Английская Википедия:2,6-Lutidine

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2,6-Lutidine is a natural heterocyclic aromatic organic compound with the formula (CH3)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.[1]

A laboratory route involves condensation of ethyl acetoacetate, formaldehyde, and an ammonia source to give a bis(carboxy ester) of a 2,6-dimethyl-1,4-dihydropyridine, which, after hydrolysis, undergoes decarboxylation.[2]

It is produced industrially by the reaction of formaldehyde, acetone, and ammonia.[3]

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 less nucleophilic than pyridine. Protonation of lutidine gives lutidinium, [(CH3)2C5H3NH]+, salts of which are sometimes used as a weak acid because the conjugate base (2,6-lutidine) is so weakly coordinating. In a similar implementation, 2,6-lutidine is thus sometimes used in organic synthesis as a sterically hindered mild base.[4] One of the most common uses for 2,6-lutidine is as a non-nucleophilic base in organic synthesis. It takes part in the formation of silyl ethers as shown in multiple studies.[5][6]

Oxidation of 2,6-lutidine with air gives 2,6-diformylpyridine:

C5H3N(CH3)2 + 2 O2 → C5H3N(CHO)2 + 2 H2O

Biodegradation

The biodegradation of pyridines proceeds via multiple pathways.[7] 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.[8] Estimated time for complete degradation was over 30 days.[9]

See also

Toxicity

Like most alkylpyridines, the LD50 of 2,6-dimethylpyridine is modest, being 400 mg/kg (oral, rat).[3]

References

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