Carbon and its Compounds

Importance of Carbon Compounds

• Carbon compounds are integral to daily life, found in:
  • Toothpaste
  • Soap
  • Cosmetics
  • Medicines
  • Clothes
  • Paper
  • Food (e.g., bread)
• Burning carbon compounds results in carbon (black substance).

Carbon in Nature

• Earth's crust: 0.02% carbon in carbonates, hydrogen carbonates, coal, and petroleum.
• Atmosphere: 0.3% carbon dioxide.

Differences Between Ionic Compounds and Carbon Compounds

• Conductivity:
  • Carbon compounds: Poor conductors of electricity.
  • Ionic compounds: Good conductors of electricity.
• Boiling/Melting Points:
  • Carbon compounds have lower boiling points (e.g., acetic acid: 118°C) compared to ionic compounds (e.g., sodium chloride: 1413°C).
• Molecular Attraction:
  • Carbon compounds have weaker molecular attraction.
  • Ionic compounds have strong molecular attraction.
• Bonding:
  • Carbon compounds do not form ions.
  • Ionic compounds form ions.

Bonding in Carbon Compounds

• Atomic Number: Carbon = 6 (4 electrons in the outer shell).
• Carbon's valency is 4.
• Carbon cannot gain/lose 4 electrons due to:
  • Difficulty in holding 10 electrons (if gaining).
  • High energy requirement to lose 4 electrons.
• Covalent Bonding:
  • Carbon forms covalent bonds by sharing electrons.

Covalent Bond Formation Examples

• Hydrogen:
  • 2 hydrogen atoms share 1 electron each to form H₂ (single bond).
• Oxygen:
  • 2 oxygen atoms share 4 electrons (double bond).
• Nitrogen:
  • 2 nitrogen atoms share 6 electrons (triple bond).
• Methane (CH₄):
  • 1 carbon atom forms 4 single covalent bonds with hydrogen.

Versatility of Carbon

1. Catenation:
   • Carbon's ability to bond with itself to form long chains and rings (strong stability).
   • Other elements (e.g., silicon) also show catenation but less effectively.
2. Valency:
   • Carbon can bond with 4 other atoms (hydrogen, oxygen, nitrogen, etc.).
   • Strong bonds due to small atomic size, leading to stable compounds.

Saturated and Unsaturated Carbon Compounds

• Saturated Compounds:
  • Single bonds (e.g., C₂H₆ - Ethane).
• Unsaturated Compounds:
  • Double or triple bonds (e.g., C₂H₄ - Ethene, C₂H₂ - Ethyne).
• Unsaturated compounds are more reactive than saturated ones.

Structural Isomers

• Different structures with the same molecular formula (e.g., butane can be linear or branched).
• Cyclic Compounds: Carbon compounds can form rings (e.g., cyclohexene, benzene).

Hydrocarbons

• Alkanes: Saturated hydrocarbons (single bonds).
• Alkenes: Unsaturated hydrocarbons with double bonds.
• Alkynes: Unsaturated hydrocarbons with triple bonds.

Functional Groups and Homologous Series

• Functional Groups: Atoms/groups that replace hydrogen in hydrocarbons (e.g., alcohols, acids).
• Homologous Series: Series of compounds with similar properties differing by CH₂ units (e.g., alkanes, alkenes).

Nomenclature of Carbon Compounds

1. Count carbon atoms in the main chain.
2. Identify bond types (single, double, triple).
3. Identify functional groups.

• Prefixes:

  • 1 carbon: Meth-
  • 2 carbons: Eth-
  • 3 carbons: Prop-
  • 4 carbons: But-

• Suffixes:

  • Single bonds: -ane
  • Double bonds: -ene
  • Triple bonds: -yne
  • Functional group suffixes vary (e.g., -ol for alcohol).

Chemical Properties of Carbon Compounds

Combustion Reactions

• Combustion produces carbon dioxide, heat, and light.
• Saturated hydrocarbons burn cleanly; unsaturated hydrocarbons produce soot.

Oxidation Reactions

• Alcohols can be oxidized to carboxylic acids (e.g., ethanol to acetic acid).
• Oxidizing agents add oxygen to substances.

Addition Reactions

• Unsaturated fats can be turned into saturated ones via hydrogenation (addition of hydrogen).

Substitution Reactions

• Saturated hydrocarbons react with chlorine in sunlight, replacing hydrogen with chlorine.

Important Carbon Compounds

• Ethanol (C₂H₅OH):
  • Liquid at room temperature, active in alcoholic drinks, good solvent.
• Ethanoic Acid (C₂H₄O₂):
  • Also known as acetic acid, found in vinegar, used as a preservative.

Reactions of Ethanoic Acid

• Esterification: Forms esters from alcohol and acid.
• Reactions with Bases: Forms salts from acids and bases.
• Reactions with Carbonates: Produces salts, carbon dioxide, and water.

Soaps and Detergents

• Soaps: Sodium or potassium salts with ionic and hydrophobic ends.
• Micelles help clean oily dirt by encapsulating it in water.