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Chemical compound From Wikipedia, the free encyclopedia
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.
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Names | |
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Preferred IUPAC name
2,6-Dimethylpyridine | |
Other names
Lutidine | |
Identifiers | |
3D model (JSmol) |
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105690 | |
ChEBI | |
ChemSpider | |
ECHA InfoCard | 100.003.262 |
EC Number |
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2863 | |
PubChem CID |
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UNII | |
UN number | 2734 |
CompTox Dashboard (EPA) |
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Properties | |
C7H9N | |
Molar mass | 107.153 g/mol |
Appearance | colorless oily liquid |
Density | 0.9252 |
Melting point | −5.8 °C (21.6 °F; 267.3 K) |
Boiling point | 144 °C (291 °F; 417 K) |
27.2% at 45.3 °C | |
Acidity (pKa) | 6.72[2] |
−71.72×10−6 cm3/mol | |
Hazards | |
NFPA 704 (fire diamond) | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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.[3]
It is produced industrially by the reaction of formaldehyde, acetone, and ammonia.[2]
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:
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]
Like most alkylpyridines, the LD50 of 2,6-dimethylpyridine is modest, being 400 mg/kg (oral, rat).[2]