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Chemical Structure History Chemical properties Productions Uses Toxicity information Hazards References
Pyridine structure
Chemical Name:
AA;PY;PYR;cp32;Azine;Piridina;Pirydyna;PYRIDINE;FEMA 2966;FEMA 2932
Molecular Formula:
Formula Weight:
MOL File:

Pyridine Properties

Melting point:
-42 °C
Boiling point:
96-98 °C(lit.)
0.983 g/mL at 20 °C
vapor density 
2.72 (vs air)
vapor pressure 
23.8 mm Hg ( 25 °C)
refractive index 
n20/D 1.509(lit.)
Flash point:
68 °F
storage temp. 
Store at RT.
H2O: in accordance
5.25(at 25℃)
Nauseating odor detectable at 0.23 to 1.9 ppm (mean = 0.66 ppm)
Relative polarity
8.81 (H2O, 20℃)
explosive limit
Water Solubility 
λ: 305 nm Amax: 1.00
λ: 315 nm Amax: 0.15
λ: 335 nm Amax: 0.02
λ: 350-400 nm Amax: 0.01
Exposure limits
TLV-TWA 5 ppm (~15 mg/m3) (ACGIH, MSHA,and OSHA); STEL 10 ppm (ACGIH), IDLH 3600 ppm (NIOSH).
Stable. Flammable. Incompatible with strong oxidizing agents, strong acids.
CAS DataBase Reference
110-86-1(CAS DataBase Reference)
NIST Chemistry Reference
EPA Substance Registry System
  • Risk and Safety Statements
  • Hazard and Precautionary Statements (GHS)
  • NFPA
Hazard Codes  T,N,F,Xn
Risk Statements  11-20/21/22-39/23/24/25-23/24/25-52-36/38
Safety Statements  36/37/39-38-45-61-28A-26-28-24/25-22-36/37-16-7
RIDADR  UN 1282 3/PG 2
WGK Germany  2
RTECS  UR8400000
Autoignition Temperature 482 °C
Hazard Note  Highly Flammable/Harmful
HS Code  2933 31 00
HazardClass  3
PackingGroup  II
Hazardous Substances Data 110-86-1(Hazardous Substances Data)
Toxicity LD50 orally in rats: 1.58 g/kg (Smyth)
Signal word: Danger
Hazard statements:
Code Hazard statements Hazard class Category Signal word Pictogram P-Codes
H225 Highly Flammable liquid and vapour Flammable liquids Category 2 Danger P210,P233, P240, P241, P242, P243,P280, P303+ P361+P353, P370+P378,P403+P235, P501
H301 Toxic if swalloed Acute toxicity,oral Category 3 Danger P264, P270, P301+P310, P321, P330,P405, P501
H302 Harmful if swallowed Acute toxicity,oral Category 4 Warning P264, P270, P301+P312, P330, P501
H311 Toxic in contact with skin Acute toxicity,dermal Category 3 Danger P280, P302+P352, P312, P322, P361,P363, P405, P501
H312 Harmful in contact with skin Acute toxicity,dermal Category 4 Warning P280,P302+P352, P312, P322, P363,P501
H315 Causes skin irritation Skin corrosion/irritation Category 2 Warning P264, P280, P302+P352, P321,P332+P313, P362
H319 Causes serious eye irritation Serious eye damage/eye irritation Category 2A Warning P264, P280, P305+P351+P338,P337+P313P
H331 Toxic if inhaled Acute toxicity,inhalation Category 3 Danger P261, P271, P304+P340, P311, P321,P403+P233, P405, P501
H332 Harmful if inhaled Acute toxicity,inhalation Category 4 Warning P261, P271, P304+P340, P312
H370 Causes damage to organs Specific target organ toxicity, single exposure Category 1 Danger P260, P264, P270, P307+P311, P321,P405, P501
Precautionary statements:
P210 Keep away from heat/sparks/open flames/hot surfaces. — No smoking.
P260 Do not breathe dust/fume/gas/mist/vapours/spray.
P261 Avoid breathing dust/fume/gas/mist/vapours/spray.
P280 Wear protective gloves/protective clothing/eye protection/face protection.
P311 Call a POISON CENTER or doctor/physician.
P301+P310 IF SWALLOWED: Immediately call a POISON CENTER or doctor/physician.
P303+P361+P353 IF ON SKIN (or hair): Remove/Take off Immediately all contaminated clothing. Rinse SKIN with water/shower.
P304+P340 IF INHALED: Remove victim to fresh air and Keep at rest in a position comfortable for breathing.
P305+P351+P338 IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continuerinsing.
P337+P313 IF eye irritation persists: Get medical advice/attention.
P370+P378 In case of fire: Use … for extinction.
P403+P235 Store in a well-ventilated place. Keep cool.

