2,6-Dimethylnaphthalene

2,6-Dimethylnaphthalene (2,6-DMN) is a polycyclic aromatic hydrocarbon. It is one of the ten dimethylnaphthalene isomers, which are derived from naphthalene by the addition of two methyl groups.[1]

2,6-Dimethylnaphthalene
Names
Preferred IUPAC name
2,6-Dimethylnaphthalene
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.008.605
UNII
  • InChI=1S/C12H12/c1-9-3-5-12-8-10(2)4-6-11(12)7-9/h3-8H,1-2H3
    Key: YGYNBBAUIYTWBF-UHFFFAOYSA-N
  • InChI=1/C12H12/c1-9-3-5-12-8-10(2)4-6-11(12)7-9/h3-8H,1-2H3
    Key: YGYNBBAUIYTWBF-UHFFFAOYAZ
  • Cc1ccc2cc(ccc2c1)C
Properties
C12H12
Molar mass 156.228 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Synthesis

Alkylated naphthalenes (methyl-, dimethyl-, and poly-methyl naphthalenes, thus including 2,6-DMN) are found in low concentrations in crude oil and coal tar. Separation is difficult, expensive, and requires a number of operations such as selective crystallization and adsorption, in addition to any isomerization reactions. Alternative routes to 2,6-DMN remains of interest.[2]

In the "alkenylation process" butadiene (1), o-xylene (2), and sodium-potassium alloy (3) are used, which react to form 5-(ortho-tolyl)pent-2-ene (OTP, 3).[3] OTP is subsequently cyclized to 1,5-dimethyltetraline (4). Dehydrogenation then provides 1,5-dimethylnaphthalene (1,5-DMN, 5). Finally, 1,5-DMN is isomerized to 2,6-DMN (6). In the final step, other mono-, di-, and tri-methylnaphthalenes are formed. More work is therefore required in separation of the mixture, which is done by selective crystallization.

Synthesis of 2,6-dimethylnaphthalene by the alkenylation process

Applications

2,6-Dimethylnaphthalene is mainly used for the preparation of 2,6-naphthalenedicarboxylic acid by oxidation of 2,6-dimethylnaphthalene in the liquid phase. 2,6-Naphthalenedicarboxylic acid is a monomer for the production of high-performance polymers, in particular poly (ethylene-2,6-naphthalene dicarboxylate) or shorter polyethylene naphthalate (PEN).[4] That polyester is stronger and has a higher thermal resistance than the more frequently used polyethylene terephthalate (PET).

2,6-Dimethylnaphthalene undergoes ammoxidation to give the 2,6-dicyanonaphthalene, which can be hydrogenated to bis(aminomethyl)naphthalene, a precursor to dyes.[5]

References
  1. Collin, Gerd; Höke, Hartmut; Greim, Helmut (2003). "Naphthalene and Hydronaphthalenes". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a17_001.pub2.
  2. US patent 5004853, Paul T. Barger, Timothy J. Barder, David Y. Lin, Simon H. Hobbs, "Continuous process for the production of 2,6-dimethylnaphthalene", issued April 2, 1991
  3. US patent, Lawrence D. Lillwitz, Anne M. Karachewski, "Alkylation of alkylaromatics promoted by sonicated alkali metal", issued March 30, 1993
  4. Lillwitz, L. D. (2001). "Production of Dimethyl-2,6-Naphthalenedicarboxylate: Precursor to Polyethylene Naphthalate". Applied Catalysis A: General. 221 (1–2): 337–358. doi:10.1016/S0926-860X(01)00809-2.
  5. Pollak, Peter; Romeder, Gérard; Hagedorn, Ferdinand; Gelbke, Heinz-Peter (2000). "Nitriles". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a17_363.
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.