43. CHLORBUTOL

Chlorbutol (Chloretone)

Formula: C₄H₇Cl₃O

IUPAC Name: 1,1,1-Trichloro-2-methyl-2-propanol

Other Names: Chlorobutanol, Chloretone

Preparation

Chlorbutol is prepared by directly combining acetone with chloroform in the presence of solid potassium hydroxide (KOH). This reaction produces the final trichloro alcohol compound.

Test for Purity

• Appearance: Freely soluble and polar. A 50% w/v solution in ethanol should appear clear.
• Acidity: The sample should not consume more than 0.1 ml of 0.1 M NaOH.
• Chlorides: Limit test using silver nitrate. Allowed limit: less than 500 ppm.
• Water: After drying, moisture content should be below 6%.
• Sulphated Ash: Should be less than 0.1%.

Assay

The assay is performed by hydrolysing a weighed quantity of chlorbutol in alcohol by refluxing with aqueous sodium hydroxide (NaOH).

Steps involved:

• Hydrolysis releases chloride ions.
• These chloride ions are estimated using Volhard’s method with N/10 silver nitrate (AgNO₃) and N/10 ammonium thiocyanate (NH₄SCN).
• A small amount of nitrobenzene is added before titration to help coagulate the AgCl precipitate.

The final result is expressed as the hemihydrate form. Here, 1000 ml of N/10 AgNO₃ corresponds to 1/30 of C₄H₇Cl₃O · ½H₂O.

Uses

• Chlorbutol has mild antibacterial and antifungal activity.
• Used as a preservative (usually 0.5%) in:
  • injections
  • eye drops
  • mouthwashes
  • ointments and creams
  • cosmetic preparations

Detailed Notes:

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PATH: PHARMD/PHARMD NOTES/ PHARMD FIRST YEAR NOTES/ ORGANIC CHEMISTRY/ PHARMACEUTICAL ORGANIC CHEMISTRY/ CHLORBUTOL.