DABCO

DABCO
Names
	Preferred IUPAC name 1,4-Diazabicyclo[2.2.2]octane
	Other names Triethylenediamine, TEDA
Identifiers
CAS Number	280-57-9 ;
3D model (JSmol)	Interactive image; Interactive image;
ChEBI	CHEBI:151129;
ChEMBL	ChEMBL3183414;
ChemSpider	8882 ;
EC Number	205-999-9;
IUPHAR/BPS	2577;
PubChem CID	9237;
UNII	X8M57R0JS5 ;
	InChI InChI=1S/C6H12N2/c1-2-8-5-3-7(1)4-6-8/h1-6H2 Key: IMNIMPAHZVJRPE-UHFFFAOYSA-N ; InChI=1S/C6H12N2/c1-2-8-5-3-7(1)4-6-8/h1-6H2 Key: IMNIMPAHZVJRPE-UHFFFAOYSA-N; InChI=1/C6H12N2/c1-2-8-5-3-7(1)4-6-8/h1-6H2 Key: IMNIMPAHZVJRPE-UHFFFAOYAP;
	SMILES C1CN2CCN1CC2; N12CCN(CC1)CC2;
Properties
Chemical formula	C6H12N2
Molar mass	112.176 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)
Solubility in water	Soluble, hygroscopic
Acidity (pKa)	3.0, 8.8 (in water, for conjugated acid)
Hazards
Main hazards	Harmful
GHS pictograms
GHS Signal word	Danger
GHS hazard statements	H228, H302, H315, H319, H335, H412
GHS precautionary statements	P210, P261, P273, P305+351+338
NFPA 704 (fire diamond)	2 2 1
Flash point	62 °C (144 °F; 335 K)
Related compounds
Related compounds	Quinuclidine; Tropane
	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 (1,4-diazabicyclo[2.2.2]octane), also known as triethylenediamine or TEDA, is a bicyclic organic compound with the formula N₂(C₂H₄)₃. This colorless solid is a highly nucleophilic tertiary amine base, which is used as a catalyst and reagent in polymerization and organic synthesis.^[3]

It is similar in structure to quinuclidine, but the latter has one of the nitrogen atoms replaced by a carbon atom. Regarding their structures, both DABCO and quinuclidine are unusual in that the methylene hydrogen atoms are eclipsed within each of the three ethylene linkages. Furthermore, the diazacyclohexane rings, of which there are three, adopt the boat conformations, not the usual chair conformations.

Reactions

The pK_a 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 a variety of coupling reactions.

Catalyst

DABCO is used as a nucleophilic catalyst for:

formation of polyurethane from alcohol and isocyanate functionalized monomers and pre-polymers.^[4]
Baylis–Hillman reactions of aldehydes and unsaturated ketones and aldehydes.^[5]

Lewis base

thumb|left|110px The reagent Selectfluor is derived by alkylation of DABCO with dichloromethane following by treatment with fluorine. A colourless salt that tolerates air, Selectfluor has been commercialized for use for electrophilic fluorination.^[6]

As an unhindered amine, it is a strong ligand and Lewis base. It forms a crystalline 2:1 adduct with hydrogen peroxide^[7] and sulfur dioxide.^[8]

Quencher of singlet oxygen

DABCO and related amines are quenchers of singlet oxygen and effective antioxidants,^[9] 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).^[10] DABCO can also be used to demethylate quaternary ammonium salts by heating in dimethylformamide (DMF).^[11]

Production

It is produced by thermal reactions of compounds of the type H₂NCH₂CH₂X (X = OH, NH₂, or NHR) in the presence of zeolitic catalysts. An idealized conversion is shown for the conversion from ethanolamine:^[12]

3 H₂NCH₂CH₂OH → N(CH₂CH₂)₃N + NH₃ + 3 H₂O

Uses

In chemical and biological defense, activated carbon is impregnated with DABCO for use in filters for masks, collective protection systems, and the like.^[13]

References

↑ D. H. Ripin; D. A. Evans (2002). "pKa's of Nitrogen Acids". http://mysite.science.uottawa.ca/abeauche/chm4328/chm4328lecture2-evanspka_tables.pdf.
↑ "Safety data for 1,4-diazabicyclo[2.2.2octane (see MSDS)"]. Sigma-Aldrich. http://www.sigmaaldrich.com/catalog/product/sial/d27802?lang=en&region=GB.
↑ Uppuluri V. Mallavadhani, Nicolas Fleury-Bregeot. "1,4-Diazabicyclo [2.2.2]octane". In Encyclopedia of Reagents for Organic Synthesis, 2010, John Wiley & Sons, Ltd. doi:10.1002/047084289X.rd010m.pub2
↑ "Polyurethane additives guide". Air Products & Chemicals. http://www.airproducts.com/~/media/Files/PDF/industries/en-pua-guide-americas.pdf.
↑ Baylis, A. B.; Hillman, M. E. D. German Patent 2155113, 1972.
↑ Banks, R. Eric; Murtagh, Vincent; An, Ilhwan; Maleczka, Robert E. (2007). "1-(Chloromethyl)-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane Bis(tetrafluoroborate)". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rc116.pub2. ISBN 978-0471936237.
↑ 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". Journal of Histochemistry and Cytochemistry 33 (8): 755–761. doi:10.1177/33.8.3926864. 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
↑ Mahle, J. (2010). "Role of TEDA as an Activated Carbon Impregnant for the Removal of Cyanogen Chloride from Air Streams: Synergistic Effect with Cu(II)". Journal of Physical Chemistry C 114 (47): 20083–20090. doi:10.1021/jp106730j. https://pubs.acs.org/doi/10.1021/jp106730j. Retrieved 2022-03-17.

DABCO

Topic: Chemistry

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