NFPA 704

Diamond Hazard Value Description
3 0
Health   3 Short exposure could cause serious temporary or moderate residual injury (e.g. liquid hydrogen, sulfuric acid, calcium hypochlorite, hexafluorosilicic acid)
Flammability   3 Liquids and solids (including finely divided suspended solids) that can be ignited under almost all ambient temperature conditions . Liquids having a flash point below 22.8 °C (73 °F) and having a boiling point at or above 37.8 °C (100 °F) or having a flash point between 22.8 and 37.8 °C (73 and 100 °F). (e.g. gasoline, acetone)
Instability   0 Normally stable, even under fire exposure conditions, and is not reactive with water (e.g. helium,N2)

(NFPA, 2010)

Pyridine price More Price(68)

Manufacturer Product number Product description CAS number Packaging Price Updated Buy
Sigma-Aldrich 02486 Pyridine analytical standard 110-86-1 1ml $29.1 2018-11-13 Buy
Sigma-Aldrich 1601747 Pyridine United States Pharmacopeia (USP) Reference Standard 110-86-1 3x1.2ml $348 2018-11-13 Buy
Alfa Aesar 019378 Pyridine, ACS, 99.0% min 110-86-1 *4x1L $307 2018-11-16 Buy
Alfa Aesar 019378 Pyridine, ACS, 99.0% min 110-86-1 1L $100 2018-11-16 Buy
Sigma-Aldrich 270970 Pyridine anhydrous, 99.8% 110-86-1 100ml $101 2018-11-13 Buy

Pyridine Chemical Properties,Uses,Production

Chemical Structure

Lewis structureSkeletal formula
Ball-and-stick diagramSpace-filling model
Molecular model kit
Pyridine is a basic heterocyclic organic compound with the chemical formula C5H5N. It is structurally related to benzene, with one methine group (=CH−) replaced by a nitrogen atom. The pyridine ring occurs in many important compounds, including azines and the vitamins niacin and pyridoxine.


Thomas Anderson
Pyridine was discovered in 1849 by the Scottish chemist Thomas Anderson as one of the constituents of bone oil. Two years later, Anderson isolated pure pyridine through fractional distillation of the oil.

Chemical properties

It is a colorless or light yellow, highly flammable, weakly alkaline, water-soluble liquid with a distinctive, unpleasant fish-like smell. Its melting point is -41.6 ℃, and boiling point is 115.2 ?C. It will form azeotropic mixture with water, and boiling point of the mixture is 92~93 ?C. The property is used to purify pyridine in industry.) Its density is 0.9819g / cm3. Pyridine is soluble in water, ethanol, ether and other organic solvents, and itself can also be used as solvent.


2.1 Separation from Tar
Pyridine bases are a constituent of tars. They were isolated from coal tar or coal gas before synthetic manufacturing processes became established. The amounts contained in coal tar and coal gas is small, and the pyridine bases isolated from them are a mixture of many components. Thus, with a few exceptions, isolation of pure pyridine bases was expensive. Today, almost all pyridine bases are produced by synthesis. 2.2 Chichibabin synthesis

Fig. 2-1 Formation of acrolein from acetaldehyde and formaldehyde

Fig. 2-2 Condensation of pyridine from acrolein and acetaldehyde

The Chichibabin pyridine synthesis was reported in 1924 and is still in use in industry. Acetaldehyde and formaldehyde react with ammonia to give mainly pyridine. First, acrolein is formed in a Knoevenagel condensation from the acetaldehyde and formaldehyde. It is then condensed with acetaldehyde and ammonia into dihydropyridine, and then oxidized with a solid-state catalyst to pyridine. The reaction is usually carried out at 350-550°C and a space velocity of 500-1000 h -1 in the presence of a solid acid catalyst (e.g., silica-alumina). The product consists of a mixture of pyridine, simple methylated pyridines (picoline), and lutidine. The recovered pyridine is separated from byproducts in a multistage process.

Fig. 2-3 Flow sheet of pyridine and methylpyridine production from acetaldehyde and formaldehyde with ammonia. A) Reactor; b) Collector; c) Extraction; d) Solvent distillation; e) Distillation

2.3 Dealkylation of Alkylpyridines
Pyridine can be prepared by dealkylation of alkylated pyridines, which are obtained as byproducts in the syntheses of other pyridines. The oxidative dealkylation is carried out either using air over vanadium(V) oxide catalyst, by vapor-dealkylation on nickel-based catalyst, or hydrodealkylation with a silver- or platinum-based catalyst. Yields of pyridine up to be 93% can be achieved with the nickel-based catalyst.

