Calorimetric determination of the heat of precipitation of pseudoephedrine racemic compound—its agreement with the heat of solution

✍ Scribed by Madhu Pudipeddi; Theodore D. Sokoloski; Sarma P. Duddu; Jens T. Carstensen

• Publisher: John Wiley and Sons
• Year: 1995
• Tongue: English
• Weight: 494 KB
• Volume: 84
• Category: Article
• ISSN: 0022-3549
• DOI: 10.1002/jps.2600841017

✦ Synopsis

The heat of precipitation of dl-pseudoephedrine was determined by direct calorimetry using a Tronac isoperibolic calorimeter. The precipitation of dl-pseudoephedrine was induced by mixing aqueous solutions of the two enantiomers, namely, d- and l-pseudoephedrine, directly in the calorimeter. The molar heat of precipitation of dl-pseudoephedrine was -2.7 and -3.0 kcal/mol at 25 and 30 degrees C, respectively. The aqueous solubility of dl-pseudoephedrine was determined over a temperature range of 20-40 degrees C. The van't Hoff solubility plot was nonlinear. The apparent heat of solution at saturation was obtained from the solubility data using a nonlinear regression model. A good agreement between the magnitude of the apparent heat of solution at saturation and the heat of precipitation was noticed at both 25 and 30 degrees C.