Triisopropylamine

Triisopropylamine

Names
Preferred IUPAC name N,N-Di(propan-2-yl)propan-2-amine
Other names Tri(propan-2-yl)amine (Triisopropyl)amine
Identifiers
CAS Number	3424-21-3
3D model (Jmol)	Interactive image
ChemSpider	55785
ECHA InfoCard	100.020.289
EC Number	222-317-5
PubChem	61924
UNII	Y67CF9Z56L
InChI InChI=1S/C9H21N/c1-7(2)10(8(3)4)9(5)6/h7-9H,1-6H3 Key: RKBCYCFRFCNLTO-UHFFFAOYSA-N
SMILES CC(C)N(C(C)C)C(C)C
Properties
Chemical formula	C9H21N
Molar mass	143.27 g·mol^−1
Appearance	Colorless liquid
Odor	Ichtyal, ammoniacal
Density	0.752 g/cm^3
Boiling point	47 °C (117 °F; 320 K) at 1.9 kPa
Related compounds
Related amines	Dimethylamine Trimethylamine N-Nitrosodimethylamine Diethylamine Triethylamine Diisopropylamine Dimethylaminopropylamine Diethylenetriamine N,N-Diisopropylethylamine Tris(2-aminoethyl)amine Mechlorethamine HN1 (nitrogen mustard) HN3 (nitrogen mustard)
Related compounds	Unsymmetrical dimethylhydrazine Biguanide Dithiobiuret Agmatine
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

Triisopropylamine is an organic chemical compound consisting of three isopropyl groups bound to a central nitrogen atom.^[1][2] As a hindered tertiary amine, it can be used as a non-nucleophilic base and as a stabilizer for polymers; however, its applications are limited by its relatively high cost and difficult synthesis.

Structure

Triisopropylamine is notable as being the most sterically crowded amine currently known. The even more crowded tri-tert-butyl-amine (^tBu₃N) has never been successfully synthesized, although the existence of 2,2,4,4-Tetramethyl-3-t-butyl-pentane-3-ol (^tBu₃COH) implies that it may be possible.

In the early 1990s, theoretical studies and electron diffraction analysis of the 3D structure of the molecule, in the gas phase or in non-polar solvents, indicated that the bonds between the nitrogen atom and the three carbon atoms were nearly coplanar in the ground state, instead of forming a trigonal pyramid as in simpler amines.^[3][4] The average C-N-C angle was claimed to be 119.2°,^[2] much closer to the 120° of the flat configuration than to the 111.8° of trimethylamine. This peculiarity was attributed to steric hindrance by the bulky isopropyl radicals. However, in 1998 X-ray diffraction analysis of the crystallized solid showed that the C₃N core is actually pyramidal, with the N atom lying approximately 0.28 Å off the carbons' plane (whereas in trimethylamine the distance is about 0.45 Å). However the researchers could not rule out the crystal field effect as the cause of the asymmetry.^[5]

The C-C-C planes of the isopropyl groups are slightly tilted (about 5°) relative to the threefold symmetry axis of the C₃N core.^[3][5][6]

Preparation

Steric effects make triisopropylamine difficult to synthesise and unlike less hindered tertiary amines (such as triethylamine) it cannot be produced by the alkylation of ammonia with alcohol; attempts to do so stall at diisopropylamine. It can be prepared from diisopropylamine by a procedure developed by Bock and others:^[2]

References

1. G. Graner, E. Hirota, T. Iijima, K. Kuchitsu, D. A. Ramsay, J. Vogt and N. Vogt (2003), C9H21N, Triisopropylamine. In Molecules Containing Five or More Carbon Atoms, volume 25D of the series Landolt-Börnstein - Group II Molecules and Radicals. Springer-Verlag. ISBN 978-3-540-42860-2; DOI 10.1007/10735542_789.
2. Hans Bock; Ilka Goebel; Zdenek Havlas; Siegfried Liedle; Heinz Oberhammer (1991). "Triisopropylamine: A Sterically Overcrowded Molecule with a Flattened NC3 Pyramid and a "p-Type" Nitrogen Electron Pair". Angew. Chem. Int. Ed. 30 (2): 187–190. doi:10.1002/anie.199101871.
3. Arthur M. Halpern; B. R. Ramachandran (1992). "Photophysics of a sterically crowded tertiary-saturated amine: triisopropylamine". J. Phys. Chem. 96 (24): 9832–9839. doi:10.1021/j100203a047.
4. Christoph Kölmel, Christian Ochsenfeld & Reinhart Ahlrichs (1992). "An ab initio investigation of structure and inversion barrier of triisopropylamine and related amines and phosphines". Theoretical Chemistry Accounts: Theory, Computation, and Modeling (Theoretica Chimica Acta). 82 (3–4).
5. Boese, R.; Bläser, D.; Antipin, M. Y.; Chaplinski, V.; de Meijere, A. (1998). "Non-planar structures of Et3N and Pri3N: a contradiction between the X-ray, and NMR and electron diffraction data for Pri3N". Chem. Commun. (7): 781–782. doi:10.1039/a708399h.
6. Yang M, Albrecht-Schmitt T, Cammarata V, Livant P, Makhanu DS, Sykora R, Zhu W (2009). "Trialkylamines more planar at nitrogen than triisopropylamine in the solid state". J. Org. Chem. 74 (7): 2671–8. doi:10.1021/jo802086h. PMID 19323571.