DABCO

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DABCO
Names
IUPAC name
1,4-Diazabicyclo[2.2.2]octane
Other names
triethylenediamine, TEDA
DABCO
Identifiers
280-57-9 YesY
ChemSpider 8882 YesY
2577
Jmol 3D model Interactive image
Interactive image
PubChem 9237
Properties
C6H12N2
Molar mass 112.18 g·mol−1
Appearance White crystalline powder
Melting point 156 to 160 °C (313 to 320 °F; 429 to 433 K)
Boiling point 174 °C (345 °F; 447 K)
Soluble, hygroscopic
Acidity (pKa) 3.0, 8.8 (in water)[1]
Vapor pressure {{{value}}}
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

DABCO is the acronym for the organic compound 1,4-diazabicyclo[2.2.2]octane, with the formula N2(C2H4)3. This colorless solid is a highly basic amine, which is used as a catalyst and reagent in polymerization and organic synthesis.[2]

Reactions and applications

The pKa of [HDABCO]+ (the protonated derivative) is 8.8, which is almost the same as ordinary alkylamines. The nucleophilicity of the amine is high because the amine centers are unhindered. It is sufficiently basic to promote C-C coupling of terminal acetylenes, for example, phenylacetylene couples with electron-deficient iodoarenes.

Example of a DABCO-catalysed C-C coupling

Catalyst

DABCO is used as a base-catalyst for:

The scheme of Baylis Hilman reaction.

Lewis base

As an unhindered amine, it is a strong ligand and Lewis base. it forms a crystalline 2:1 adduct with hydrogen peroxide[5] and sulfur dioxide.[6]

Quencher of singlet oxygen

DABCO and related amines are quenchers of singlet oxygen and effective antioxidants,[7] and can be used to improve the lifetime of dyes. This makes DABCO useful in dye lasers and in mounting samples for fluorescence microscopy (when used with glycerol and PBS).[8] DABCO can also be used to demethylate quaternary ammonium salts by heating in dimethylformamide (DMF).[9]

Production

It is produced by thermal reactions of compounds of the type H2NCH2CH2X (X = OH, NH2, NHR) in the presence of zeolitic catalysts. An idealized conversion is shown for the conversion from ethanolamine:[10]

3 H2NCH2CH2OH → N(C2H4)3N + NH3 + 3 H2O

References

  1. D. H. Ripin, D. A. Evans (2002). "pKa's of Nitrogen Acids" (PDF).<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  2. Uppuluri V. Mallavadhani, Nicolas Fleury-Bregeot "1,4-Diazabicyclo [2.2.2]octane" Encyclopedia of Reagents for Organic Synthesis, 2010, John Wiley & Sons, Ltd. doi:10.1002/047084289X.rd010m.pub2
  3. "Polyurethane additives guide" (PDF). Air Products & Chemicals.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  4. Baylis, A. B.; Hillman, M. E. D. German Patent 2155113, 1972.
  5. P. Dembech, A. Ricci, G. Seconi, and M. Taddei "Bis(trimethylsilyl) Peroxide" Org. Synth. 1997, volume 74, pp. 84. doi:10.15227/orgsyn.074.0084
  6. Ludovic Martial and Laurent Bischoff "Preparation of DABSO from Karl-Fischer Reagent" Org. Synth. 2013, volume 90, pp. 301. doi:10.15227/orgsyn.090.0301
  7. Ouannes, C.;, Wilson, T. (1968). "Quenching of singlet oxygen by tertiary aliphatic amines. Effect of DABCO (1,4-diazabicyclo[2.2.2]octane)". Journal of the American Chemical Society. 90 (23): 6527–6528. doi:10.1021/ja01025a059.CS1 maint: multiple names: authors list (link)<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  8. Valnes, K.; Brandtzaeg, P. (1985). "Retardation of immunofluorescence fading during microscopy" (pdf). Journal of Histochemistry and Cytochemistry. 33 (8): 755–761. PMID 3926864.CS1 maint: multiple names: authors list (link)<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  9. Ho, T. L. (1972). "Dealkylation of Quaternary Ammonium Salts with 1,4-Diazabicyclo[2.2.2]octane". Synthesis. 1972 (12): 702. doi:10.1055/s-1972-21977.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  10. Karsten Eller, Erhard Henkes, Roland Rossbacher, Hartmut Höke "Amines, Aliphatic" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005. doi:10.1002/14356007.a02_001

Further reading

  • Cecchi, L.; DeSarlo, F.; Machetti, F. (2006). "1,4-Diazabicyclo[2.2.2]octane (DABCO) as an Efficient Reagent for the Synthesis of Isoxazole Derivatives from Primary Nitro Compounds and Dipolarophiles: The Role of the Base". European Journal of Organic Chemistry. 2006 (21): 4852–4860. doi:10.1002/ejoc.200600475.CS1 maint: multiple names: authors list (link)<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>.