Organic Chemical Reactions

Organic Chemical Reactions

1. Substitution (pg. 1025)

• Definition: The replacement of one atom (or group) by another atom (or group).
• Note: Substitution is the only way to add a halogen to an alkane.
• Example:
  • propane + $Br_2$ → 2-bromopropane or 1-bromopropane (also could be 1,2- or 1,3- or 1,1- or 2,2-dibromopropane)
• Reaction Equation and Conditions:
  $C-C-C(H)(H)(H)(H)(H)(H)(H)(H) + Br-Br \rightarrow C-C-C(H)Br(H)Br(H)(H)(H)(H) + Br(H)$
• Conditions: Catalyst, heat, (pressure)

2. Halogenation (pg. 1023)

• Definition: The addition of a halogen (group VII element) to a multiple bond (the halogen atoms add across a pi bond).
• Example:
  • propene + $Cl_2$ → 1,2-dichloropropane
• Reaction Equation and Conditions:
  $CH<em>3CH=CH</em>2 + Cl<em>2 \rightarrow CH</em>3CHClCH_2Cl$
• Conditions: Room temperature

3. Hydrogenation (pg. 1023)

• Definition: The addition of $H_2$ to a multiple bond (across a pi bond).
• Also known as: saturation
• Commercial Use: Used commercially in the production of margarine.
• Example:
  • 1-butene + $H_2$ → butane
• Reaction Equation and Conditions:
  $CH<em>3CH=CHCH</em>2 + H<em>2 \rightarrow CH</em>3CH<em>2CH</em>2CH_3$
• Conditions: Catalyst, heat, pressure

4. Hydrolysis (pg. 1023)

• Definition: The addition of a water molecule to a double bond.
• Example:
  • propene + $H_2O$ → propan-2-ol or propan-1-ol
• Reaction Equation and Conditions:
  $CH<em>3CH=CH</em>2 + H<em>2O \rightarrow CH</em>3CH(OH)CH_2$
• Conditions: Catalyst, acid catalyst

5. Elimination (pg.1027)

• Definition: The loss of a small molecule from a larger molecule.
• Special Cases: When the small molecule is $H_2O$, the process is also referred to as “condensation” or “dehydration”.
• Example:
  • ethanol → ethene + water
• Reaction Equation and Conditions:
  $C-C(H)(H)(OH)(H)(H) \rightarrow C=C(H)(H)(H) + H_2O$
• Conditions: Heat

6. Esterification (pg. 1030)

• Definition: The condensation reaction that joins an alcohol with a carboxylic acid to produce an ester.
• Example:
  • Producing isopentyl acetate: 3-methylbutan-1-ol + ethanoic acid → 3-methylbutyl ethanoate + water
  • (isopentyl alcohol) + (acetic acid) → (isopentyl acetate)
• Reaction Equation and Conditions:
  $CH<em>3CHCH</em>2CH<em>2OH + CH</em>3COOH \rightarrow CH<em>3CHCH</em>2CH<em>2O(CO)CH</em>3 + H_2O$
• Conditions: $H^+$, heat

7. Polymerization

• Definition: The conversion of “monomers” into “polymers”. I.e., the joining of small molecules to form large molecules with repeating units.
  • a) Addition (pg. 1023):
    • Example: eth(yl)ene → polyeth(yl)ene
    • Reaction Equation:
      $n(CH<em>2=CH</em>2) \rightarrow …-CH<em>2-CH</em>2-CH<em>2-CH</em>2-CH<em>2-CH</em>2-…$
  • b) Condensation (pg. 1031):
    • **General Reaction (for Dacron: replace $R<em>1$ with -$CH</em>2-CH<em>2$- and $R</em>2$ with benzene):
      • diol + dicarboxylic acid → polyester + $H_2O$
      • (ethylene glycol) + (terephthalic acid) → (Dacron)
    • Reaction Equation:
      $H-O-(CO)-R<em>1-H + H-(CO)-O-R</em>2-(CO)-OH \rightarrow …-R<em>1-(CO)-O-R</em>2-(CO)-O-… + H_2O$
• Conditions: Room temperature, catalytic process

8. Oxidation (pg. 1028)

• Definition: (More) oxygen atoms are placed on an organic molecule.
• Example:
  • ethanal + $K<em>2Cr</em>2O_7$ → ethanoic acid
• Reaction Equation and Conditions:
  $H-C-C(H)(H)O + K<em>2Cr</em>2O_7 \rightarrow H-C-C(O)(O)H$
• Conditions: $H<em>2SO</em>4$, $Cr<em>2(SO</em>4)<em>3$, $K</em>2SO<em>4$, $H</em>2O$

Questions to Consider:

1. Define addition reaction. Which of these reactions are addition reactions? Which reaction is the opposite of an addition reaction?
2. Define condensation reaction. Which of these reactions are condensation reactions?
3. Based on these reactions, how could you make the following chemicals (draw reaction, showing reactants, products, and conditions. Also indicate the type of reaction):
   • 1,2-dichlorocyclopentane
   • octane (using oct-4-yne)
   • 2,2,3,3-tetrabromopentane
   • but-1-ene
   • propanoic acid
   • ethanol
   • ethyl propanoate