What Is Picoline?
Picoline, or methylpyridine, has the chemical formula C6H7N and a molecular weight of 93.13 g/mol. Found in bone oil and coal tar, picoline has three isomers: 2-picoline (2-methylpyridine), 3-picoline (3-methylpyridine), and 4-picoline (4-methylpyridine), also known respectively as o-picoline, m-picoline, and p-picoline.
Usage of Picoline
2-picoline serves as a raw material for polymers, pharmaceuticals, and dyes, including tire cord adhesives. 3-picoline is key in producing nicotinamide and insecticides, while 4-picoline aids in synthesizing isonicotinic acid. Picoline isomers are also components in solvents, disinfectants, and vulcanization accelerators.
Properties of Picoline
All picoline isomers are water, ethanol, and ether soluble. They react with metal salts and hydrogen halides to form additional compounds, and their oxidation or reduction leads to various pyridine derivatives. These isomers are colorless liquids with a pyridine-like odor, showing weak basicity. Their physical properties, such as density, melting, and boiling points, vary slightly among the isomers.
Other Information about Picoline
1. Synthesis Method of Picoline
2-picoline, isolated from coal tar in 1846, is now primarily synthesized from acetaldehyde and ammonia. 3-picoline is industrially produced from ammonia and acrolein, with chichibabin pyridine synthesis as an alternative method. 4-picoline is obtained using ammonia and acetaldehyde with oxide catalysts.
2. Picoline Reactions
2-picoline is a precursor to 2-vinylpyridine and the nitrification inhibitor nitrapyrine. Oxidation can produce picolinic acid. 3-picoline’s ammoxidation yields 3-cyanopyridine, leading to agricultural chemicals like chlorpyrifos. 4-picoline, through ammoxidation, produces 4-cyanopyridine, a precursor to pharmaceuticals including the tuberculosis drug isoniazid.