video tutorial Dry distillation of calcium propionate and benzoate

Summary

• Objective: synthesize propiophenone by distilling a 1:2 mixture of calcium propionate and calcium benzoate prepared from calcium chloride with sodium benzoate and from calcium hydroxide with propionic acid.
• Procedure and initial results:
  • 110 g of dried salt mixture placed in a 500 mL round-bottom flask and heated for simple distillation.
  • Initial distillate appeared at high heat with a vapor temperature around 85°C.
  • Flask heated further with a gas flame; contents turned brown/black and a second distillate (yellow) appeared as temperature rose.
  • Distillation continued for about 3 hours, yielding roughly 35 mL of orange liquid containing a drop of water.
  • Distillate had a strong petrochemical, spicy aroma and caused mild eye irritation.
• Workup:
  • Distillate washed with 20 mL water, separated, emulsions formed, then washed again with 20 mL water.
  • Product dried with anhydrous MgSO4 and redistilled to analyze fractions.
• Fractions from redistillation:
  • Fraction 1: ~50 mL collected; distillation range 75–80°C; ~6 mL of colorless liquid with an aroma reminiscent of ethyl acetate.
  • Fraction 2: distills around 130°C; only a few mL; has a spicy petrochemical aroma; contains ethyl acetate impurity from propionic acid and possibly a straight-chain ketone as a side product.
  • Fraction 3: distills 190–200°C; ~30 mL; yellow color with a sweet, honey-like aroma; contains acetophenone and other compounds; likely includes some propiophenone but uncertain.
• Analytical observations on fraction 3:
  • Rough melting point: fraction 3 melted between 0 and 10°C; another sample of 10 mL used to determine density.
  • Iodoform test for alpha-methyl ketones showed a strong reaction when compared to acetone, with some yellow coloration beyond that of the fraction 3 sample.
  • Ferric chloride test for phenols: fraction 3 did not produce a purple color, indicating no phenolic/aromatic hydroxyl groups.
• Interpretation:
  • Fraction 1 may be variable in composition and not clearly identified from the tests.
  • Fraction 2 likely contains ethyl acetate impurity from propionic acid and may include a straight-chain ketone as a by-product.
  • Fraction 3 appears to contain acetophenone and other compounds; there is evidence suggesting the presence of propiophenone, but a significant amount of work would be required to confirm purity and quantify it.
• Conclusion: while the synthesis route is attractive, achieving a pure product would require substantial purification and likely yield only small amounts; nonetheless, the experiment was informative and enjoyable.