pharmaceutical synthesis in the preparation of niacin, 8-hydroxyquinoline, quinine, and others. In addition, quinoline is used in a variety of other fields, such as in the production of quinoline dyes, as a preservative, and as a disinfectant.
Properties of Quinoline
1. Synthesis of Quinoline
Several synthetic routes have been reported for quinolines, including the Combes quinoline synthesis, in which an imine is prepared from aniline and a 1,3-diketone, followed by cyclization of the product intermediate with an acid. The Conrad-Limpach synthesis is a condensation of anilines with β-ketoesters.
Skraup synthesis is another well-known synthetic method, in which anilines are synthesized from glycerol and nitrobenzene in the presence of sulfuric acid.
Glycerin Is Dehydrated By Acid To Form Acrolein.
The aza-Michael addition of aniline to the acrolein to form β-aminoaldehyde. The Intramolecular Friedel-Crafts reaction proceeds to the carbonyl group. Dehydration of the intermediate leads to the formation of 1,2-dihydroquinoline, and dehydrogenation occurs with nitrobenzene acting as an oxidant
2. Chemical Properties of Quinoline
Quinoline is a substance that can be altered by light. If stored for a long period of time in an area exposed to light, quinoline will turn yellow, and if left unattended, will turn brown.
When storing, avoid high temperatures, direct sunlight, heat, flames, and static sparks. Mixture with strong oxidizers should also be avoided. Hazardous decomposition products include carbon monoxide, carbon dioxide, and nitrogen oxides.
Types of Quinolines
Quinoline is sold primarily as a reagent product for research and development. The types of volumes include 1mL, 25mL, 500mL, 3L, and 25g. It is offered in volumes that are easy to use in the laboratory. These reagent products can be stored at room temperature.
It is a chemical used as a solvent as well as a raw material for organic synthesis and for the quantitative determination of metal ions as mentioned above.
Other Information on Quinoline
Quinoline Toxicity Information
Quinoline is a toxic substance. Specific hazards include skin irritation, strong eye irritation, suspected hereditary disease, carcinogenesis, and respiratory tract irritation.