2.4 Synthesis from Nitriles and Acetylene
Liquid-phase reaction of nitriles with acetylene is carried out at 120-180 ?C and 0.8-2.5 MPa in the presence of an organocobalt catalyst and gives 2-substituted pyridines: 

Fig. 2-4 Synthesis of 2-methylpyridine from nitriles and acetylene
The trimerization of a part of a nitrile molecule and two parts of acetylene into pyridine is called Bönnemann cyclization. When using acetonitrile as the nitrile, 2-methylpyridine is obtained, which can be dealkylated to pyridine.

2.5 Synthesis from Acrylonitrile and Ketones

Fig. 2-5 Synthesis of 2-methylpyridine from acrylonitrile and acetone
Synthesis from acrylonitrile and acetone gives 2-methylpyridine selectively, which can be dealkylated to pyridine. First, the reaction of acrylonitrile and acetone, catalyzed by a primary aliphatic amine such as isopropylamine and a weak acid such as benzoic acid, occurs in the liquid phase at 180 ?C and 2.2 MPa to give 5-oxohexanenitrile, with 91% selectivity. The acrylonitrile conversion is 86%. Then cyclization and dehydration of the initial product are carried out in the gas phase in the presence of hydrogen over a palladium, nickel, or cobalt-containing catalyst at 240?C to give 2-methylpyridine in 84% yield.

2.6 Synthesis from Dinitriles
In a vapor-phase reaction over a nickel-containing catalyst in the presence of hydrogen, 2-methylglutaronitrile gives 3-methylpiperidine, which then undergoes dehydrogenation over palladium –alumina to give 3-methylpyridine. And 3-methylpyridine also can be dealkylated to pyridine.

Fig. 2-6 Synthesis of 2-methylpyridine from Dinitriles
A one-step gas-phase reaction over a palladium-containing catalyst is reported to give 3-methylpyridine in 50% yield.

2.7 Biosynthesis
Several pyridine derivatives play important roles in biological systems. While its biosynthesis is not fully understood, nicotinic acid (vitamin B3) occurs in some bacteria, fungi, and mammals. Mammals synthesize nicotinic acid through oxidation of the amino acid tryptophan, where an intermediate product, aniline, creates a pyridine derivative, kynurenine. On the contrary, the bacteria Mycobacterium tuberculosis and Escherichia coli produce nicotinic acid by condensation of glyceraldehyde 3-phosphate and aspartic acid.

2.8 Other methods
Ethylene and ammonia react in the presence of a palladium complex catalyst to give 2-methylpyridine and MEP. Pyridine can be prepared from cyclopentadiene by ammoxidation, or from 2-pentenenitrile by cyclization and dehydrogenation. Furfuryl alcohol or furfural reacts with ammonia in the gas phase to give pyridine. 2-Methylpyridine is also prepared from aniline.


3.1 Solvent
Pyridine is a polar, basic, low-reactive solvent, especially for dehydrochlorination reactions and extraction of antibiotics. In elimination reaction, pyridine acts as the base of the elimination reaction and bonds the resulting hydrogen halide to form a pyridinium salt. In esterifications and acylations, pyridine activates the carboxylic acid halides or anhydrides.

3.2 Medicines
Pyridine's chemical structure can be found in various medications that are synthesized thanks in part to pyridine. One example is a medication called esomeprazole, the generic name for Nexium. This is a medication that's used to treat GERD, or gastroesophageal reflux disease. Another example of a pyridine containing medication is loratadine, more commonly known by its brand name of Claritin. Loratadine helps in the treatment of allergies.

3.3 Pesticides
The main use of pyridine is as a precursor to the herbicides paraquat and diquat. The first synthesis step of insecticide chlorpyrifos consists of the chlorination of pyridine. Pyridine is also the starting compound for the preparation of pyrithione-based fungicides. Cetylpyridinium and laurylpyridinium, which can be produced from pyridine with a Zincke reaction, are used as antiseptic in oral and dental care products. Pyridine is easily attacked by alkylating agents to give N-alkylpyridinium salts. One example is cetylpyridinium chloride.

Fig 3-1 Synthesis of paraquat

3.4 Synthesis of piperidine
Piperidine, a fundamental nitrogen heterocycle, is important synthetic building-block. Piperidines are produced by hydrogenation of pyridine with a nickel-, cobalt-, or ruthenium-based catalyst at elevated temperatures.
C5H5N + 3 H2 → C5H10NH 3.5 Ligand and Lewis base
Pyridine is widely used as a ligand in coordination chemistry. As a ligand of metal complex, it can be easily replaced by a stronger Lewis base, which can be used in the catalysis of polymerization and hydrogenation reactions. After the completion of reaction, pyridine ligand replaced during the reaction can be restored again. Pyridine is also used as a base in condensation reactions. As a base, pyridine can be used as the Karl Fischer reagent, but it is usually replaced by alternatives with a more pleasant odor, such as imidazole.

