:DABCO

{{chembox

|Section1 = {{Chembox Identifiers

|IUPHAR_ligand = 2577

|ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

|ChemSpiderID = 8882

|InChI = 1S/C6H12N2/c1-2-8-5-3-7(1)4-6-8/h1-6H2

|InChIKey = IMNIMPAHZVJRPE-UHFFFAOYSA-N

|InChI1 = 1/C6H12N2/c1-2-8-5-3-7(1)4-6-8/h1-6H2

|InChIKey1 = IMNIMPAHZVJRPE-UHFFFAOYAP

|SMILES1 = N12CCN(CC1)CC2

|CASNo_Ref = {{cascite|correct|CAS}}

|CASNo = 280-57-9

|EC_number = 205-999-9

|ChEMBL = 3183414

|ChEBI = 151129

|UNII_Ref = {{fdacite|correct|FDA}}

|UNII = X8M57R0JS5

|PubChem = 9237

|StdInChI_Ref = {{stdinchicite|correct|chemspider}}

|StdInChI = 1S/C6H12N2/c1-2-8-5-3-7(1)4-6-8/h1-6H2

|StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}

|StdInChIKey = IMNIMPAHZVJRPE-UHFFFAOYSA-N

|SMILES = C1CN2CCN1CC2

}}

| Section2 = {{Chembox Properties

|C=6 | H=12 | N=2

|Appearance = White crystalline powder

|MeltingPtC = 156 to 160

|BoilingPtC = 174

|pKa = 3.0, 8.8 (in water, for conjugated acid){{cite web |author= D. H. Ripin |author2= D. A. Evans |title= pKa's of Nitrogen Acids |year= 2002 |url= http://mysite.science.uottawa.ca/abeauche/chm4328/chm4328lecture2-evanspka_tables.pdf}}

|Solubility = Soluble, hygroscopic

}}

|Section3 = {{Chembox Hazards

|MainHazards = Harmful

|FlashPtC = 62

|GHSPictograms = {{GHS02}}{{GHS05}}{{GHS07}}

|GHSSignalWord = Danger

|HPhrases = {{H-phrases|228|302|315|319|335|412}}

|PPhrases = {{P-phrases|210|261|273|305+351+338}}

|NFPA-H = 2

|NFPA-F = 2

|NFPA-R = 1

|NFPA_ref = {{cite web |url= http://www.sigmaaldrich.com/catalog/product/sial/d27802?lang=en®ion=GB |title= Safety data for 1,4-diazabicyclo[2.2.2]octane (see MSDS) |publisher= Sigma-Aldrich}}

}}

|Section4 = {{Chembox Related | OtherCompounds =Quinuclidine
Tropane }}

|Watchedfields = changed

|verifiedrevid = 449935666

|ImageFileL1_Ref = {{chemboximage|correct|??}}

|ImageFileL1 = DABCO (bridgehead) V1.svg

|ImageFileR1 = DABCO-3D-balls.png

|ImageSizeR1 = 150 px

|PIN = 1,4-Diazabicyclo[2.2.2]octane

|OtherNames = Triethylenediamine, TEDA

}}

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.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}}

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.{{cite web |url= http://www.airproducts.com/~/media/Files/PDF/industries/en-pua-guide-americas.pdf |archive-url= https://web.archive.org/web/20160306222927/http://www.airproducts.com/~/media/Files/PDF/industries/en-pua-guide-americas.pdf |url-status= dead |archive-date= 2016-03-06 |title= Polyurethane additives guide |publisher= Air Products & Chemicals}}
Baylis–Hillman reactions of aldehydes and unsaturated ketones and aldehydes.Baylis, A. B.; Hillman, M. E. D. German Patent 2155113, 1972.

:File:Baylis Hilman Reaction Scheme.png

=Lewis base=

image:F-TEDA-BF4.svg|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.{{cite book |doi=10.1002/047084289X.rc116.pub2|chapter=1-(Chloromethyl)-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane Bis(tetrafluoroborate)|title=Encyclopedia of Reagents for Organic Synthesis|year=2007|last1=Banks|first1=R. Eric|last2=Murtagh|first2=Vincent|last3=An|first3=Ilhwan|last4=Maleczka|first4=Robert E.|isbn=978-0471936237}}

As an unhindered amine, it is a strong ligand and Lewis base. It forms a crystalline 2:1 adduct with hydrogen peroxideP. Dembech, A. Ricci, G. Seconi, and M. Taddei "Bis(trimethylsilyl) Peroxide" Org. Synth. 1997, volume 74, pp. 84. {{doi|10.15227/orgsyn.074.0084}} and sulfur dioxide.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}}

=Quencher of singlet oxygen=

DABCO and related amines are quenchers of singlet oxygen and effective antioxidants,{{cite journal |author= Ouannes, C. |author2= Wilson, T. |title= Quenching of singlet oxygen by tertiary aliphatic amines. Effect of DABCO (1,4-diazabicyclo[2.2.2]octane) |journal= Journal of the American Chemical Society |year= 1968 |volume= 90 |issue= 23 |pages= 6527–6528 |doi= 10.1021/ja01025a059|bibcode= 1968JAChS..90.6527O }} 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).{{cite journal |author= Valnes, K. |author2= Brandtzaeg, P. |title= Retardation of immunofluorescence fading during microscopy |journal= Journal of Histochemistry and Cytochemistry |volume= 33 |issue= 8 |pages= 755–761 |year= 1985 |pmid= 3926864 |doi= 10.1177/33.8.3926864 |doi-access= free }} DABCO can also be used to demethylate quaternary ammonium salts by heating in dimethylformamide (DMF).{{cite journal |author= Ho, T. L. |title= Dealkylation of Quaternary Ammonium Salts with 1,4-Diazabicyclo[2.2.2]octane |journal= Synthesis |year= 1972 |volume= 1972 |issue= 12 |pages= 702 |doi= 10.1055/s-1972-21977}}

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: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}}

: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.{{cite journal |author= Mahle, J. |display-authors=etal |title= Role of TEDA as an Activated Carbon Impregnant for the Removal of Cyanogen Chloride from Air Streams: Synergistic Effect with Cu(II) |journal= Journal of Physical Chemistry C |volume= 114 |issue= 47 |pages= 20083–20090 |year= 2010 |doi= 10.1021/jp106730j |url= https://pubs.acs.org/doi/10.1021/jp106730j |access-date= 2022-03-17}}