|Jmol interactive 3D||Image
|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)|
|Acidity (pKa)||3.0, 8.8 (in water)|
|H228, H302, H315, H319, H335, H412|
|P210, P261, P273, P305 + P351 + P338|
|R-phrases||R11, R22, R36/37/38, R52/53|
|Flash point||62 °C (144 °F; 335 K)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
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.
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.
DABCO is used as a base-catalyst for:
- formation of polyurethane from amines and isocyanates. In factDABCO is a registered trademark of Air Products & Chemicals Inc for this application.
- Baylis-Hillman and Morita-Baylis-Hilman reactions of aldehydes and unsaturated ketones and aldehydes.
Quencher of singlet oxygen
DABCO and related amines are quenchers of singlet oxygen and effective antioxidants, 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). DABCO can also be used to demethylate quaternary ammonium salts by heating in dimethylformamide (DMF).
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:
- 3 H2NCH2CH2OH → N(C2H4)3N + NH3 + 3 H2O
- D. H. Ripin, D. A. Evans (2002). "pKa's of Nitrogen Acids" (PDF).
- "Safety data for 1,4-diazabicyclo[2.2.2]octane (see MSDS)". Sigma-Aldrich.
- 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
- "Polyurethane additives guide" (PDF). Air Products & Chemicals.
- Baylis, A. B.; Hillman, M. E. D. German Patent 2155113, 1972.
- 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
- 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
- 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.
- Valnes, K.; Brandtzaeg, P. (1985). "Retardation of immunofluorescence fading during microscopy" (pdf). Journal of Histochemistry and Cytochemistry 33 (8): 755–761. PMID 3926864.
- 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.
- 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
- 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..