3.6 Others
Except for above uses, Pyridine is also used to product polycarbonate resins, vitamins, food flavorings, paints, dyes, rubber products, adhesives, and waterproofing for fabrics. Pyridine is added to ethanol to make it unsuitable for drinking. It is also used in the in vitro synthesis of DNA.

Toxicity information

4.1 Toxicity Level
Low Toxicity

4.2 Acute Toxicity
LD501580mg/kg (Large mice, oral); 1121mg/kg (Rabbit, through skin); inhaled by human 25mg/m3×20 min, irritation of conjunctiva and upper respiratory tract mucosa. Subacute and chronic toxicity: inhaled by large mice 32.3mg/m3×7 hours/day x5 days/week x6 months, increase in liver weight; inhaled by humans 20~40mg/m3 (long term), nerve damage, unsteady walking, digital tremors, low blood pressure, over-sweating, occasional liver and kidney damage.


5.1 Health hazards
Pyridine is extremely toxic by ingestion and inhalation. Vapors are heavier than air. its combustion produces toxic oxides of nitrogen. Pyridine is highly flammable (its flash point is just 17 ºC). Pyridine also could have neurotoxic and genotoxic effects.

5.2 Fire Hazards
Behavior in Fire: Vapor is heavier than air and may travel considerable distance to source of ignition and flash back.


  11. Shimizu, S.; Watanabe, N.; Kataoka, T.; Shoji, T.; Abe, N.; Morishita, S.; Ichimura, H. (2005), "Pyridine and Pyridine Derivatives", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a22_399

Chemical Properties

Pyridine is a weak base (pKa= 5.25); a 0.2 M solution has a pH of 8.5 (HSDB 1988). Its carbon atoms are deactivated towards electrophilic substitution. This is especially true in acidic media, where salts form at the nitrogen. It does, however, readily undergo nucleophilic substitution, preferentially at the C-2 and also at the C-4 position (Jori et al 1983). Being a tertiary amine, pyridine reacts with alkylating agents to form quaternary salts (Santodonato et al 1985). Because of its reduced capacity to donate electrons, it is more resistant to oxidation than benzene. Oxidation with peroxy acids forms pyridine N-oxide which is then capable of undergoing electrophilic substitution (Jori et al 1983). Pyridine reacts violently with a number of compounds, including nitric acid, sulfuric acid, maleic anhydride, perchromate, beta-propiolactone and chlorosulfonic acid. Thermal decomposition can liberate cyanides (Gehring 1983). Both the pyridinium ion and pyridine itself are readily reduced to the commercially important compound, piperidine (Jori et al 1983).

Chemical Properties

Pyridine, C5H5N, is a yellowish, flammable, poisonous organic solvent with a very distinctive and penetrating odor. Pyridine is soluble in water, alcohol, benzene, and ether.It has a boiling point of 116°C (240 OF). Pyridine is used in paints,medicine,and textile dyeing.

Chemical Properties

Pyridine is a colorless liquid. Nauseating, sickening fish-like odor. The Odor Threshold is 0.17 ppm.


Pyridine was discovered by Anderson in coal tar in 1846 (Windholz et al 1983). It is found in tobacco smoke (Vohl and Eulenberg 1871; Lehmann 1909) and roasted coffee (Bertrand and Weisweiller 1913). Pyridine is found in wood oil and in the leaves and roots of Atropa belladonna (HSDB 1988), and is also a component of creosote oil (Krone et al 1986).


Used as solvent; complexing agent.


As solvent for Anhydrous mineral salts. Synthetic intermediate in laboratory and industry.


Pyridine is used as a solvent in paint andrubber industries; as an intermediate in dyesand pharmaceuticals; for denaturing alcohol;and as a reagent for cyanide analysis. Itoccurs in coal tar.


An organic liquid of formula C5H5N. The molecules have a hexagonal planar ring and are isoelectronic with benzene. Pyridine is an example of an aromatic heterocyclic compound, with the electrons in the carbon–carbon pi bonds and the lone pair of the nitrogen delocalized over the ring of atoms. The compound is extracted from coal tar and used as a solvent and as a raw material for organic synthesis.


azine: An organic heterocyclic compoundcontaining a six-memberedring formed from carbon and nitrogenatoms. Pyridine is an examplecontaining one nitrogen atom(C5H5N). Diazines have two nitrogenatoms in the ring (e.g. C4H4N2), andisomers exist depending on the relativepositions of the nitrogen atoms.Triazines contain three nitrogenatoms.


pyridine: A colourless liquid with astrong unpleasant smell, C5H5N (seeformula); r.d. 0.98; m.p. –42°C; b.p.115°C. Pyridine is an aromatic heterocycliccompound present in coaltar. It is used in making other organicchemicals.


