Tris(2-aminoethyl)amine at a Glance
Tris(2-aminoethyl)amine, almost always written TREN, is a tetraamine with CAS number 4097-89-6 and formula C6H18N4 (MW 146.23). Three 2-aminoethyl arms are attached to a single nitrogen atom, which makes the molecule a pre-organised tetradentate ligand, a fast self-catalysing epoxy hardener, and one of the polyamines studied for CO2 absorption.
Its commercial identity is defined by an awkward coincidence: TREN is an isomer of triethylenetetramine (TETA, CAS 112-24-3). Both are C6H18N4 at 146.2 g/mol, both carry six active hydrogens, both have an amine equivalent weight of 24.4 g/eq – and both are sold as "tetraamine". Yet one is branched around a tertiary nitrogen and the other is a linear chain with a secondary nitrogen, and that difference decides cure speed, chelate geometry and CO2 loading. Any buyer who compares them on price per tonne without comparing on isomer has compared nothing.
PolyBlueChem supplies TREN at 98.0% min by GC with 0.5% max water; this article covers the chemistry, the manufacturing logic, the specifications that actually predict performance, and the selection rules against the other ethyleneamines.
Chemical and Physical Profile
| Property | Value | Note |
|---|---|---|
| CAS number | 4097-89-6 | – |
| Synonyms | TREN; tris(2-aminoethyl)amine; 2,2′,2”-nitrilotriethylamine; N,N-bis(2-aminoethyl)ethane-1,2-diamine | Also sold as the "tren" ligand in coordination chemistry |
| Formula | C6H18N4 | – |
| Molecular weight | 146.23 g/mol | PubChem CID 77731 |
| SMILES | NCCN(CCN)CCN | Three primary amines plus one tertiary amine |
| Appearance | Pale yellow to colourless liquid | Darkening is an ageing indicator |
| Nitrogen content | 38.3% (calculated) | 4 x 14.007 / 146.23 |
| Amine functionality | 3 primary (6 N-H) + 1 tertiary | The tertiary nitrogen is why the molecule self-catalyses |
| Amine equivalent weight | 24.4 g/eq (calculated) | 146.23 / 6 – the number used for epoxy stoichiometry |
| Water solubility | Fully miscible | Strongly hygroscopic in the drum as well |
| Computed lipophilicity (XLogP) | -2.6 | PubChem computed value; strongly hydrophilic |
| Computed polar surface area | 81.3 Å2 | PubChem computed value |
| Reactivity | Strong base; absorbs CO2; attacks copper and aluminium | See storage section |
Two practical notes. First, the calculated nitrogen content and amine equivalent weight are the two figures a buyer should be able to reproduce from the formula – if a supplier’s COA cannot be reconciled with them, ask what else is in the drum. Second, the material has no meaningful vapour pressure at ambient conditions, but it is corrosive as a liquid and as a mist, and its amine smell is not a reliable guide to concentration.
How Tris(2-Aminoethyl)amine Is Made
TREN is a speciality cut inside the ethyleneamine family, not a bulk commodity like EDA, DETA or TETA. The reported commercial routes fall into two families:
- Alkylation of ammonia or ethylenediamine with a 2-haloethylamine, classically as the hydrochloride, followed by neutralisation and distillation. This is the textbook route and the one most often used for speciality and small-volume production, because the branching is built in by the alkylation pattern rather than separated afterwards.
- Catalytic amination and reductive amination of ethanolamine- or glyoxal-derived intermediates over nickel or cobalt catalysts, which is the same technology family that produces the mainstream ethyleneamines. Here TREN appears in the polyamine cut together with TETA and higher oligomers.
Either way the crude product is a mixture of linear and branched tetraamines, and the difference between a 98% TREN and a "tetraamine, 98%" is whether that mixture has been fractionated. This is the reason TREN trades at a multiple of TETA’s price despite identical formula and identical molecular weight: you are paying for the distillation that separates the branched isomer from its linear twin. A supplier who cannot state which isomer the assay refers to has not specified the product.
