Acetone: Formula, Boiling Point, Density and Industrial Grades

The short answer

Acetone is the simplest ketone. Formula C₃H₆O, structure CH₃COCH₃, CAS 67-64-1, molecular weight 58.08 g/mol, boiling point 56 °C, density 0.79 g/cm³.

Three properties explain almost every use it has. It dissolves a very wide range of organic materials. It is completely miscible with water. And it evaporates quickly and cleanly, leaving no residue. The cost of that last property is a flash point of about −20 °C, which means every drum, line and tank has to be treated as a flammable liquid installation.

Formula, structure and identifiers

The molecule is a carbonyl group, C=O, with a methyl group on each side. That carbonyl is the reactive centre and the reason acetone behaves so differently from an alcohol of similar size.

Physical properties

Note the vapour density of 2. Acetone vapour is twice as heavy as air, so it collects in pits, sumps and the bottom of a tank rather than dispersing upwards. That single number governs how a store room is ventilated.

Why acetone boils at 56 degrees C

Compare acetone with isopropyl alcohol. Both are three-carbon oxygenates of almost the same molecular weight, yet acetone boils at 56 °C and isopropanol at 82 °C. The difference is hydrogen bonding.

Isopropanol has an O–H group, so its molecules hydrogen bond to each other and hold the liquid together. Acetone has an oxygen that can accept a hydrogen bond but no hydrogen on oxygen to donate one, so acetone molecules cannot hydrogen bond to each other. They are held together only by dipole–dipole attraction, which is weaker, and the liquid gives up its molecules more easily.

The same asymmetry explains the next section.

Why it mixes with both water and solvents

Acetone is miscible with water in every proportion and also dissolves oils, waxes, resins and most polymers short of the highly crystalline ones. Very few solvents do both.

The carbonyl oxygen accepts hydrogen bonds from water, which handles the water side. The two methyl groups give the molecule a non-polar surface, which handles the organic side. The result is a solvent that bridges aqueous and organic systems, which is why it turns up as a coupling solvent, a cleaning solvent for water-wet parts, and a drying aid — rinse a wet component in acetone and the acetone carries the water away and then evaporates.

The practical limit is plastics. Acetone attacks polystyrene, ABS, polycarbonate and many acrylics, and swells or dissolves PVC. Test compatibility before using it near a plastic component.

How acetone is made

The overwhelming majority of the world's acetone is a co-product of phenol. In the cumene process, benzene and propylene are combined to make cumene, which is oxidised to cumene hydroperoxide and then cleaved with acid into phenol and acetone. Roughly 0.6 tonnes of acetone appear for every tonne of phenol.

That coupling has a commercial consequence worth knowing: the acetone price is driven as much by phenol demand as by acetone demand, because supply is set by someone else's production plan. A secondary route, catalytic dehydrogenation of isopropyl alcohol, is used where on-purpose acetone is wanted and tends to set a ceiling on the price.

Technical, AR, HPLC and pharmacopoeial grades

The distinction that trips people up is AR versus HPLC. AR grade is clean by mass but is not tested for the thing that matters in chromatography — UV-absorbing impurities at parts-per-million level. Use AR in a chromatograph and you get baseline drift and ghost peaks even though the certificate says 99.5 %.

Scapex Exports supplies acetone technical grade, acetone AR grade and acetone HPLC grade.

What acetone is used for

• Solvent and cleaning. Degreasing metal, cleaning printing and coating equipment, stripping uncured resin, removing adhesive residue.
• Coatings and inks. A fast-evaporating component in lacquers, nitrocellulose systems and printing inks. In several jurisdictions acetone is exempt from VOC counting, which keeps it in formulations that would otherwise have moved on.
• Chemical intermediate. Feedstock for methyl methacrylate, bisphenol A, mesityl oxide, methyl isobutyl ketone and diacetone alcohol.
• Pharmaceutical processing. Crystallisation, granulation and washing solvent, recovered and controlled as a Class 3 residual solvent.
• Acetylene storage. Acetylene cylinders are packed with a porous mass saturated in acetone, which dissolves about 25 times its own volume of acetylene per atmosphere and lets the gas be stored safely.
• Cellulose acetate and fibre. Spinning solvent in acetate fibre and film production.
• Laboratory. Glassware rinsing and rapid drying.

Flammability, handling and export documents

Acetone is a Class 3 flammable liquid, UN 1090, packing group II. A flash point near −20 °C means the vapour above the liquid is ignitable at any ordinary ambient temperature, and the wide 2.6 to 12.8 % explosive range means a leak reaches an ignitable mixture quickly.

• Ignition control. Bond and earth drums and receiving vessels before transfer. Acetone flowing through a pipe generates static, and the vapour needs very little energy to ignite.
• Ventilation. Vapour is heavier than air. Extract at low level; do not rely on roof vents.
• Storage. Cool, shaded, well ventilated flammable store, away from oxidisers. Acetone reacts violently with strong oxidising agents, and with chloroform in the presence of a base.
• Health. Defatting to skin, eye irritation, and central nervous system depression at high vapour concentrations. Use nitrile or butyl gloves for short contact, splash goggles, and monitor the workplace exposure limit in force locally.
• Materials. Carbon steel and stainless steel are fine. Avoid natural rubber, EPDM, polystyrene, ABS, polycarbonate and many acrylics.
• Packing. 160 kg and 200 litre MS or epoxy-lined drums, IBCs, ISO tanks and bulk.

Acetone is a listed precursor chemical in several international control regimes, so some destinations require an import authorisation, an end-use declaration or pre-export notification. A compliant supplier will ask about end use and consignee before quoting; that is normal diligence, not obstruction.

An export consignment should carry a certificate of analysis stating assay, water, acidity, non-volatile residue and colour; a 16-section GHS safety data sheet; a dangerous goods declaration with UN 1090, Class 3, PG II; commercial invoice and packing list; certificate of origin; and any end-use or import permit the destination requires.

Enquire with a specification

Acetone is supplied by Scapex Exports as a manufacturer and supplier from qualified Indian producers, in technical, analytical reagent, HPLC and pharmacopoeial grades, with certificate of analysis, safety data sheet and full export and dangerous goods documentation.

Send the grade, assay, water limit, packing, quantity and destination port, together with the end use, and you will get a quotation written against that specification rather than a generic one.

Frequently asked questions