| 3-Methylpyridine | |
|---|---|
|
Other names
3-picoline |
|
| Identifiers | |
| CAS number | 108-99-6 |
| ChemSpider | 7682 |
| ChEMBL | CHEMBL15722 |
| Properties | |
| Molecular formula | C6H7N |
| Molar mass | 93.13 g/mol |
| Appearance | Colorless liquid |
| Density | 0.957 g/mL |
| Melting point |
-19 °C |
| Boiling point |
144 °C |
| Solubility in water | Miscible |
| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
3-Methylpyridine, or 3-picoline, is the organic compound with formula 3-CH3C5H4N. It is one of the 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 colourless liquid with a strong odor. It is classified as a weak base.
Contents |
3-Methylpyridine is produced industrially by the reaction of acrolein with ammonia:
This reaction is nonselective and a more efficient route starts with acrolein, propionaldehyde, and ammonia:
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. [1]
3-Picoline is a useful precursor to agrochemicals, such as chlorpyrifos.[2] 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-Cyanopyridine is also a precursor to 3-pyridinecarboxamide, which is an precursor to pyridinecarbaldehydes:
Pyridinecarbaldehydes are used to make antidotes for poisoning by organophosphate acetylcholinesterase inhibitors.
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.[3] 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.[3]
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.[3] 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.[4] The use of this catalyst/oxidizer combination is greener because it does not produce nitrogen oxides as do traditional ammoxidations.