49. PARALDEHYDE

Introduction

Paraldehyde is an important pharmaceutical compound used mainly for its sedative, hypnotic, and anticonvulsant actions. It has been used for many years in the management of seizures, excitement, and insomnia. These notes explain its chemistry and properties in simple, easy-to-understand language.

Chemical Information

  • Formula: C6H12O3
  • IUPAC Name: 2,4,6-Trimethyl-1,3,5-trioxane

Preparation

Paraldehyde is prepared by treating acetaldehyde with an acid catalyst, usually concentrated sulphuric acid. This reaction converts acetaldehyde into a cyclic trimer known as paraldehyde.

Tests for Purity

Several quality control tests are performed to ensure that paraldehyde is pure and safe for use.

  • Congealing Range: 10–13°C
  • Distillation Range: 123–126°C
  • Refractive Index: 1.403–1.406 (1% solution at 20°C)
  • Density: 0.991–0.996 g/ml
  • Acetaldehyde Content: Should not exceed the amount equivalent to 0.8 ml of 0.5 M NaOH
  • Acidity: Checked using hydroxylamine hydrochloride. Excess acid after oxime formation should require less than 1.5 ml of 0.1 M NaOH.
  • Chlorides & Sulphates: Should pass the official limit tests and contain no detectable traces.
  • Non-volatile Matter: Less than 0.06% w/v
  • Peroxides: Identified by titration with sodium thiosulfate. Should consume less than 2 ml of 0.1 M sodium thiosulfate.

Uses of Paraldehyde

Paraldehyde has several clinical applications:

  • Used to treat convulsive disorders, especially when rapid sedation is needed.
  • Used earlier in the management of alcohol withdrawal symptoms.
  • Provides sedation and relaxation in patients with nervousness or mental agitation.
  • Acts as a hypnotic to induce sleep.
  • Used in obstetric analgesia to reduce pain.

Student Notes

Paraldehyde is an old but important drug in pharmaceutical chemistry. Its unique trioxane ring structure, purity tests, and clinical actions make it a common exam topic. Always remember its preparation from acetaldehyde and its role as a sedative-hypnotic agent.

Detailed Notes:

For PDF style full-color notes, open the complete study material below:

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

Share your love