ORGANIC CHEMISTRY

Organic Chemistry: The Chemistry of Carbon

Natural Sources of Organic Compounds

  • Natural Gas: Mainly methane

  • Oil: Mixture of hydrocarbons, purified by fractional distillation

  • Coal

Distillation of Crude Oil

  • C1 to C4 gases fractionating

  • C5 to Cg naphtha chemicals

  • C10 to C16 kerosine (paraffin oil)

  • C14 to C20 diesel oils

  • C20 to C50 lubricating oil

  • C20 to C70 0000 ships, fuel oil factories and fractions

  • C70 residue bitumen for roads and roofing

Types of Organic Compounds

  • All organic compounds have a carbon chain backbone (4 bonds per carbon)

  • Other elements attach to this backbone in special functional groups

  • Each homologous series reacts in a specific way

The Functional Groups

  • Only C and H, single bonds: alkanes

  • Only C and H, double bond: alkenes

  • -OH: alcohol

  • -COOH: carboxylic acid

Naming the Organic Compounds

  • Count the number of Carbons in a straight chain:

    • One: meth-

    • Two: eth-

    • Three: prop-

    • Four: but-

    • Five: pent-

    • Six: hex-

    • Seven: hept-

    • Eight: oct-

  • Look at the functional group:

    • -ane

    • -ene

    • -ol

    • -oic acid

Examples

  • Butane

  • Propanol

  • Hexene

  • Ethanoic Acid (vinegar)

Structural Isomerism

  • Compounds with the same chemical formula but different structures

  • Different functional groups or functional groups in different places

  • Is the -OH on the first or second carbon?

  • Is the C chain straight or branched?

Naming Structural Isomers

  • Number(s) at the front of the name indicate which C atom the branched carbon hangs off

  • The second word describes the branched carbon

  • If there is more than one number at the beginning of the name, methyl becomes dimethyl, trimethyl, etc.

  • The last part of the name is the longest unbroken chain

Naming with Functional Groups

  • Same rules for numbering carbons apply

  • Examples:

    • CH3CH2CH2CH2OH: Butanol (strictly butan-1-ol), Butan-2-ol, 2-methyl-propanol, 2-methyl-propan-2-ol

The Hydrocarbons: Alkanes

  • Simplest homologous series

  • General formula: CnH2n+2

  • All bonds are single bonds, making them saturated compounds

  • Largely unreactive

  • Important reactions: combustion, substitution with chlorine, and cracking

Combustion

  • Burn with a clean flame

  • Only products are carbon dioxide and water

Substitution of Chlorine

  • Catalyzed by UV light

  • Involves free radicals

  • One H at a time is replaced by chlorine, forming hydrogen chloride

Cracking of Alkanes

  • Breaking down long chain alkanes to a mixture of short-chain alkanes and alkenes

  • High temperature and pressure or a catalyst at lower temperatures and pressures

  • Shorter chains are more useful

Hydrocarbons: Alkenes

  • Have at least one double bond

  • Unsaturated compounds

  • More reactive than alkanes

  • Typical reactions: combustion, addition reactions with bromine, steam, and hydrogen

Combustion of Alkenes

  • Burn completely in air to form carbon dioxide and water

  • Burn with a smoky flame, leaving carbon particles (soot) behind

Addition Reactions

  • Small compounds can add over the double bond

  • Addition takes place symmetrically

  • Resulting compound is saturated, with only single bonds

Tests for Alkenes/Alkanes

  • Add bromine water

  • Alkene: decolourises

  • Alkane: does not decolourise

The Alcohols

  • Have the functional group -OH

  • Most common alcohol is ethanol

  • Produced through addition of steam to ethene or fermentation and distillation

Fermentation

  • Reaction of sugars with oxygen in the presence of enzymes to form alcohol and carbon dioxide

  • Mixture of ethanol and water formed can be enriched by distillation

  • Temperature must be around 35° to 37°C due to biological enzymes

Uses of Ethanol

  • Fuel: burns with a clean flame, extends non-renewable fuels

  • Solvent: dissolves organic and polar substances, used for cleaning paint, etc.

  • Alcohol for drinking

The Carboxylic Acids

  • Have the functional group -COOH

Formation of Ethanoic Acid

  • Primary alcohols are oxidized to carboxylic acids using potassium dichromate(VI) solution in the presence of dilute sulfuric acid

  • Atmospheric oxygen can also oxidize alcohol during fermentation, producing vinegar

Properties of Carboxylic Acids

  • Weak acids

  • React with bases to form salts

  • Turn damp blue litmus red

  • Starting point for manufacture of ethers, amides, polymers

Polymers

  • Long chain organic molecules formed by repeat units of simpler molecules

  • Building blocks are called monomers

  • Chains can be formed by addition or condensation

Creating Polymers

  • Process of turning monomers into polymers is called polymerization

  • Conditions used: heat, pressure, and a catalyst

Page 43:

  • Ethene is an alkene with the chemical formula C2H4.

  • It is an unsaturated hydrocarbon because it has a double bond.

  • Ethene can be produced by the cracking of crude oil products.

Page 44:

  • Ethene molecules can join together to form longer chain molecules called polymers.

Page 46:

  • Polymerization is the process of joining single monomers together to form longer chain polymers.

  • It requires pressure and a catalyst.

Page 47:

  • Ethene can undergo addition polymerization to form poly(ethene).

  • Poly(ethene) is an alkane and a saturated hydrocarbon.

  • Depending on the reaction conditions and catalyst used, ethene can make either HDPE or LDPE.

  • HDPE has higher crystallinity, a higher melting point, and is stronger and stiffer than LDPE.

Page 48:

  • Addition polymerization results in a polymer with the same basic formula as the monomer.

  • Polyethene is a type of plastic.

Page 49:

  • Poly(ethene) is made up of many ethene molecules.

Page 50:

  • Addition polymers are formed from monomers without the production of any other substance.

  • Examples of addition polymers include poly(ethene), poly(propene), PTFE, PVC, and polystyrene.

Page 51:

  • Condensation polymers form when two monomers react to release a small molecule, such as water.

  • Examples of condensation polymers are polyesters and polyamides.

Page 52:

  • Polyesters are made from a (di)carboxylic acid and a (di)alcohol.

  • Water is lost during the formation of polyesters.

Page 53:

  • Terylene is a polyester used to make crease-resistant fabric.

Page 54:

  • Polyamides are made from (di)amine and (di)carboxylic acid.

  • Water is lost during the formation of polyamides.

Page 55:

  • Nylon is a polyamide.

  • Different types of nylons can be formed depending on the initial monomers used.

Page 57:

  • Polymers have various uses such as fabrics, polythene bags, PVC pipes, polystyrene packaging, Teflon coatings, Bakelite insulation, synthetic rubber, lubricants, adhesives, and paints.

Page 58:

  • Most polymers are non-biodegradable and do not break down quickly.

  • This contributes to land-fill overfilling and unsightly litter.

  • Burning polymers can release toxic gases and harm animals.

Page 59:

  • Many natural biological molecules, such as proteins, fats, and carbohydrates, are macromolecules.