Reagents for organic chemistry

• Complete combustion

  • Sufficient/excess oxygen
  • Produces carbon dioxide and water
• Incomplete combustion

  • insufficient oxygen
  • Produces carbon monoxide, soot and water
• Substitution (Alkane)

  Reagent: Halogen

  Condition: UV light

  • forms another molecule

  
• Cracking (larger hydrocarbon molecules)

  Conditions: High temperature (500-700), Pressure of about 1 atm and finely divided catalysts, Al2O3 or SiO2
• Test for saturation: Red-brown aqueous bromine

  Unsaturated hydrocarbons: Red brown aqueous bromine turns colourless or decolourises

  Saturated hydrocarbons: Red-brown aqueous remains red-brown
• Addition reaction of alkenes

  • carbon carbon double bond breaks to form new single bond and hence an unsaturated combines with another substance to form a new saturated compound

  
• Hydrogenation

  Reagent: Hydrogen gas (H2)

  Condition: Nickle catalyst, 150degree celcius

  • alkene -> alkane
  • e.g vegetable oil -> magarine
• Hydration

  Reagent: Steam (H2O)

  Condition: 300degree celcius, 60 atm, phosphoric acid (H3PO4)

  • alkene -> alcohol
• Bromination

  Reagent: Aqueous bromine (Br2)

  Condition: Room temperature

  • CnH2n + Br2 -> CnH2nBr2

  
• Oxidation of alcohol

  Reagents: acidified potassium manganate (IV) (KMnO4) (aq)/ Oxygen gas in presence of bacteria

  Condition: heat/warm

  Observation: purple acidified KMnO4 turns colourless

  • alcohol -> carboxylic acid
• Obtaining ethanol


  Fermentation

  • slow breakdown of starch/glucose into ethanol

  Conditions: 37 degrees, anaerobic (absence of oxygen) and yeast as catalyst

  Synthesis of ethene

  • catalytic addition of steam to ethene
  • conditions: 300 degrees, 60atm, phosphoric acid catalyst