1. Glutaraldehyde (CAS 111-30-8): An Overview
Glutaraldehyde (CAS 111-30-8), also known as pentanedial or 1,5-pentanedial, is a five-carbon dialdehyde with two terminal aldehyde groups. It is one of the most important industrial dialdehydes, valued for two properties: its powerful, broad-spectrum antimicrobial activity and its ability to crosslink proteins, polymers and other nucleophilic substrates. Those two properties make it a workhorse in industrial water treatment, oilfield operations, leather tanning, medical device disinfection and biotechnology.
Although the pure compound is a colourless, pungent liquid, it is unstable in that form and is almost always supplied and used as an aqueous solution, typically at 25% or 50% (w/w). The behaviour of those solutions – which contain a mixture of hydrated, cyclic and polymeric species rather than a single free dialdehyde – is the single most important thing to understand about the material, and it is covered in Section 3.
This article reviews the chemistry, solution behaviour, manufacturing routes, specifications, applications and handling of glutaraldehyde from the perspective of a supplier and industrial user.
2. Chemical Identity and Physicochemical Properties
| Property | Value |
|---|---|
| Chemical name (IUPAC) | Pentanedial (glutaraldehyde) |
| Common names | Glutaraldehyde; glutaral; 1,5-pentanedial; glutardialdehyde |
| CAS Registry Number | 111-30-8 |
| Molecular formula | C5H8O2 |
| Molecular weight | 100.12 g/mol |
| Structure | OHC-CH2-CH2-CH2-CHO (two terminal aldehyde groups) |
| Pure compound | Colourless to pale yellow, pungent liquid; unstable, so rarely handled in pure form |
| Commercial form | Aqueous solution, typically 25% or 50% (w/w) |
| Solubility | Miscible with water and with many polar organic solvents |
| Typical solution pH | Acidic (about pH 3-4) as supplied, for stability |
| PubChem CID | 3485 |
The molecular symmetry of glutaraldehyde – two identical aldehyde groups at opposite ends of a flexible three-carbon bridge – is the origin of its crosslinking ability. When the two aldehyde ends react with nucleophiles on two different molecules (for example, lysine residues on two different proteins), the result is a covalent bridge that ties the two molecules together.
3. Aqueous Solution Chemistry: The Key to Understanding Glutaraldehyde
The most common mistake when working with glutaraldehyde is to assume that a 25% solution contains 25% of the free dialdehyde. In practice, commercial solutions are a complex equilibrium mixture, and the distribution of species depends strongly on pH, concentration and temperature.
In water, the free dialdehyde exists only in small amounts. The aldehyde groups are hydrated to gem-diols, and the molecule readily folds into a cyclic hemiacetal in which one aldehyde carbon is attacked by an oxygen of the other hydrated end to form a six-membered ring. This cyclic form is the predominant species in the acidic, as-supplied solutions. Under certain conditions, particularly at higher pH and concentration, the molecules also react with one another to form oligomeric and polymeric alpha,beta-unsaturated species.
| Species in solution | Description | Favoured conditions |
|---|---|---|
| Free dialdehyde (monomer) | Reactive OHC-(CH2)3-CHO form | Present in small equilibrium amounts; increases under certain conditions |
| gem-Diol (hydrate) | Both aldehyde ends hydrated | Dilute aqueous solution |
| Cyclic hemiacetal | Intramolecular ring form; the dominant species in acidic solution | Acidic pH (about 3-4), the as-supplied state |
| Oligomers / polymers | Higher-molecular-weight condensation products | Higher pH, higher concentration, ageing |
The practical consequences are important:
- Stability. Commercial solutions are deliberately kept acidic (about pH 3-4) to suppress polymerization and to preserve the distribution of species, which is why they store far longer at acidic pH.
- Activation. Raising the pH towards neutral or slightly alkaline – the classic “activation” step with a buffer such as sodium bicarbonate – shifts the equilibrium and generates the more reactive species responsible for antimicrobial action. Activated solutions are less stable, which is why they are prepared shortly before use.
- Measured concentration. Because most of the aldehyde is tied up in hydrated and cyclic forms, the “assay” of a glutaraldehyde solution reflects total dialdehyde, not free monomer. This is why titration, rather than a simple free-aldehyde measurement, is used for specification.