Two process consequences matter downstream:
- Residual linear polyamine shows up as slower-than-expected cure in epoxy systems and as a different chelate stability constant in ligand work.
- Colour is a better ageing indicator than purity for this product. Amines oxidise and pick up CO2; a batch that is inside the GC specification but noticeably darker than the previous one has been exposed.
Grades and Specifications
The standard commercial specification for distilled TREN is short – which is normal for a speciality amine:
| Property | Standard specification | Why it is on the sheet |
|---|---|---|
| Appearance | Pale yellow to colourless liquid | Ageing and CO2 pickup indicator |
| Purity (GC) | 98.0% min | Distilled product; the balance is mainly linear tetraamine and higher oligomers |
| Moisture (Karl Fischer) | 0.5% max | Hygroscopic; water travels with CO2 pickup |
| Nitrogen content | 38.3% theoretical | Cross-check on assay |
| Amine equivalent weight | 24.4 g/eq theoretical | Cross-check on functionality |
Buyers with a sensitive application usually add two more requirements: an isomer distribution (branched vs linear tetraamine) and a colour limit (Gardner or APHA). Both are worth writing into the purchase specification rather than discovering at the bench, because neither is captured by a GC purity figure alone.
Application Overview
| Application | Function of TREN | What the formulation actually buys |
|---|---|---|
| Epoxy coatings, adhesives, composites | Hardener / chain extender, 6 active H | Fast cure and self-acceleration from the tertiary nitrogen |
| Chelating agents and chelating polymers | Tetradentate N4 ligand | One-to-one metal binding with a pre-organised pocket |
| Metal treatment and catalyst precursors | Ligand for Cu, Zn, Ni complexes | Defined coordination geometry; water-soluble complexes |
| Gas treating / CO2 capture | Primary amine absorbent | High amine density per unit mass; three reactive sites per molecule |
| Dendrimers and hyperbranched polymers | Branch point (PAMAM-type cores) | Three arms from one nitrogen in a single step |
| Surfactants, lubricant additives, asphalt emulsifiers | Multifunctional amine head group | Multiple anchoring points per molecule |
Epoxy Curing: Stoichiometry and Self-Catalysis
The stoichiometric hardener weight per 100 g of resin is calculated from the amine equivalent weight and the epoxy equivalent weight of the resin:
phr = (amine equivalent weight x 100) / epoxy equivalent weight
| Resin EEW | TREN phr (stoichiometric) | Comment |
|---|---|---|
| 185 (low-viscosity liquid DGEBA) | 13.2 | Typical room-temperature coating or adhesive |
| 190 | 12.8 | – |
| 250 | 9.8 | Semi-solid resin; often blended before cure |
| 500 (solid grade) | 4.9 | Powder or solution systems |
Note what this table says: on a stoichiometric basis TREN and TETA are interchangeable to the gram, and yet they cure differently, because the tertiary nitrogen in TREN accelerates the epoxy-amine reaction while the secondary nitrogen in TETA does not. In practice that means:
- Shorter gel time at the same loading, which is an advantage in thin films and low-temperature cure and a liability in large pours where exotherm and pot life matter.
- Less need for an external accelerator, so the formulation is simpler – but harder to slow down, since the catalyst is built into the hardener.
- More colour and more exotherm sensitivity: fast cures run hotter, and hot cures yellow more. If colour is critical, cure at lower temperature with a longer schedule rather than reducing hardener below stoichiometry.
The most common mistake with TREN in epoxy work is under-dosing to buy pot life. Below stoichiometry the film never reaches full crosslink density, and the failure shows up months later as poor chemical resistance rather than as a tacky film on day one.
