Org Chem (LAB)

• functional groups undergo rearrangement reactions through shifts in electron density and bonding patterns.
• Elements commonly found in organic compounds:

  • Carbon
  • Hydrogen
  • Nitrogen
  • Halogens
  • Sulfur
  • Oxygen
• Systemic approach can identify elements in organic compounds using qualitative chemical reagents
• Qualitative chemical tests rely on organoleptic approach through observation of test results
• Reaction with Cupric Oxide:

  • Detected by strongly heating the substance with CuO
  • Carbon and hydrogen oxidize to CO2 and water, respectively
  • CO2 detected by lime water, H2O detected by anhydrous cupric sulfate
  • CO2 reacts with Ca(OH)2 forming CaCO3 and H2O, resulting in a turbid solution
  • H2O reacts with anhydrous CuSO4 forming CuSO4 • 5H2O, turning white powder to blue
• Elements like nitrogen, halogens, and sulfur are difficult to detect in organic compounds as they do not ionize in solution and are bonded covalently

  • Must be converted into inorganic ions before qualitative analysis
  • Done by fusing the organic compound with sodium metal to obtain sodium extract or Lassaigne’s extract
• Reactions upon fusion with sodium metal:

  • C + N + Na → NaCN (sodium cyanide)
  • X(Cl, Br, I) + Na → NaX (sodium halide)
  • S + 2Na → Na2S (sodium sulfide)
• Soda Lime Test for Amide Nitrogen:

  • Heating amino nitrogen compounds with soda lime liberates ammonia gas
  • Presence of ammonia confirmed by red litmus turning blue
• Beilstein Test:

  • Organic halogen compounds yield a green-colored flame when burned
  • Copper oxide from the copper wire reacts with the halogen to form cupric halide, giving the flame its color
  • Fluorine does not yield a positive result
• Silver Nitrate Test:

  • Halogen reacts with silver nitrate in the presence of dilute nitric acid to form insoluble silver halide, confirming halogen presence
• Lead Acetate Test:

  • Presence of sulfur identified by the production of a brownish-black precipitate through lead acetate test
  • Organic compounds containing sulfur yield lead sulfide upon reaction with lead acetate
• Ferrox Test:

  • Oxygen detected using ferrox paper or iron (III) hexathiocyanatoferrate
  • Iron (III) ammonium sulfate reacts with potassium thiocyanate to form iron (III) hexathiocyanatoferrate, giving a red to reddish-purple color in the presence of oxygen
• Positive Test Results:

  • Carbon & Hydrogen: Lime water turns turbid, anhydrous cupric sulfate turns white powder blue
  • Nitrogen: Soda lime test yields pungent odor, red litmus turns blue
  • Halogens: Beilstein test shows green-colored flame, silver nitrate test forms white precipitate
  • Sulfur: Lead acetate test forms black precipitate
  • Oxygen: Ferrox test turns solution red to reddish-purple