4. Mechanism of Antimicrobial Action
Glutaraldehyde is a broad-spectrum antimicrobial agent active against bacteria (including many that form biofilms), fungi, algae and viruses. Its action is a crosslinking reaction rather than a simple toxic effect.
The aldehyde groups react with nucleophilic groups on microbial cell surfaces and within the cell – principally the amino groups of proteins and the residues of nucleic acids. Because glutaraldehyde is bifunctional, it can bridge two nucleophiles, forming a crosslinked, denatured network that disrupts the cell wall, the cell membrane and essential enzyme function. Immobilised, crosslinked proteins cannot carry out their normal catalytic and structural roles, so the cell dies.
Two features make this mechanism practically useful. First, because it targets structural proteins and does not depend on a single metabolic pathway, resistance is rare. Second, the same chemistry that kills microbes is what makes glutaraldehyde a useful protein crosslinker in industrial and biotechnological processes.
Because the reactive species are generated as the pH is raised, the antimicrobial performance of a glutaraldehyde solution is closely tied to its use pH – a point that connects directly to the activation behaviour described in Section 3.
5. Manufacturing Routes: The Acrolein-Based Synthesis
Industrial glutaraldehyde is produced almost entirely from acrolein (prop-2-enal). The central transformation is a reaction between acrolein and a vinyl ether or an alcohol to give a substituted dihydropyran, which is then hydrolysed to glutaraldehyde.
Route A: Acrolein + vinyl ether (the principal commercial route)
Acrolein reacts with a vinyl ether such as vinyl ethyl ether in a cycloaddition-type reaction to give 2-ethoxy-3,4-dihydro-2H-pyran. Acid-catalysed hydrolysis of this intermediate cleaves the ring and the ether to release glutaraldehyde together with the parent alcohol (ethanol in this case):
CH2=CH-CHO + CH2=CH-OEt → 2-ethoxy-3,4-dihydro-2H-pyran → OHC-(CH2)3-CHO + EtOH
Route B: Acrolein + alcohol
A closely related route uses an alcohol such as methanol in place of the vinyl ether, giving 2-methoxy-3,4-dihydro-2H-pyran as the intermediate, which is likewise hydrolysed to glutaraldehyde and methanol. Methanol can be recovered and recycled, which is one reason this variant is attractive.
Other routes
Older and lower-volume routes start from different feedstocks – for example, oxidation of 1,5-pentanediol, oxidation of cyclopentene, or reductive routes from glutaric acid derivatives. These are of limited commercial importance because the acrolein-based chemistry is more atom-efficient and better suited to large-scale operation.
| Route | Key raw materials | Key intermediate | Status |
|---|---|---|---|
| Acrolein + vinyl ether | Acrolein, vinyl ethyl ether | 2-Ethoxy-3,4-dihydro-2H-pyran | Principal commercial route |
| Acrolein + alcohol | Acrolein, methanol | 2-Methoxy-3,4-dihydro-2H-pyran | Commercial; alcohol recyclable |
| 1,5-Pentanediol oxidation | 1,5-Pentanediol, air/O2 | None (direct oxidation) | Older / niche |
| Cyclopentene or glutaric acid routes | Cyclopentene / glutaric acid derivatives | Various | Research / niche |
Whatever the route, the product leaving the reactor is an aqueous glutaraldehyde solution that is then concentrated, adjusted in pH and formulated to the specified strength. Because acrolein is a highly reactive and hazardous intermediate, acrolein-based plants require careful engineering and containment.
6. Grades and Specifications
Glutaraldehyde is sold as an aqueous solution rather than as a purified solid. The two standard strengths are 25% and 50% (w/w), with 50% being the form usually bought in bulk by formulators and 25% (or further-diluted) solutions being common in end-use products.
| Parameter | Typical specification |
|---|---|
| Appearance | Clear, colourless to pale yellow liquid |
| Assay (total dialdehyde) | Typically 25% or 50% (w/w), as agreed |
| pH (as supplied) | Acidic, typically about pH 3-4 |
| Odour | Pungent, characteristic aldehyde odour |
| Miscibility | Fully miscible with water |
Because the specification is expressed as total dialdehyde, buyers should confirm both the nominal strength and the analytical method used, and should note the pH at which the material is supplied, since pH has a direct effect on stability and on the species distribution in solution.