Chelation: Tetradentate Behaviour and Metal Ratios
TREN is one of the classic tetradentate N4 ligands: the three primary arms and the central tertiary nitrogen all coordinate, so a single molecule wraps a metal ion and occupies four coordination sites. For divalent Cu, Zn or Ni this normally gives a 1:1 complex with the remaining sites filled by water or a co-ligand.
| Metal ion | Complex stoichiometry | TREN required per kg of metal |
|---|---|---|
| Cu(II) | 1:1 | 2.30 kg |
| Zn(II) | 1:1 | 2.24 kg |
| Ni(II) | 1:1 | 2.49 kg |
These figures are calculated from 146.23 g/mol of TREN against the atomic weight of each metal, and they are the right way to cost a chelation application: cost per kg of metal chelated, not cost per kg of ligand. The same arithmetic applied to a polymeric chelating resin or an EDDHA-type micronutrient explains why small-molecule polyamines are used where a soluble, well-defined complex is wanted rather than a slow-release one.
Practical notes for chelate work: complexation is fast at ambient temperature and best run with the metal salt in water, adding TREN with cooling because the reaction is exothermic; the free ligand is strongly basic, so the pH of the finished solution is set by the metal complex rather than by the ligand, and strong acid must be avoided or the ligand is simply protonated and stops coordinating.
CO2 Capture and Gas Treating
Each TREN molecule carries three primary amines, so the theoretical CO2 capacity depends on which chemistry dominates:
| Pathway | Amines per CO2 | CO2 per molecule | Mass loading (g CO2 per g TREN) |
|---|---|---|---|
| Carbamate (two amines per CO2) | 2 | 1.5 | 0.45 |
| Bicarbonate / carbonate (one amine per CO2) | 1 | 3 | 0.90 |
The carbamate pathway is the one that governs in water-lean or non-aqueous amine systems; the bicarbonate pathway requires enough water for hydrolysis and is the theoretical ceiling, not a working number. What makes TREN interesting in the CO2 literature is not the raw capacity – it is the combination of a high amine density per unit mass with a molecule that resists the thermal degradation that hits more heavily substituted amines. What makes it difficult is the same property that sells it elsewhere: viscosity rise and precipitation on loading, because carbamate salts of polyamines are not always soluble in their own solution. Any gas-treating evaluation should therefore measure loaded viscosity, not just capacity.
TREN vs Other Ethyleneamines
| Product | CAS | Formula / MW | Active H | Amine eq. wt | Positioning |
|---|---|---|---|---|---|
| TREN | 4097-89-6 | C6H18N4 / 146.23 | 6 | 24.4 | Branched, self-catalysing, tetradentate – speciality |
| TETA | 112-24-3 | C6H18N4 / 146.24 | 6 | 24.4 | Linear isomer, bulk commodity hardener |
| DETA | 111-40-0 | C4H13N3 / 103.17 | 5 | 20.6 | Lower viscosity and lower equivalent weight; faster, more exotherm |
| EDA | 107-15-3 | C2H8N2 / 60.10 | 4 | 15.0 | Shortest chain, highest reactivity and hazard |
| AEEA | 111-41-1 | C4H12N2O / 104.15 | 3 | 34.7 | Hydroxyl plus amine; slower, better flexibility |
Read the table by column, not by row. On equivalent weight TREN and TETA are identical; on isomer they are opposites. Choose TREN when you need the branched geometry or the built-in catalysis and can justify a speciality price. Choose TETA when you need tonnage and a known cure schedule. Choose DETA when you need a lower-viscosity hardener and can accept a faster, hotter reaction.
Procurement Guide
| Decision | What to specify |
|---|---|
| Grade | 98.0% min by GC, and the isomer basis of that assay |
| Water | 0.5% max by Karl Fischer |
| Colour | Gardner or APHA limit if the application is colour-sensitive |
| Packaging | 1 kg / 5 kg / 25 kg for development; 200 kg drum for production – nitrogen-blanketed |
| Documentation | COA per batch, current SDS, and any declaration your market requires (for example non-GMO or origin statements for pharma-adjacent uses) |
| Price basis | Per kg of TREN, delivered; not per kg of "tetraamine" |
Three questions separate a real TREN offer from a relabelled TETA cut: what is the isomer distribution, what is the water figure, and what is the colour of the current batch. A supplier who answers all three without asking why is selling a distilled product; one who answers only the first is selling a cut.
