3-Methylpyridine

3-Methylpyridine

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Names
Other names 3-picoline
Identifiers
CAS Number	108-99-6 Y
ChEBI	CHEBI:39922 Y
ChEMBL	ChEMBL15722 N
ChemSpider	7682 Y
Jmol 3D model	Interactive image
InChI InChI=1S/C6H7N/c1-6-3-2-4-7-5-6/h2-5H,1H3 Key: ITQTTZVARXURQS-UHFFFAOYSA-N
SMILES Cc1cccnc1
Properties
Chemical formula	C6H7N
Molar mass	93.13 g/mol
Appearance	Colorless liquid
Density	0.957 g/mL
Melting point	−19 °C (−2 °F; 254 K)
Boiling point	144 °C (291 °F; 417 K)
Solubility in water	Miscible
Vapor pressure	{{{value}}}
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)
Infobox references

3-Methylpyridine or 3-picoline, is an organic compound with formula 3-CH₃C₅H₄N. It is one of three isomers of methylpyridine. This colorless liquid is a precursor to pyridine derivatives that have applications in the pharmaceutical and agricultural industries. Like pyridine, 3-methylpyridine is a colorless liquid with a strong odor. It is classified as a weak base.

Synthesis

3-Methylpyridine is produced industrially by the reaction of acrolein with ammonia:

2 CH₂CHCHO + NH₃ → 3-CH₃C₅H₄N + 2 H₂O

This reaction is nonselective and a more efficient route starts with acrolein, propionaldehyde, and ammonia:

CH₂CHCHO + CH₃CH₂CHO + NH₃ → 3-CH₃C₅H₄N + 2 H₂O + H₂

It may also be obtained as a co-product of pyridine synthesis from acetaldehyde, formaldehyde, and ammonia via Chichibabin pyridine synthesis. Approximately 9,000,000 kilograms were produced worldwide in 1989.

Uses

3-Picoline is a useful precursor to agrochemicals, such as chlorpyrifos. Chlorpyrifos is produced from 3,5,6-trichloro-2-pyridinol, which is generated from 3-picoline by way of cyanopyridine. This conversion involves the ammoxidation of 3-methylpyridine:

3-CH₃C₅H₄N + 1.5 O₂ + NH₃ → 3-NCC₅H₄N + 3 H₂O

3-Cyanopyridine is also a precursor to 3-pyridinecarboxamide, which is a precursor to pyridinecarbaldehydes:

3-NCC₅H₃N + [H] + catalyst → 3-HC(O)C₅H₄N

Pyridinecarbaldehydes are used to make antidotes for poisoning by organophosphate acetylcholinesterase inhibitors.

Environmental Behavior

Pyridine derivatives (including 3-methylpyridine) are environmental contaminants, generally associated with processing fossil fuels, such as oil shale or coal. They are also found in the soluble fractions of crude oil spills. They have also been detected at legacy wood treatment sites. The high water solubility of 3-methyl pyridine increases the potential for the compound to contaminate water sources. 3-methyl pyridine is biodegradable, although it degrades more slowly and volatilize more readily from water samples than either 2-methyl- or 4-methyl-pyridine.,

Niacin

3-Methylpyridine is the main precursor to niacin, one of the B vitamins. Niacin is the generic name for both nicotinic acid and nicotinamide (pyridine 3-carboxylic acid and pyridine 3-carboxylic acid amide). Nicotinic acid was first synthesized in 1867 by oxidative degradation of nicotine. Niacin is also an important food additive for domestic and farm animals; more than 60% of the niacin produced is consumed by poultry, swine, ruminants, fish, and pets. Along with its use as an essential vitamin, niacin is also a precursor to many of commercial compounds including cancer drugs, antibacterial agents, and pesticides. Approximately 10,000,000 kilograms of niacin are produced annually worldwide.

Niacin is prepared by hydrolysis of nicotinonitrile, which, as described above, is generated by oxidation of 3-picoline. Oxidation can be effected by air, but ammoxidation is more efficient. The catalysts used in the reaction above are derived from the oxides of antimony, vanadium, and titanium. New “greener” catalysts are being tested using manganese-substituted aluminophosphates that use acetyl peroxyborate as non-corrosive oxidant. The use of this catalyst/oxidizer combination is greener because it does not produce nitrogen oxides as do traditional ammoxidations.

See also

• Picoline