ChEBI: An azaarene comprising a benzene core in which one -CH group is replaced by a nitrogen atom. It is the parent compound of the class pyridines.

Production Methods

Pyridine is produced from the gases obtained by the coking of coal and by direct synthesis. The light-oil fraction of coal tar is treated with sulfuric acid to produce water-soluble pyridine salts and then the pyridine bases are recovered from the aqueous phase by sodium hydroxide or ammonia (Jori et al 1983). The majority of U.S. production is through synthetic means. This process uses a vapor-phase reaction of acetaldehyde, formaldehyde and ammonia, which yields a mixture of pyridine and 3-methylpyridine (Santodonato et al 1985). The product ratio depends on the relative amounts of acetaldehyde and formaldehyde. Added methanol increases the yield. The U.S. production of pyridine was estimated at 32 to 47 million pounds in 1975 (Reinhardt and Brittelli 1981). Pyridine is commercially available in technical, 2° and 1° grades, the latter two referring to their boiling ranges. Major impurities are higher boiling homologues, such as picolines, lutidines and collidines, which are mono-, di-, and trimethylpyridines (Santodonato et al 1985; Jori et al 1983).

General Description

A clear colorless to light yellow liquid with a penetrating nauseating odor. Density 0.978 g / cm3. Flash point 68°F. Vapors are heavier than air. Toxic by ingestion and inhalation. Combustion produces toxic oxides of nitrogen.

Air & Water Reactions

Highly flammable. Soluble in water.

Reactivity Profile

Azabenzene is a base. Reacts exothermically with acids. During preparation of a complex of Azabenzene with chromium trioxide, an acid, the proportion of chromium trioxide was increased. Heating from this acid-base reaction led to an explosion and fire [MCA Case History 1284 1967]. A 0.1% solution of Azabenzene (or other tertiary amine) in maleic anhydride at 185°C gives an exothermic decomposition with rapid evolution of gas [Chem Eng. News 42(8); 41 1964]. Mixing Azabenzene in equal molar portions with any of the following substances in a closed container caused the temperature and pressure to increase: chlorosulfonic acid, nitric acid (70%), oleum, sulfuric acid (96%), or propiolactone [NFPA 1991]. The combination of iodine, Azabenzene, sulfur trioxide, and formamide developed a gas over pressurization after several months. This arose from the slow formation of sulfuric acid from external water, or from dehydration of the formamide to hydrogen cyanide. Ethylene oxide and SO2 can react violently in Azabenzene solution with pressurization if ethylene oxide is in excess (Nolan, 1983, Case History 51).


Flammable, dangerous fire risk, explosive limits in air 1.8–12.4%. Toxic by ingestion and inhalation. Skin irritant, liver and kidney damage. Questionable carcinogen.

Health Hazard

The acute toxicity of pyridine is low. Inhalation causes irritation of the respiratory system and may affect the central nervous system, causing headache, nausea, vomiting, dizziness, and nervousness. Pyridine irritates the eyes and skin and is readily absorbed, leading to systemic effects. Ingestion of pyridine can result in liver and kidney damage. Pyridine causes olfactory fatigue, and its odor does not provide adequate warning of the presence of harmful concentrations.
Pyridine has not been found to be carcinogenic or to show reproductive or developmental toxicity in humans. Chronic exposure to pyridine can result in damage to the liver, kidneys, and central nervous system.

Health Hazard

Vapor irritates eyes and nose. Liquid irritates skin and is absorbed through the skin. Overexposure causes nausea, headache, nervous symptoms, increased urinary frequency.

Health Hazard

The toxic effects of pyridine are mainly centered on the central nervous system (CNS), gastrointestinal (GI) tract, liver and kidneys. When men were treated orally with 1.8-2.5 ml of pyridine daily for up to two months, in an aborted attempt at Northwestern University to treat epilepsy, they experienced anorexia, nausea, vomiting, gastric distress, headache, fatigue, faintness and depression (Pollock et al 1943). Two cases of liver and kidney damage and one death occurred. Another reported fatality was caused by the accidental swallowing of one-half cup of commercial pyridine. The patient experienced abdominal pain, inability to swallow, lung congestion and bronchitis and died two d later (Helme 1893; Pollock et al 1943). The probable oral lethal dose is 0.5-5.0 g/kg (HSDB 1988) and a LDLo dose for man was 500 mg/kg p.o. (Jori et al 1983). Exposures to doses that are too low to produce overt clinical symptoms can cause hepatic damage and repeated low-level exposures can cause cirrhosis (Gehring 1983). Many of the cases of human poisoning have been due to inhalation of pyridine vapor. The vapor is irritating to mucous surfaces and causes eye and nasal irritation (HSDB 1988). Chronic exposures of 6-13 p.p.m. have caused toxic effects related to both the CNS and GI tract, such as headache, vertigo, nervousness, insomnia, nausea and vomiting. Other symptoms caused by pyridine vapor include abdominal or lower back pain with urinary frequency and nervous system affliction with speech disorders (Reinhardt and Brittelli 1981; HSDB 1988). The maximum long-term exposure is estimated to be 1-5 p.p.m. (Santodonato 1985; Teisinger 1948).

