Hexahydro-1,3,5-triazine

"TACH" redirects here. For other uses, see tach (disambiguation).

In chemistry, hexahydro-1,3,5-triazine is a class of heterocyclic compounds with the formula (CH₂NR)₃. Known as aldehyde ammonias, these compounds characteristically crystallize with water. They are reduced derivatives of 1,3,5-triazine, which have the formula (CHN)₃, a family of aromatic heterocycles.

Structure of a trisubstituted hexahydrotriazine

They are also called triazacyclohexanes or TACH's, but this acronym is also applied to cis,cis-1,3,5-triaminocyclohexane.

Preparation

N,N',N''-trisubstituted hexahydro-1,3,5-triazines arise from the condensation of a primary amine and formaldehyde as illustrated by the route to 1,3,5-trimethyl-1,3,5-triazacyclohexane:

3 CH₂O + 3 H₂NMe → (CH₂NMe)₃ + 3 H₂O

The C-substituted derivatives are obtained by reaction of aldehydes and ammonia:^[1]

3 RCHO + 3 NH₃ → (RCHNH)₃ + 3 H₂O

1-Alkanolamines are intermediates in these condensation reactions.^[2]

RDX, an explosive, is a hexahydro-1,3,5-triazine.

The parent hexahydro-1,3,5-triazine (CH₂NH)₃ has been detected as an intermediate in the condensation of formaldehyde and ammonia. This reaction affords hexamethylene tetraamine.^[3] The N-substituted derivatives are more stable. These

Representative model reaction using N,N-dimethyl-p-phenylene diamine (1.1) and stoichiometric paraformaldehyde. Hemiaminal 1.2 is an intermediate to hexahydrotriazine 1.3.^[2]

The N,N',N"-triacyltriazines are trizines with acyl groups attached to the three nitrogen centers of the ring. These triacyltriazines arise from the reaction of hexamethylene tetraamine with acid chlorides or the condensation of amides with formaldehyde.^[4]

Structure

Unlike the parent triazines, the hexahydro derivatives are conformationally flexible.^[5]

Related compounds and derivatives

See also: Cis,cis-1,3,5-Triaminocyclohexane

Structure of (Me₃TACH)ScCl₃ viewed down the three-fold symmetry axis (color scheme: blue = N, green = Cl, gray = C).^[6]

Trimers of isocyanates are sometimes labeled as 2,4,6-trioxohexahydro-1,3,5-triazines. They have the formula (RNC(O))₃ and based on the isocyanuric (trione) tautomer of cyanuric acid.

The N,N',N"-hexahydro-1,3,5-triazines function as tridentate ligands, which are called TACH (triazacyclohexanes). Examples include Mo(CO)₃[(CH₂)₃(NMe)₃] formed from the TACH ligand and molybdenum hexacarbonyl.^[7]

Hexahydro-1,3,5-triazine polymers have also been synthesized.^[2]

References

1. Nielsen, Arnold T.; Atkins, Ronald L.; Moore, Donald W.; Scott, Robert; Mallory, Daniel; LaBerge, Jeanne M. (1973). "Structure and chemistry of the aldehyde ammonias. 1-Amino-1-alkanols, 2,4,6-trialkyl-1,3,5-hexahydrotriazines, and N,N-dialkylidene-1,1-diaminoalkanes". J. Org. Chem. 38 (19): 3288–3295. doi:10.1021/jo00959a010.
2. Garcia, J. M.; Jones, G. O.; Virwani, K.; McCloskey, B. D.; Boday, D. J.; Ter Huurne, G. M.; Horn, H. W.; Coady, D. J.; Bintaleb, A. M.; Alabdulrahman, A. M. S.; Alsewailem, F.; Almegren, H. A. A.; Hedrick, J. L. (2014). "Recyclable, Strong Thermosets and Organogels via Paraformaldehyde Condensation with Diamines". Science. 344 (6185): 732–5. Bibcode:2014Sci...344..732G. doi:10.1126/science.1251484. PMID 24833389. S2CID 28090009.
3. Richmond, H. H.; Myers, G. S.; Wright, George F. (1948). "The Reaction between Formaldehyde and Ammonia". Journal of the American Chemical Society. 70 (11): 3659–3664. doi:10.1021/ja01191a034.
4. Teeters, W. O.; Gradsten, M. A. (1950). "Hexahydro-1,3,5-tripropionyl-s-triazine". Org. Synth. 30: 51. doi:10.15227/orgsyn.030.0051.
5. Jewett, J. G., Breeyear, J. J., Brown, J. H., Bushweller, C. H. (2000). "Stereodynamics of 1,3,5-Trialkyl-1,3,5-triazacyclohexanes: ¹H and ¹³C Dynamic NMR Studies. Solvent Effects. Ab Initio and Molecular Mechanics Calculations". J. Am. Chem. Soc. 122 (2): 308. doi:10.1021/ja990760d.{{cite journal}}: CS1 maint: multiple names: authors list (link)
6. Tredget, Cara S.; Lawrence, Sally C.; Ward, Benjamin D.; Howe, Robert G.; Cowley, Andrew R.; Mountford, Philip (2005). "A Family of Scandium and Yttrium Tris((trimethylsilyl)methyl) Complexes with Neutral N3 Donor Ligands". Organometallics. 24 (13): 3136–3148. doi:10.1021/om050209r.
7. "Tricarbonyl 1,3,5‐Trimethyl‐1,3,5‐Triazacyclohexane Complexes of Chromium(0), Molybdenum(0), and Tungsten(0) M(CO)₃(Me₃TACH) (M = Cr, Mo, W)]". Inorganic Syntheses. 35: 109. 2010. doi:10.1002/9780470651568.ch6.