2,6-Lutidine
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 | |
|---|---|
| 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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| |
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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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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.[3]
It is produced industrially by the reaction of formaldehyde, acetone, and ammonia.[2]
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
2,6-Lutidine also finds application in the synthesis of Nifurpirinol [13411-16-0].[7]
Biodegradation
The biodegradation of pyridines proceeds via multiple pathways.[8] 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.[9] Estimated time for complete degradation was over 30 days.[10]