Overview
This lecture covers the basics of organic chemistry, focusing on hydrocarbons, fractional distillation, alkanes, alkenes, alcohols, acids, and polymers.
Organic Compounds & Crude Oil
- Organic compounds have carbon as the backbone of their molecules.
- Crude oil forms from ancient plankton and contains mainly hydrocarbons (molecules of only carbon and hydrogen).
- Most hydrocarbons in crude oil are alkanes, which are chains of single covalently bonded carbons with hydrogens.
Alkanes & Fractional Distillation
- The general formula for alkanes: CₙH₂ₙ₊₂.
- Alkane names end with "-ane"; prefixes indicate chain length (meth-1, eth-2, prop-3, but-4, etc.).
- Fractional distillation separates crude oil into fractions based on boiling points.
- Shorter alkanes have lower boiling points, are more flammable, and less viscous; longer alkanes are thicker and have higher boiling points.
- Key fractions: LPG (≤4 carbons), petrol, kerosene, diesel, heavy fuel oil, bitumen.
Combustion & Properties
- Complete combustion of alkanes with oxygen produces CO₂ and H₂O.
- Shorter fractions are more useful as fuels due to high flammability.
Alkenes & Testing
- Alkenes have at least one carbon-carbon double bond (C=C) and are unsaturated hydrocarbons.
- Test for alkenes: Add bromine water (orange); turns colorless if an alkene is present.
- Alkenes react with halogens and water, forming saturated compounds like alcohols.
Cracking
- Cracking breaks longer alkanes into shorter alkanes and alkenes to meet demand.
- Catalytic cracking uses zeolite at ~550°C; steam cracking uses >800°C without a catalyst.
- Cracking example: Butane → ethane + ethene.
Alcohols, Acids, and Esters
- Alcohols contain an -OH functional group and end with "-ol" (e.g., ethanol).
- Complete combustion of alcohols: CO₂ and H₂O; incomplete: CO or C and H₂O.
- Alcohol + sodium → sodium alkoxide + H₂.
- Oxidizing alcohols forms carboxylic acids (-COOH group; e.g., ethanoic acid).
- Ester formation: Alcohol + carboxylic acid → ester + H₂O.
Polymers
- Addition polymerization: Monomers (alkenes) with double bonds join to form long chains (e.g., polyethene).
- Condensation polymerization: Monomers with two different functional groups (e.g., alcohol and acid) join, releasing water (e.g., polyesters).
- Amino acids (NH₂ and COOH groups) polymerize to form proteins (polypeptides).
- DNA is a double helix made from nucleotide polymers; starch and cellulose are glucose-based natural polymers.
Key Terms & Definitions
- Hydrocarbon — Molecule containing only carbon and hydrogen.
- Alkane — Saturated hydrocarbon with single bonds (CₙH₂ₙ₊₂).
- Alkene — Unsaturated hydrocarbon with at least one C=C double bond.
- Fractional distillation — Separation technique based on boiling points.
- Cracking — Breaking long alkanes into shorter alkanes and alkenes.
- Polymer — Large molecule from repeating monomer units.
- Addition polymerization — Joining of alkene monomers without by-products.
- Condensation polymerization — Joining monomers with elimination of small molecules (e.g., water).
Action Items / Next Steps
- Review and memorize alkane and alkene formulas and names.
- Practice drawing polymer repeating units.
- Prepare for questions on testing for alkenes and properties of different oil fractions.