Organic Chemistry Notes

Fossil Fuels

  • Three types:
    • Petroleum (crude oil)
    • Coal
    • Natural gas

Petroleum

  • A mixture of hydrogen and carbon (hydrocarbons).
  • Purified using fractional distillation.

Fractional Distillation

  1. Heat petroleum until it vaporizes.
  2. Vapor rises through a column.
  3. Substances condense at their respective boiling points.
  4. Collected based on boiling point.
  • The gas that travels farthest is the lightest (smallest number of carbon atoms).
  • The heaviest sinks to the bottom (greatest number of carbon atoms).

Acronym to remember the sequence of fractions: Please Promise Not Kick Doctor Limbs Butt

  • P: Petroleum gas
  • P: Petrol
  • N: Naphtha
  • K: Kerosene
  • D: Diesel oil
  • L: Lubricating oil
  • B: Bitumen

Uses

  • Smaller particles: daily life (cooking, car fuel).
  • Heavier molecules: factories (feedstock, rubber, medicine, airplanes, lorries, machines, roads).

Trend Going Down the Column

  • Size increases.
  • Intermolecular forces get stronger (higher melting and boiling points).
  • Less flammable.
  • Viscosity increases (stickier, waxier).
  • Lower volatility.
  • Demand is highest for the first two (petroleum gas and petrol) due to daily use.

Cracking

  • Breaking large hydrocarbons into smaller, more useful hydrocarbons.
  • Example: prawn cracker or butt crack analogy.

Fossil Fuel Components

  • Coal
  • Petroleum
  • Natural gas (mainly methane)

Applications of Petroleum

  • Fuels for cooking.
  • Fuels for cars.

Environmental Impact of Petroleum

  • Drilling on the seabed causes air and water pollution.
  • Petroleum is finite and non-renewable; conservation is essential.

Homologous Series

  • Family of organic compounds.
  • Same general formula.
  • Similar chemical properties (same reactions).
  • Physical properties gradually change.

Example: WuTu Family (Analogy)

  • Same surname (general formula).
  • Similar looks (chemical reactions).
  • Different sizes (physical properties).

Examples of Homologous Series

  • Alkane, alkene, alcohol, and carboxylic acid.
Alkane
  • Single C-C and C-H bonds.
  • General formula: C<em>nH</em>2n+2C<em>nH</em>{2n+2}
Alkene
  • At least one C=C double bond.
  • Minimum of two carbon atoms to form a double bond.
  • General formula: C<em>nH</em>2nC<em>nH</em>{2n}
Alcohol
  • -OH (hydroxyl) group.
Carboxylic acid
  • -COOH (carboxyl) group.

Trends Within Alkane Family

  • Adding CH<em>2\text{CH}<em>2 to get the next member (CH</em>4\text{CH}</em>4, C<em>2H</em>6\text{C}<em>2\text{H}</em>6, C<em>3H</em>8\text{C}<em>3\text{H}</em>8).

Molecular vs. Structural Formula

Molecular Formula

  • Summarizes elements (e.g., C<em>2H</em>6\text{C}<em>2\text{H}</em>6).
  • Does not show how atoms are bonded.

Structural Formula

  • Shows how atoms are bonded to one another.

Cracking (Detailed)

  • Breaking down large alkane molecules into smaller, useful molecules.
  • Performed at high pressure and temperature.

Possible Pathways

  1. Alkane → Alkene + Alkane:
    • Example: C<em>10H</em>22→C<em>8H</em>18+C<em>2H</em>4\text{C}<em>{10}\text{H}</em>{22} \rightarrow \text{C}<em>8\text{H}</em>{18} + \text{C}<em>2\text{H}</em>4
  2. Alkane → Alkene + Hydrogen:
    • Cracking is random; cannot control the pathway.

Lab Cracking

  • Place large alkane molecules over high heat to break carbon chains.
  • Collect smaller alkenes.

Balancing Chemical Equations

  • Balance atoms: same number of each type of atom on both sides.
  • Combustion: Balance carbon first, then hydrogen, then oxygen.

Complete Combustion of Hexane

  • C<em>6H</em>14+192O<em>2→6CO</em>2+7H2O\text{C}<em>6\text{H}</em>{14} + \frac{19}{2} \text{O}<em>2 \rightarrow 6 \text{CO}</em>2 + 7 \text{H}_2\text{O}
  • Remove fraction: 2C<em>6H</em>14+19O<em>2→12CO</em>2+14H2O2\text{C}<em>6\text{H}</em>{14} + 19 \text{O}<em>2 \rightarrow 12 \text{CO}</em>2 + 14 \text{H}_2\text{O}

Incomplete Combustion

  • Limited oxygen.
  • Products: soot and carbon monoxide (CO).
  • Carbon monoxide is poisonous: binds to red blood cells, causes breathing difficulty and death.

Catalysts in Cracking

  • Powdered catalysts increase the surface area for reaction (collision theory).
  • Greater surface area → more collisions → faster rate.

Cracking and Oil Refinery Demands

  • Cracking converts long carbon chains into smaller hydrocarbons (like petrol) to meet demand.

Naming Organic Molecules

  • Three parts: prefix (branch), stem (longest carbon chain), suffix (family).

Example: 2-methylbutanol;

*   *ol*: alcohol family.
*   *but*: four-carbon stem.
*   *methyl*: one-carbon branch on the second carbon.

Number of Carbons

  • 1: Meth
  • 2: Eth
  • 3: Prop
  • 4: But
  • 5: Pent
  • 6: Hex
  • 7: Hept
  • 8: Oct
  • 9: Non
  • 10: Dec

Family Suffixes

  • -ane: Alkane
  • -ene: Alkene
  • -ol: Alcohol
  • -oic acid: Carboxylic acid

Naming Example 1

  • Single C-C and C-H bonds: Alkane.
  • Four carbons in the stem: Butane.

Naming Example 2

  • Single bonds: Alkane.
  • Three carbons in the stem: Propane.
  • One-carbon branch (methyl) on the second carbon: 2-methylpropane.

Functional Groups

  • Reactive part of the molecule (atom or group of atoms).

Examples

  • Alkene: Double bond.
  • Alcohol: -OH group.
  • Carboxylic acid: -COOH group.
  • Ester: COO group.

Saturated vs. Unsaturated

  • Saturated: Single bonds only (alkanes).
  • Unsaturated: Contains double or triple bonds (alkenes, alkynes).