Isopropyl alcohol (IPA, isopropanol, CAS 67-63-0) and acetone (CAS 67-64-1) have very similar chemical formulas - both molecules contain three carbon atoms with a substitution at the middle carbon. The substituted group is different: acetone carries an oxo (C=O) group, while isopropyl alcohol carries a hydroxyl (OH) group. This single difference drives most of the practical differences between the two solvents.
1. Chemical Structure
| Isopropyl alcohol (IPA) | Acetone | |
|---|---|---|
| CAS No. | 67-63-0 | 67-64-1 |
| Formula | C₃H₈O (alcohol) | C₃H₆O (ketone) |
| Functional group | Hydroxyl (-OH) | Carbonyl (C=O) |
| Family | Secondary alcohol | Ketone |
2. Physical Properties Compared
| Property | IPA | Acetone |
|---|---|---|
| Boiling point | 82.4 °C | 56 °C |
| Flash point (closed cup) | ≈ 12 °C | ≈ -20 °C |
| Evaporation rate | Slow to moderate | Very fast |
| Polarity | Polar protic | Polar aprotic |
| Water miscibility | Fully miscible | Fully miscible |
3. Solvency Behaviour
Both compounds are highly soluble and dissolve a wide range of non-polar and polar compounds. Acetone, as a polar aprotic solvent, is a stronger solvent for many non-polar materials and is highly effective on oils, greases, resins and many plastics (with caution - it can soften or attack some plastics). Isopropyl alcohol, as a polar protic solvent, is a gentler cleaning solvent that leaves less residue and is widely compatible with electronics and coatings.
4. Typical Uses
Acetone: laboratory glassware and tube cleaning (excellent solvent for organic residues); paint thinner and coating remover; resin and adhesive dilution; general degreasing in industrial processes. See our acetone product specifications for available grades.
Isopropyl alcohol: disinfectant and antiseptic (e.g. 70% IPA solution as a rubbing alcohol for skin preparation before injection); electronics and precision-instrument cleaning; solvent for paints, coatings and cleaners; degreaser in industrial and household use. See our isopropyl alcohol product specifications for available grades.
Why 70% IPA Is More Effective Than Higher Concentrations?
A 70% IPA/water solution is widely regarded as the optimal concentration for disinfection - not 90% or 99% IPA. At concentrations above roughly 91%, IPA evaporates too quickly and denatures surface proteins on contact, forming a protective coagulated layer that actually shields microorganisms underneath rather than killing them. The water content in a 70% solution slows evaporation, allowing the alcohol to penetrate the cell wall and denature proteins throughout the microorganism, which is why 70% IPA is the standard concentration in most medical-grade antiseptic and surface-disinfectant products.
5. Safety Notes
Both are flammable: acetone has a much lower flash point (≈ -20 °C) and evaporates faster, so it presents a higher fire hazard and requires strict ventilation and grounding.
IPA has lower acute toxicity and a higher flash point, making it the safer choice for routine cleaning where its solvency is sufficient.
Do not mix the two unless the application requires it; refer to the SDS of each material before use. For detailed handling, storage and exposure-limit data, consult the SDS for isopropyl alcohol and SDS for acetone.
Selection Guide
Choose acetone when you need maximum solvency for resins, greases and uncured adhesives, and where fast evaporation is acceptable. Choose isopropyl alcohol when cleaning electronics, disinfecting surfaces, or when a gentler solvent with less residue is preferred.
Frequently Asked Questions
Which Is Safer: IPA Or Acetone?
For routine cleaning, IPA is generally safer: it has a higher flash point (≈ 12 °C vs ≈ -20 °C), lower acute toxicity and gentler solvency. Acetone requires stricter fire precautions.
Can I Use Acetone Instead Of Isopropyl Alcohol?
Not always. Acetone attacks some plastics and coatings and evaporates much faster; verify material compatibility before substitution.
Which Evaporates Faster, Acetone Or IPA?
Acetone evaporates much faster (boiling point 56 °C vs IPA 82.4 °C), which can be an advantage or a drawback depending on the application.
Why Is 70% IPA Used For Disinfection?
A 70% IPA/water solution penetrates cell walls more effectively and evaporates slowly enough to stay in contact longer, making it more effective for disinfection than 100% IPA.
Need IPA or acetone for your production? Contact our technical team for grade specifications, COA, and bulk pricing.