Health Hazard

The toxic effects of pyridine include headache,dizziness, nervousness, nausea, insomnia,frequent urination, and abdominal pain.The symptoms were transient, occurred inpeople from subacute exposure to pyridinevapors at about 125 ppm for 4 hours a dayfor 1–2 weeks (Reinhardt and Brittelli 1981).The target organs to pyridine toxicity are thecentral nervous system, liver, kidneys, gastrointestinaltract, and skin.
The routes ofexposure are inhalation of vapors, and ingestionand absorption of the liquid throughthe skin. Serious health hazards may arisefrom chronic inhalation, which may causekidney and liver damage, and stimulationof bone marrow to increase the productionof blood platelets. Low-level exposureto 10 ppm may produce chronic poisoningeffects on the central nervous system. Ingestionof the liquid may produce the samesymptoms as those stated above. Skin contactcan cause dermatitis. Vapor is an irritantto the eyes, nose, and lungs. Because of itsstrong disagreeable odor, there is always asufficient warning against any overexposure.A concentration of 10 ppm is objectionableto humans.
LCLO value, inhalation (rats): 4000 ppm/4 h
LD50 value, oral (mice): 1500 mg/kg.
Huh and coworkers (1986) have investigatedthe effect of glycyrrhetinic acid on pyridine toxicity in mice. Pretreatmentwith glycyrrhetinic acid decreaseddepression of the central nervous system andmortality in animals induced by pyridine.Such pretreatment markedly decreased theactivity of the enzyme serum transaminase, and increased the activity of hepaticmicrosomal aniline hydroxylase [9012-90-0], a pyridine- metabolizing enzyme.

Fire Hazard

Behavior in Fire: Vapor is heavier than air and may travel considerable distance to source of ignition and flash back.

Fire Hazard

Pyridine is a highly flammable liquid (NFPA rating = 3), and its vapor can travel a considerable distance and "flash back." Pyridine vapor forms explosive mixtures with air at concentrations of 1.8 to 12.4% (by volume). Carbon dioxide or dry chemical extinguishers should be used for pyridine fires.

Flammability and Explosibility

Pyridine is a highly flammable liquid (NFPA rating = 3), and its vapor can travel a considerable distance and "flash back." Pyridine vapor forms explosive mixtures with air at concentrations of 1.8 to 12.4% (by volume). Carbon dioxide or dry chemical extinguishers should be used for pyridine fires.

Industrial uses

Pyridine is a good solvent for a large number of compounds, both organic and inorganic (Windholz et al 1983). About 50% of pyridine used in the U.S. is for the production of agricultural chemicals, such as the herbicides paraquat, diquat and triclopyr and the insecticide chlorpyrifos. Other uses are in the production of piperidine; the manufacture of pharmaceuticals, such as steroids, vitamins and antihistamines; and as a solvent. Solvent uses are found in both the pharmaceutical and polycarbonate resin industries. It is particularly useful as a solvent in processes where HC1 is evolved (Santodonato et al 1985). Minor uses for pyridine are for the denaturation of alcohol and antifreeze mixtures, as a dyeing assistant in textiles and as a flavoring agent (Jori et al 1983; Furia 1968; HSDB 1988).

Contact allergens

Pyridine (unsubstituted pyridine) and its derivative (substituted pyridines) are widely used in chemistry. Pyridine is a solvent used for many organic compounds and anhydrous metallic salt chemicals. Contained in Karl Fischer reagent, it induced contact dermatitis in a laboratory technician. No cross-sensitivity is observed between those different substances.

Safety Profile

Poison by intraperitoneal route. Moderately toxic by ingestion, skin contact, intravenous, and subcutaneous routes. Mildly toxic by inhalation. A skin and severe eye irritant. Mutation data reported. Can cause central nervous system depression, gastrointestinal upset, and liver and kidney damage. A flammable liquid and dangerous fire hazard when exposed to heat, flame, or oxidizers. Severe explosion hazard in the form of vapor when exposed to flame or spark. Reacts violently with chlorosulfonic acid, chromium trioxide, dinitrogen tetraoxide, HNO3, oleum, perchromates, ppropiolactone, AgClO4, H2SO4. Incandescent reaction with fluorine. Reacts to form pyrophoric or explosive products with bromine trifluoride, trifluoromethyl hypofluorite. Mixtures with formamide + iodine + sulfur trioxide are storage hazards, releasing carbon dioxide and sulfuric acid. Incompatible with oxidizing materials. Reacts with maleic anhydride (above 150°C) evolving carbon dioxide. To fight fire, use alcohol foam. When heated to decomposition it emits highly toxic fumes of NOx.

