1,8-Bis(dimethylamino)naphthalene
From Wikipedia, the free encyclopedia
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Properties |
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| Name | Proton spongeTM |
| Name (IUPAC name) | 1,8-Bis(dimethylamino)naphthalene |
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| Chemical formula | C14H18N 2 |
| Molecular weight | 214.3096 amu |
| CAS number | 20734-58-1 |
| Melting point | 47.8°C (321.0 K) |
| 1H-NMR(CCl4) | δ (ppm): 2.17(CH3), 6.74, 2.17(C10H8) |
| Acid dissociation constant:pKa | 12.34 |
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More information |
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| Properties | NIST WebBook |
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Unless otherwise stated, all data was produced under conditions of standard temperature and pressure. |
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1,8-Bis(dimethylamino)naphthalene is a chemical compound that was first prepared in 1968 by Roger Alder FRS at the University of Bristol. It is often referred by the trade name "Proton-sponge", a trademark of Aldrich Chemical Co., of Milwaukee, Wisconsin, USA [1] [2]. This compound is a diamine in which the two dimethylamino groups are attached on the same side or peri position of a naphthalene system. Proton-sponge has several very interesting properties; one is its very high basicity; another is its spectroscopic properties.
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[edit] High basicity
Proton-sponge has one of the highest Brønsted base values; the conjugate acid has a pKa of 12.34 in aqueous solution. But its basic power is intensely powerful. This makes it one of the strongest amine bases known, although it only absorbs protons slowly - hence the trade name. The high basicity is attributed to the relief of strain upon protonation and/or the strong interaction between the nitrogen lone pairs1. However the molecule is sterically hindered, making it a weak nucleophile, yet a strong base. Because of this combination of properties, Proton-sponge has been used in organic synthesis as a highly selective non-nucleophilic base.
[edit] Spectroscopic properties
The spectroscopic properties of Proton-sponge are very interesting for researchers of molecular chemistry and have been researched for a long time. Proton-sponge emits a double fluorescence in various solutions due to the mixture of two ground-state species2.
[edit] Trimethylated Proton-sponge
Proton-sponge is methylated by using dimethyl sulfate. The pKa of trimethylated Proton-sponge is 6.43 in aqueous solution.
[edit] Proton sponges
Second generation proton sponges are known with even higher basicity. 1,8-Bis(hexamethyltriaminophosphazenyl)naphthalene or HMPN [3] is prepared from 1,8-Bis(dimethylamino)naphthalene by reaction with Tris(dimethylamino)phosphine. HMPN has a pKBH+ of 29.9 in acetonitrile which is 12 orders of magnitude higher than Proton Sponge.
[edit] External links
[edit] References
- ^ F. Gerson, E.Haselbach, G. Plattner (December 1971). "Radical anion of 1,8-bis(dimethylamino)naphthalene ("proton sponge")". Chem. Phys. Lett. 12 (2): 316–319.
- ^ A. Szemik-Hojniak, W.Rettig, I. Deperasinska (2001-08-03). "The forbidden emission of protonated proton sponge". Chem. Phys. Lett. 343 (3): 404–412. DOI:10.1016/S0009-2614(01)00690-X.
- ^ Volker Raab, Ekaterina Gauchenova, Alexei Merkoulov, Klaus Harms, Jörg Sundermeyer, Borislav Kovačević, and Zvonimir B. Maksić (2005). "1,8-Bis(hexamethyltriaminophosphazenyl)naphthalene, HMPN: A Superbasic Bisphosphazene "Proton Sponge"". J. Am. Chem. Soc. 127 (45): 15738–15743. DOI:10.1021/ja052647v.
