2,6-Lutidine
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| Names | |
|---|---|
| Preferred IUPAC name
2,6-Dimethylpyridine | |
| Other names
Lutidine
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| 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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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
[edit]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
[edit]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
[edit]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
[edit]Toxicity
[edit]Like most alkylpyridines, the LD50 of 2,6-dimethylpyridine is modest, being 400 mg/kg (oral, rat).[2]
References
[edit]- ^ a b The Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals (11th ed.), Merck, 1989, ISBN 091191028X, 5485
- ^ a b c Shimizu, Shinkichi; Watanabe, Nanao; Kataoka, Toshiaki; Shoji, Takayuki; Abe, Nobuyuki; Morishita, Sinji; Ichimura, Hisao (2007). "Pyridine and Pyridine Derivatives". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a22_399. ISBN 978-3527306732.
- ^ Singer, Alvin; McElvain, S. M. (1934). "2,6-Dimethylpyridine". Organic Syntheses. 14: 30. doi:10.15227/orgsyn.014.0030.
- ^ Prudhomme, Daniel R.; Park, Minnie; Wang, Zhiwei; Buck, Jason R.; Rizzo, Carmelo J. (2000). "Synthesis of 2′-Deoxyribonucleosides: Β-3′,5′-Di-o-benzoylthymidine". Org. Synth. 77: 162. doi:10.15227/orgsyn.077.0162.
- ^ Corey, E. J.; Cho, H.; Rücker, C.; Hua, D. H. (1981). "Studies with trialkylsilyltriflates: new syntheses and applications". Tetrahedron Letters. 22 (36): 3455–3458. doi:10.1016/s0040-4039(01)81930-4.
- ^ Franck, Xavier; Figadère, Bruno; Cavé, André (1995). "Mild deprotection of tert-butyl and tert-amyl ethers leading either to alcohols or to trialkylsilyl ethers". Tetrahedron Letters. 36 (5): 711–714. doi:10.1016/0040-4039(94)02340-H. ISSN 0040-4039.
- ^ Philipp, Bodo; Hoff, Malte; Germa, Florence; Schink, Bernhard; Beimborn, Dieter; Mersch-Sundermann, Volker (2007). "Biochemical Interpretation of Quantitative Structure-Activity Relationships (QSAR) for Biodegradation of N-Heterocycles: A Complementary Approach to Predict Biodegradability". Environmental Science & Technology. 41 (4): 1390–1398. Bibcode:2007EnST...41.1390P. doi:10.1021/es061505d. PMID 17593747.
- ^ Sims, G. K.; Sommers, L. E. (1985). "Degradation of pyridine derivatives in soil". Journal of Environmental Quality. 14 (4): 580–584. Bibcode:1985JEnvQ..14..580S. doi:10.2134/jeq1985.00472425001400040022x.
- ^ Sims, G. K.; Sommers, L. E. (1986). "Biodegradation of Pyridine Derivatives in Soil Suspensions". Environmental Toxicology and Chemistry. 5 (6): 503–509. doi:10.1002/etc.5620050601.