Potential Exposure

Pyridine is used as a solvent in the chemical industry and as a denaturant for ethyl alco- hol; as an intermediate in the production of pesticides; in pharmaceuticals; in the manufacture of paints, explosives, dyestuffs, rubber, vitamins, sulfa drugs; and disinfectants.

Enzyme inhibitor

This aromatic nitrogen heterocycle (FW = 79.101 g/mol; CAS 110-86-1; colorless; M.P. = –41.5° C; B.P. = 115.25° C; unpleasant odor; weak base; pKa = 5.23 at 25° C, with dpKa/dT = –0.014) has many uses in organic synthesis and analytical chemistry. Pyridine should only be used in a fume hood or where there is sufficient ventilation. Miscible with water, pyridine has a larger dipole moment (2.37 versus 1.87 for water), and a dielectric constant of 12.4 (a sixth that of water). Target (s) : acid phosphatase; adenain; alcohol dehydrogenase; D-amino-acid oxidase, weakly inhibited; aromatase, or CYP19; carbonic anhydrase, or carbonate dehydratase, Ki ≈ 0.5 M; catechol 2,3-dioxygenase; chymotrypsin; dimethylaniline-N-oxide aldolase; glucose dehydrogenase, weakly inhibited; histidine decarboxylase, Ki = 1.4 mM; lipase, or triacylglycerol lipase; nicotinate phosphoribosyltransferase; and xyloglucan:xyloglucosyl transferase .

First aid

If this chemical gets into the eyes, remove any contact lenses at once and irrigate immediately for at least 15 minutes, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical contacts the skin, remove contaminated clothing and wash immediately with soap and water. Seek medical attention immediately. If this chemical has been inhaled, remove from exposure, begin rescue breathing (using universal precautions, includ- ing resuscitation mask) if breathing has stopped and CPR if heart action has stopped. Transfer promptly to a medical facility. When this chemical has been swallowed, get medical attention. Give large quantities of water and induce vomiting. Do not make an unconscious person vomit.


Pyridine is absorbed through the gastrointestinal tract, skin and lungs and is eliminated via the urine, feces, skin and lungs, both as metabolites and as the parent compound (Jori et al 1983). Uptake by tissues increases with dose and the elimination is biphasic in nature (Zharikov and Titov 1982; HSDB 1988). Elimination is rapid and there appears to be no tissue accumulation (Jori et al 1983). The observation by His (1887) of the urinary excretion of Af-methylpyridine by pyridine-dosed animals was the first example of Af-methylation. Known urinary metabolites of pyridine in mammals now include pyridine N-oxide, N-methyl pyridine, 4-pyridone, 2-pyridone and 3-hydroxypyridine. Some metabolites still remain to be identified (Damani et al 1982). The relative amounts of the metabolites are highly dependent on the species and dose (Gorrod and Damani 1980). For example, the rat has been shown to excrete 70% of a 1 mg/kg dose in the urine in the first 24 h after dosing, but that figure drops to only 5.8% for a 500 mg/kg dose (D'Souza et al 1980). Although urinary excretion of pyridine and its metabolites appears to be a major route for elimination, non-urinary excretion has not been extensively studied (Santodonato et al 1985). In rabbits, the pyridine N-methyltransferase activity has been shown to be highest in lung cytosol and it has been found to utilize 5-adenosyl methionine as the methyl donor (Damani et al 1986). This pathway is saturable in both the rat and the guinea pig (D'Souza et al 1980). The product of this reaction, N-methyl pyridine, is less chronically toxic but more acutely toxic than pyridine (Williams 1959). Pyridine N-oxide is produced by the cytochrome P-450 system and the activity is induced by phenobarbital or pyridine pretreatment but not by 3-methylcholanthrene (Gorrod and Damani 1979; Kaul and Novak 1987). In the rabbit, the alcohol-inducible (and pyridine inducible) P-450 LM3A appears to be the low Km isozyme which catalyzes pyridine Af-oxide production (Kim and Novak 1989). The N-oxidation of pyridine may represent a pathway for bioactivation (Santodonato et al 1985) and this pathway becomes more important as the pyridine dose is increased (Damani et al 1982).


Pyridine should be used only in areas free of ignition sources, and quantities greater than 1 liter should be stored in tightly sealed metal containers in areas separate from oxidizers.


UN1992 Flammable liquids, toxic, n.o.s., Hazard Class: 3; Labels: 3-Flammable liquid, 6.1-Poisonous mate- rials, Technical Name Required.