7. Activation and Use of Glutaraldehyde Solutions
Glutaraldehyde is supplied in a relatively unreactive, acidic form and is “activated” when it is to be used for antimicrobial purposes. Activation is normally achieved by raising the pH to about 7.5-8.5 with an alkaline buffer, most commonly sodium bicarbonate.
Two practical points follow from this. First, activated solutions have a limited working life and are normally prepared shortly before use and discarded after the recommended period. Second, activation is a formulation step, not a change in the product: the same 25% or 50% stock solution is simply adjusted in pH at the point of use. Industrial users therefore buy the acidic stock solution and carry out activation in their own process, which is why the acidic, stable form is the standard article of commerce.
8. Applications: Industrial Water Treatment and Oilfield
The largest industrial use of glutaraldehyde is as a non-oxidising biocide in water systems, where it controls bacteria, algae and fungi that would otherwise foul equipment or corrode metal surfaces.
| Sector | Application | Typical role |
|---|---|---|
| Cooling water systems | Biological control in cooling towers and recirculating systems | Non-oxidising biocide, often used in alternating programmes with oxidising biocides |
| Oilfield / produced water | Sulphate-reducing and general bacterial control in injection and process water | Biocide to prevent souring and microbially influenced corrosion |
| Pulp and paper mills | Control of slime-forming organisms in process water | Biocide/slimicide |
| General industrial water | Preservation and disinfection of process water | Broad-spectrum biocide |
In these systems glutaraldehyde is frequently used in rotation with other biocides to manage cost and to minimise the development of tolerance, and it is often formulated with surfactants or other actives to improve performance.
9. Applications: Leather Tanning and Textiles
In leather making, glutaraldehyde is a well-established tanning and re-tanning agent. Its aldehyde groups react with the amino groups of the collagen protein in the hide, crosslinking the fibre structure and converting the raw hide into stable leather. Glutaraldehyde tanning is valued as a chromium-free, aldehyde-based approach that gives soft, full leather with good resistance to heat and moisture, and it is often combined with other tanning agents in modern formulations.
In textiles, glutaraldehyde is used as a crosslinking and finishing agent – for example, in durable-press and wrinkle-resistant finishing, and as a component of low- or non-formaldehyde finishing systems where its reactivity is used to bond finishes to cellulose fibres. Its ability to form stable covalent links with fibre-bound nucleophiles is the basis of these uses.
10. Applications: Crosslinking and Biotechnology
Glutaraldehyde’s second major role is as a protein and polymer crosslinker, which arises from exactly the same chemistry that makes it an antimicrobial.
- Protein and enzyme immobilisation. Glutaraldehyde is used to crosslink enzymes and proteins onto supports, stabilising them for use in biocatalysis, biosensors and industrial processes.
- Fixation of biological specimens. In microscopy and histology, glutaraldehyde is a standard fixative that crosslinks tissue proteins and preserves structure for examination. This is a laboratory application and is distinct from any clinical use.
- Biopolymer and hydrogel crosslinking. It is used to crosslink gelatin, collagen, chitosan and other biopolymers to tune the mechanical and stability properties of films, scaffolds and hydrogels.
- Industrial polymer and coating crosslinking. Glutaraldehyde is used to crosslink polymers and to improve the performance of certain adhesives, coatings and resins.
11. Handling, Safety and Storage
Glutaraldehyde is a reactive dialdehyde and a potent sensitiser, and it must be handled with appropriate controls. Even at the concentrations used industrially, the vapour and the liquid can irritate the eyes, skin and respiratory tract, and repeated exposure can lead to sensitisation.
- Engineering controls. Use local exhaust ventilation or closed systems, and avoid generating mists or aerosols; the characteristic pungent odour is a useful warning signal but is not a safe indicator of concentration.
- Personal protective equipment. Chemical-resistant gloves, eye/face protection and suitable respiratory protection should be used where vapour or aerosol exposure is possible.
- Storage. Keep the solution in closed, clearly labelled containers, protected from heat and contamination, and store at the acidic pH at which it is supplied. Do not store activated solutions for long periods.
- Disposal. Glutaraldehyde waste and spent activated solutions must be managed according to local regulations and should not be discharged untreated.
The safety data sheet (SDS) should be consulted for full hazard, first-aid and transport information, and local occupational and environmental regulations should be observed.
