2-vinylpyridine

2-Vinylpyridine is an organic compound with the formula CH2CHC5H4N. It is a derivative of pyridine with a vinyl group in the 2-position, next to the nitrogen. It is a colorless liquid, although samples are often brown. It is used industrially as a precursor to specialty polymers and as an intermediate in the chemical, pharmaceutical, dye, and photo industries. Vinylpyridine is sensitive to polymerization. It may be stabilized with a polymerisation inhibitor such as tert-butylcatechol. Owing to its tendency to polymerize, samples are typically refrigerated.

==Synthesis== It was first synthesized in 1887. A contemporary preparation entails condensation of 2-methylpyridine with formaldehyde, followed by dehydration of the intermediate alcohol. The reaction is carried out between 150–200 °C in an autoclave. The conversion is kept relatively low. After removal of unreacted 2-methylpyridine by distillation, concentrated aqueous sodium hydroxide is added to the residue and the resultant mixture is distilled under reduced pressure. During distillation, the dehydration of 2-(2-pyridyl)ethanol occurs to give 2-vinylpyridine, which can be purified further by fractional distillation under reduced pressure in the presence of an inhibitor such as 4-tert-butylcatechol. CH3C5H4N + CH2O → HOCH2CH2C5H4N HOCH2CH2C5H4N → CH2=CHC5H4N + H2O