2,6-Lutidine


2,6-Lutidine is a natural heterocyclic aromatic organic compound with the formula 2C5H3N. It is one of several dimethyl-substituted derivative of pyridine, all of which are referred to as lutidines It is a colorless liquid with mildly basic properties and a pungent, noxious odor.

Occurrence and production

It was first isolated from the basic fraction of coal tar and from bone oil.
A laboratory route involves condensation of ethyl acetoacetate, formaldehyde, and an ammonia source to give a bis of a 2,6-dimethyl-1,4-dihydropyridine, which, after hydrolysis, undergoes decarboxylation.
It is produced industrially by the reaction of formaldehyde, acetaldehyde, and ammonia.

Uses

2,6-Lutidine has been evaluated for use as a food additive owing to its nutty aroma when present in solution at very low concentrations.
Due to the steric effects of the two methyl groups, 2,6-lutidine is only weakly nucleophilic. Protonation of lutidine gives lutidinium, +, salts of which are sometimes used as a weak acid because the conjugate base is so weakly coordinating. In a similar implementation, 2,6-lutidine is thus sometimes used in organic synthesis as a sterically hindered mild base.

Biodegradation

The biodegradation of pyridines proceeds via multiple pathways. Although pyridine is an excellent source of carbon, nitrogen, and energy for certain microorganisms, methylation significantly retards degradation of the pyridine ring. In soil, 2,6-lutidine is significantly more resistant to microbiological degradation than any of the picoline isomers or 2,4-lutidine. Estimated time for complete degradation was >30 days.