12. Procurement: Packaging, Documentation and Selection
| Consideration | What to confirm |
|---|---|
| Strength | 25% or 50% (w/w) total dialdehyde, as required by your formulation |
| Assay method | The analytical method used, since the specification is total rather than free aldehyde |
| pH as supplied | Acidic (typically about pH 3-4); confirm it suits your activation step |
| Appearance | Clear, colourless to pale yellow liquid |
| Packaging | Jerricans, drums or IBCs as agreed; sealed to limit vapour exposure |
| Documentation | Certificate of Analysis (COA) and SDS; additional documents on request |
| Storage and shelf life | Cool, closed storage at the supplied acidic pH; retest period per COA |
Because glutaraldehyde is supplied and used as a solution, the practical quality questions are about strength, pH and stability rather than about a solid form. A clear COA covering assay and pH, together with a current SDS, is the minimum documentation package for industrial buyers.
13. Frequently Asked Questions
What is glutaraldehyde and what is it used for?
Glutaraldehyde (CAS 111-30-8, C5H8O2) is a five-carbon dialdehyde. Its main uses are as a non-oxidising biocide in industrial water and oilfield systems, as a crosslinking agent in leather tanning and textiles, and as a protein crosslinker in biotechnology.
Is glutaraldehyde a pure dialdehyde in solution?
No. In water, most of the glutaraldehyde is present as hydrated and cyclic hemiacetal species, with only a small amount as the free dialdehyde. This is why the specification is expressed as total dialdehyde and why pH has such a strong effect on behaviour.
Why is glutaraldehyde supplied at acidic pH?
Acidic conditions (about pH 3-4) favour the stable cyclic hemiacetal form and suppress polymerization, so the solution stores well at that pH. Raising the pH to activate the solution for use also makes it less stable.
What is “activated” glutaraldehyde?
Activated glutaraldehyde is a solution whose pH has been raised – typically to about 7.5-8.5 with an alkaline buffer such as sodium bicarbonate – to generate the more reactive species needed for antimicrobial action. Activated solutions are prepared shortly before use.
How is glutaraldehyde made industrially?
It is produced mainly from acrolein, which reacts with a vinyl ether or an alcohol to give a substituted dihydropyran that is then hydrolysed to glutaraldehyde. Oxidation of 1,5-pentanediol and other routes exist but are of minor commercial importance.
What concentrations are available?
Glutaraldehyde is normally supplied as a 25% or 50% (w/w) aqueous solution; the 50% grade is common in bulk and formulations for end use are often more dilute.
Why is glutaraldehyde used instead of oxidising biocides?
Glutaraldehyde is a non-oxidising biocide, so it is not consumed by oxidisable matter in the system in the way an oxidising biocide is. This makes it useful in rotation with oxidising biocides and in systems where oxidising chemistry is undesirable.
Does glutaraldehyde work in oilfield water treatment?
Yes. It is widely used to control bacteria in injection and process water in oilfield operations, helping to prevent souring and microbially influenced corrosion.
How should glutaraldehyde be stored?
In closed, labelled containers, protected from heat and contamination, at the acidic pH at which it is supplied. Avoid storing activated solutions for extended periods and follow the storage conditions stated on the COA.
What documentation is provided?
Each lot is supplied with a Certificate of Analysis covering assay and pH, and a safety data sheet. Further documentation can be provided on request.
14. References and Further Reading
- PubChem Compound Summary, Glutaraldehyde, CID 3485 (National Library of Medicine).
- Standard industrial and pharmacopoeial references on dialdehyde chemistry and aqueous glutaraldehyde solution equilibria.
- Manufacturer technical literature on glutaraldehyde biocides and on aldehyde-based leather tanning.
Disclaimer: This article is provided for technical and informational reference only. It does not constitute medical, prescribing, legal or regulatory advice, and it does not describe clinical or pharmaceutical uses of glutaraldehyde or of any product containing it. Glutaraldehyde is an industrial chemical and must be handled and used by suitably trained personnel in accordance with applicable law and the material’s safety data sheet.
PolyBlueChem supplies Glutaraldehyde (CAS 111-30-8) as a 25% or 50% aqueous solution with a full Certificate of Analysis. For specifications, a quotation or documentation, contact our team.