Safety, Handling and Regulatory Position
- Hazard profile: corrosive to skin and eyes (severe burns, serious eye damage), harmful if inhaled or swallowed, may cause an allergic skin reaction. Treat as a corrosive amine, not as a solvent.
- Nitrosamine precursor: TREN is a tertiary amine. Do not let it contact nitrites or nitrosating agents, and do not combine the two in cleaning or waste streams – the handling discipline for this class exists precisely because of nitrosamine formation.
- Materials of construction: stainless steel, HDPE and PTFE are suitable; copper, brass and aluminium are attacked. Amine-resistant gaskets and hoses matter as much as the tank.
- Storage: sealed, dry, ventilated, away from acids and oxidisers. Nitrogen blanketing is the single most effective protection against the CO2 pickup that degrades the product.
- Regulatory position: TREN is an industrial amine, not a narcotic, precursor-controlled or drug substance. It is not on the main export-control lists for this product category; buyers remain responsible for their own local registration and end-use declarations, and for confirming duties and documentation at destination.
Frequently Asked Questions
Is TREN the same product as TETA?
No. Both are C6H18N4 at 146.2 g/mol with an amine equivalent weight of 24.4 g/eq, but TREN is the branched isomer (three arms on a tertiary nitrogen) and TETA is the linear isomer (secondary nitrogen in the chain). They are interchangeable on stoichiometry, not on cure speed, pot life or chelate geometry.
Why is TREN more expensive than TETA?
Because it is a distilled speciality cut, not a bulk cut. The branched isomer has to be separated from the linear tetraamine produced alongside it, and the volumes traded are orders of magnitude smaller. You are paying for fractionation, not for a different formula.
How much TREN do I need for a given epoxy resin?
phr = 24.4 x 100 / EEW. For a standard liquid DGEBA at EEW 185 that is 13.2 phr. Because TREN self-accelerates, keep the loading at stoichiometry and control cure rate with temperature rather than by cutting hardener.
Does TREN absorb CO2 in storage?
Yes, readily, and that is the main degradation pathway. Carbamates and carbonates form, the liquid hazes or darkens and the active amine content falls. Keep drums sealed and nitrogen-blanketed, and check water and colour on receipt rather than trusting the GC assay alone.
Can you supply small quantities for development work?
Yes – 1 kg and 5 kg packs are standard for this product alongside 25 kg jerricans and 200 kg drums, each with a batch COA and the current SDS.
References and Disclaimer
- PubChem CID 77731 – molecular formula, molecular weight, SMILES and computed properties for tris(2-aminoethyl)amine.
- CAS registry numbers for the comparison products (TETA 112-24-3, DETA 111-40-0, EDA 107-15-3, AEEA 111-41-1) as listed in standard supplier catalogues.
- Amine equivalent weights in this article are calculated from molecular weight and active hydrogen count; epoxy phr values are calculated, not measured, and must be confirmed against the specific resin and cure schedule.
Disclaimer: this article is technical and commercial information for industrial buyers. It is not a specification, a safety data sheet or a substitute for either. Handle tris(2-aminoethyl)amine according to the supplier’s current SDS and your local regulations.
PolyBlueChem supplies tris(2-aminoethyl)amine (TREN, CAS 4097-89-6) at 98.0% min GC, water 0.5% max, in 1 kg to 200 kg packs with per-batch COA and SDS. Send us the application – epoxy curing, chelation or gas treating – and we will confirm the grade, the isomer basis of the assay and the documentation you need. View the TREN product page for the current specification, or contact us for a quotation against your required pack size.