Triisopropylamine is an organic

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

consisting of three

isopropyl In organic chemistry, propyl is a three-carbon alkyl substituent with chemical formula for the linear form. This substituent form is obtained by removing one hydrogen atom attached to the terminal carbon of propane. A propyl substituent is ofte ...

groups bound to a central

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

atom Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons. Every solid, liquid, gas, and ...

. As a hindered

tertiary amine In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituent such a ...

, it can be used as a

non-nucleophilic base As the name suggests, a non-nucleophilic base is a sterically hindered organic base that is a poor nucleophile. Normal bases are also nucleophiles, but often chemists seek the proton-removing ability of a base without any other functions. Typic ...

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 among the most sterically hindered amines currently known. The even more crowded tri-''tert''-butylamine (^''t''Bu₃N) has never been synthesized, although ''ab initio'' quantum chemical computations as well as the existence of the even more crowded 2,2,4,4-tetramethyl-3-''t''-butyl-pentane-3-ol (tri-''tert''-butylcarbinol, ^''t''Bu₃COH) implies that it should be a stable molecule if it could be prepared. To date, di-''tert''-butyl(isopropyl)amine (^''t''Bu₂ⁱPrN) has been prepared in low yield, as have a handful of tri-''tert''-alkylamines in which two of the ''tert''-alkyl groups are tied together in a ring, but the authors of a 2018 study predict that ^''t''Bu₃N will likely remain a longstanding unsolved synthetic challenge. In the early 1990s, theoretical studies and

electron diffraction Electron diffraction refers to the bending of electron beams around atomic structures. This behaviour, typical for waves, is applicable to electrons due to the wave–particle duality stating that electrons behave as both particles and waves. Si ...

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 Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...

atoms were nearly coplanar in the ground state, instead of forming a

trigonal pyramid In geometry, a pyramid () is a polyhedron formed by connecting a polygonal base and a point, called the apex (geometry), apex. Each base edge and apex form a triangle, called a ''lateral face''. It is a cone, conic solid with polygonal base. A ...

as in simpler amines. The average C-N-C angle was claimed to be 119.2°, much closer to the 120° of the flat configuration than to the 111.8° of

trimethylamine Trimethylamine (TMA) is an organic compound with the formula N(CH3)3. It is a colorless, hygroscopic, and flammable tertiary amine. It is a gas at room temperature but is usually sold as a 40% solution in water. (It is also sold in pressurized ...

. This peculiarity was attributed to

steric hindrance Steric effects arise from the spatial arrangement of atoms. When atoms come close together there is a rise in the energy of the molecule. Steric effects are nonbonding interactions that influence the shape ( conformation) and reactivity of ions ...

by the bulky isopropyl radicals. However, in 1998

X-ray diffraction X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles ...

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

Preparation

Steric effects Steric effects arise from the spatial arrangement of atoms. When atoms come close together there is a rise in the energy of the molecule. Steric effects are nonbonding interactions that influence the shape ( conformation) and reactivity of ions ...

make triisopropylamine difficult to synthesise and unlike less hindered

s (such as

triethylamine Triethylamine is the chemical compound with the formula N(CH2CH3)3, commonly abbreviated Et3N. It is also abbreviated TEA, yet this abbreviation must be used carefully to avoid confusion with triethanolamine or tetraethylammonium, for which TEA ...

) it cannot be produced by the

alkylation Alkylation is the transfer of an alkyl group from one molecule to another. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene (or their equivalents). Alkylating agents are reagents for effecting ...

of ammonia with alcohol; attempts to do so stall at diisopropylamine. It can be prepared from diisopropylamine on the laboratory scale: : Preparation of triisopropylamine

Industrial synthesis involves the reaction of

ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous was ...

with

propylene oxide Propylene oxide is an acutely toxic and carcinogenic organic compound with the molecular formula CH3CHCH2O. This colourless volatile liquid with an odour similar to ether, is produced on a large scale industrially. Its major application is its us ...

followed by hydrogenation.

References

{{reflist Non-nucleophilic bases Diisopropylamino compounds Tertiary amines

Structure

Preparation

See also

References