Picoline
Picoline refers to any of three isomers of methylpyridine (CH3C5H4N). They are all colorless liquids with a characteristic smell similar to that of pyridine. They are miscible with water and most organic solvents.
| Name(s) | CAS# | m.p. (°C) | b.p. (°C) | pKa of pyridinium ion | structure |
|---|---|---|---|---|---|
| 2-Methylpyridine, α-picoline, 2-picoline | [109-06-8] | -66.7 | 129.4 | 5.96 | |
| 3-Methylpyridine, β-picoline, 3-picoline | [108-99-6] | -18 | 141 | 5.63 | |
| 4-Methylpyridine, γ-picoline, 4-picoline | [108-89-4] | 3.6 | 145.4 | 5.98 | |
The CAS number of an unspecified picoline isomer is [1333-41-1]. The methyl group in 2- and 4- picolines is reactive; e.g., 2-picolines condenses with acetaldehyde in the presence of warm aqueous sodium hydroxide to form 2-propenylpyridine.
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