What Is the Molar Mass of Acetone (CH3COCH3)?

Acetone molecular formula: CH3COCH3 (or C3H6O)

Structural formula: CH3 — C(=O) — CH3

IUPAC name: Propan-2-one Common name: Acetone, dimethyl ketone

Acetone is a ketone — the carbonyl group (C=O) is flanked by two methyl groups. It has a trigonal planar geometry around the carbonyl carbon. The carbonyl group makes acetone polar, allowing it to dissolve both polar and non-polar substances, which explains its usefulness as a solvent.

Molecular formula of acetone: C3H6O

Step-by-step calculation:

• Carbon (C): 3 atoms × 12 g/mol = 36 g/mol
• Hydrogen (H): 6 atoms × 1 g/mol = 6 g/mol
• Oxygen (O): 1 atom × 16 g/mol = 16 g/mol

Total molar mass = 36 + 6 + 16 = 58 g/mol

Atomic masses used: C = 12, H = 1, O = 16 (standard values).

Alternatively counting atoms in CH3COCH3:

• C: 1 (CH3) + 1 (CO) + 1 (CH3) = 3 carbon atoms
• H: 3 (CH3) + 3 (CH3) = 6 hydrogen atoms
• O: 1 (C=O) = 1 oxygen atom Confirming C3H6O → molar mass 58 g/mol.

Physical properties of acetone:

• Appearance: Colourless liquid
• Odour: Characteristic sweet, fruity smell
• Boiling point: 56.1°C
• Melting point: −94.7°C
• Density: 0.791 g/cm³ at 20°C (lighter than water)
• Miscibility: Completely miscible with water, ethanol, diethyl ether, and most organic solvents
• Vapour pressure: 24.6 kPa at 20°C (highly volatile)
• Flash point: −20°C (highly flammable)
• Auto-ignition temperature: 465°C

Acetone is one of the most volatile common solvents. It evaporates quickly at room temperature, which is why it feels cold on the skin.

Acetone undergoes typical ketone reactions:

1. Nucleophilic addition: Reacts with HCN to form cyanohydrin: CH3COCH3 + HCN → (CH3)2C(OH)CN

2. Iodoform reaction: Gives iodoform (CHI3) — a yellow precipitate — with I2/NaOH, confirming the methyl ketone structure.

3. Aldol condensation: Two acetone molecules condense under basic conditions: 2CH3COCH3 → (CH3)2C(OH)CH2COCH3 (diacetone alcohol)

4. Reduction: Acetone is reduced to isopropanol (2-propanol) using NaBH4 or LiAlH4: CH3COCH3 + [H] → CH3CH(OH)CH3

5. Does not give silver mirror test (Tollens') or reduce Fehling's solution — distinguishes ketones from aldehydes.

Acetone is one of the most important industrial solvents and chemicals:

1. Solvent: Widely used to dissolve paints, varnishes, resins, fats, and plastics. The most common use of nail polish remover.
2. Manufacture of chemicals: Used to produce methyl methacrylate (for plexiglass), bisphenol A (for polycarbonate plastics and epoxy resins).
3. Pharmaceutical industry: Used as a solvent in drug synthesis and formulation.
4. Laboratory solvent: Used for cleaning glassware and as a reaction solvent.
5. Food industry: Used as a food-grade solvent in some applications.
6. Biological: Acetone is naturally produced in the human body during fat metabolism (ketosis) and is found in breath and urine of diabetic patients.
7. Antiseptic preparations: Found in some antiseptic skin cleansers.