Pyridine
[CAS# 110-86-1]

Identification

• Classification: Flavors and spices >> Synthetic spice >> Lactone and oxygen-containing heterocyclic compound >> Thiazole, thiophene and pyridine
• Name: Pyridine
• Synonyms: Azabenzene
• Molecular Formula: C₅H₅N
• Molecular Weight: 79.10
• CAS Registry Number: 110-86-1
• EC Number: 203-809-9
• FEMA: 2966
• SMILES: C1=CC=NC=C1

Properties

• Density: 0.978
• Melting point: -42 °C
• Boiling point: 115-116 °C
• Refractive index: 1.5085-1.5105
• Flash point: 17 °C
• Water solubility: Miscible

Safety Data

• Hazard Symbols: GHS02;GHS07 Danger
• Risk Statements: H225-H302-H312-H315-H319-H332
• Safety Statements: P210-P233-P240-P241-P242-P243-P261-P264-P264+P265-P270-P271-P280-P301+P317-P302+P352-P303+P361+P353-P304+P340-P305+P351+P338-P317-P321-P330-P332+P317-P337+P317-P362+P364-P370+P378-P403+P235-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Acute toxicity	Acute Tox.	4	H332
Flammable liquids	Flam. Liq.	2	H225
Acute toxicity	Acute Tox.	4	H302
Acute toxicity	Acute Tox.	4	H312
Skin irritation	Skin Irrit.	2	H315
Eye irritation	Eye Irrit.	2	H319
Skin sensitization	Skin Sens.	1B	H317
Serious eye damage	Eye Dam.	1	H318
Eye irritation	Eye Irrit.	2	H320
Acute toxicity	Acute Tox.	3	H311
Acute toxicity	Acute Tox.	3	H301
Eye irritation	Eye Irrit.	2A	H319
Skin corrosion	Skin Corr.	1C	H314
Specific target organ toxicity - repeated exposure	STOT RE	1	H372
Specific target organ toxicity - single exposure	STOT SE	3	H336
Explosives	Expl.	1.1	H201
Acute toxicity	Acute Tox.	2	H330
Specific target organ toxicity - repeated exposure	STOT RE	2	H373
Acute toxicity	Acute Tox.	3	H312
Carcinogenicity	Carc.	2	H351
Specific target organ toxicity - single exposure	STOT SE	1	H370
Acute hazardous to the aquatic environment	Aquatic Acute	1	H400
Reproductive toxicity	Repr.	2	H361

• Transport Information: UN 1282

Discovery and Applications

Pyridine is a heterocyclic organic compound characterized by its six-membered aromatic ring containing one nitrogen atom. With the molecular formula C5H5N, pyridine is a colorless liquid with a distinct, unpleasant odor resembling that of rotten fish. It is highly soluble in water and polar solvents, making it a versatile solvent and reagent in various chemical reactions. The discovery of pyridine dates back to 1849, when the German chemist August Wilhelm von Hofmann first isolated it from coal tar during his research into the products of coal combustion.

Hofmann’s discovery was pivotal, as it not only introduced pyridine to the scientific community but also opened avenues for its application in organic chemistry and industrial processes. The compound was subsequently synthesized in the laboratory, and various derivatives were developed, expanding its utility across multiple fields. Pyridine's unique structure and chemical properties make it a key intermediate in the synthesis of numerous organic compounds.

One of the primary applications of pyridine is as a precursor to the production of agrochemicals, including herbicides, insecticides, and fungicides. Pyridine derivatives play a significant role in the synthesis of important agricultural chemicals, enhancing crop protection and pest management. Compounds such as picloram, a herbicide derived from pyridine, have been extensively used in agricultural practices for their effectiveness in controlling unwanted plant species.

In addition to agriculture, pyridine is widely utilized in the pharmaceutical industry. It serves as a building block for the synthesis of various pharmaceutical compounds, including analgesics, anti-inflammatory agents, and antiviral drugs. The ability to modify the pyridine ring through substitution reactions allows chemists to create a diverse range of active pharmaceutical ingredients. Pyridine-based compounds such as isoniazid and nicotinic acid have been instrumental in treating diseases like tuberculosis and improving overall health.

Pyridine is also employed as a solvent and reagent in organic synthesis. Its polar nature and ability to form coordination complexes with metal ions make it an effective solvent for various chemical reactions. Pyridine is used in the synthesis of dyes, resins, and other fine chemicals, contributing to the development of diverse products in the chemical industry. Furthermore, it serves as a catalyst in reactions such as the synthesis of heterocyclic compounds and as a medium for electrophilic substitutions.

While pyridine has valuable applications, it is essential to consider its toxicity and potential health effects. Exposure to pyridine can lead to irritation of the skin, eyes, and respiratory system. As such, proper safety measures and protocols are critical when handling this compound in industrial and laboratory settings. Regulatory agencies have established guidelines to ensure the safe use of pyridine and its derivatives, balancing the benefits of its applications with potential risks.

In conclusion, pyridine is a significant organic compound with a rich history dating back to the 19th century. Its diverse applications span agriculture, pharmaceuticals, and organic synthesis, making it a valuable resource in various industries. As research continues to explore new derivatives and applications, pyridine is poised to maintain its importance in the field of organic chemistry.

References

1979. Investigations into the skin-irritant properties of resiniferonol ortho esters. Inflammation.
DOI: 10.1007/bf00914184

2004. Vibrational Spectroscopy. Characterization I.
DOI: 10.1007/b94235

1933. Pyrrolderivate. Biochemisches Handlexikon.
DOI: 10.1007/978-3-642-90824-8_2