Purification Methods

Likely impurities are H2O and amines such as the picolines and lutidines. Pyridine is hygroscopic and is miscible with H2O and organic solvents. It can be dried with solid KOH, NaOH, CaO, BaO or sodium, followed by fractional distillation. Other methods of drying include standing with Linde type 4A molecular sieves, CaH2 or LiAlH4, azeotropic distillation of the H2O with toluene or *benzene, or treated with phenylmagnesium bromide in ether, followed by evaporation of the ether and distillation of the pyridine. A recommended [Lindauer & Mukherjee Pure Appl Chem 27 267 1971] method dries pyridine over solid KOH (20g/Kg) for 2weeks and fractionally distils the supernatant over Linde type 5A molecular sieves and solid KOH. The product is stored under CO2-free nitrogen. Pyridine can be stored in contact with BaO, CaH2 or molecular sieves. Non-basic materials can be removed by steam distilling a solution containing 1.2 equivalents of 20% H2SO4 or 17% HCl until about 10% of the base has been carried over along with the non-basic impurities. The residue is then made alkaline, and the base is separated, dried with NaOH and fractionally distilled. Alternatively, pyridine can be treated with oxidising agents. Thus pyridine (800mL) has been stirred for 24hours with a mixture of ceric sulfate (20g) and anhydrous K2CO3 (15g), then filtered and fractionally distilled. Hurd and Simon [J Am Chem Soc 84 4519 1962] stirred pyridine (135mL), water (2.5L) and KMnO4 (90g) for 2hours at 100o, then stood for 15hours before filtering off the precipitated manganese oxides. Addition of solid KOH (ca 500g) caused pyridine to separate. It was decanted, refluxed with CaO for 3hours and distilled. Separation of pyridine from some of its homologues can be achieved by crystallisation of the oxalates. Pyridine is precipitated as its oxalate by adding it to the stirred solution of oxalic acid in acetone. The precipitate is filtered, washed with cold acetone, and pyridine is regenerated and isolated. Other methods are based on complex formation with ZnCl2 or HgCl2. Heap, Jones and Speakman [J Am Chem Soc 43 1936 1921] added crude pyridine (1L) to a solution of ZnCl2 (848g) in 730mL of water, 346mL of conc HCl and 690mL of 95% EtOH. The crystalline precipitate of ZnCl2.(pyridine)2 was filtered off, recrystallised twice from absolute EtOH, then treated with a conc NaOH solution, using 26.7g of solid NaOH to 100g of the complex. The precipitate was filtered off, and the pyridine was dried with NaOH pellets and distilled. Similarly, Kyte, Jeffery and Vogel [J Chem Soc 4454 1960] added pyridine (60mL) in 300mL of 10% (v/v) HCl to a solution of HgCl2 (405g) in hot water (2.3L). On cooling, crystals of pyridine-HgCl2 (1:1) complex separated and were filtered off, crystallised from 1% HCl (to m 178.5-179o), washed with a little EtOH and dried at 110o. The free base was liberated by addition of excess aqueous NaOH and separated by steam distillation. The distillate was saturated with solid KOH, and the upper layer was removed, dried further with KOH, then BaO and distilled. Another possible purification step is fractional crystallisation by partial freezing. Small amounts of pyridine have been purified by vapour-phase chromatography, using a 180-cm column of polyethyleneglycol-400 (Shell 5%) on Embacel at 100o, with argon as carrier gas. The Karl Fischer titration can be used for determining water content. A colour test for pyrrole as a contaminant is described by Biddiscombe et al. [J Chem Soc 1957 1954]. The 1:1-hydrochloride crystallises from EtOH with m 144o, b 218-219o/760mm (see below) and is hygroscopic. The 1:2-hydrochloride has m 46o [58888-58-7] and the picrate has m 165-166o [1152-90-5]. [Beilstein 20 H 181, 20 I 54, 20 II 96, 20 III/IV 2205, 20/5 V 160.] § Polystyrene-supported pyridine is commercially available.


Violent reaction with strong oxidizers; strong acids; chlorosulfonic acid; maleic anhydride; oleum iodine.

Waste Disposal

Controlled incineration whereby nitrogen oxides are removed from the effluent gas by scrubber, catalytic or thermal devices .

Pyridine Preparation Products And Raw materials

Raw materials

Preparation Products

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2019-04-09 Pyridine
US $100.00 / KG 100g 99.8% 5tons Hebei Jimi Trading Co., Ltd.
2019-05-15 Pyridine pyridine CAS NO.110-86-1 PY kf-wang(at)
US $25.00 / Kg/Drum 10g 99.8% 2000 Hebei Aicrowe Biotech Co., Ltd
2018-12-17 Pyridine
US $7.00 / kg 1kg 99% 100kg career henan chemical co

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