Chapter 4: Carbon and its Compounds

Introduction to Carbon

• Unique Features:
  • Carbon has four valence electrons, allowing it to form covalent bonds with other atoms.
  • It can form single, double, or triple bonds, leading to a vast array of compounds.
  • Carbon atoms can bond with each other to form long chains, branched chains, or rings.

Covalent Bonding in Carbon Compounds

• Covalent Bonds: Sharing of electrons to achieve a stable electronic configuration.
• Types:
  • Single Bond: Sharing one pair of electrons (e.g., methane, CH₄).
  • Double Bond: Sharing two pairs (e.g., ethene, C₂H₄).
  • Triple Bond: Sharing three pairs (e.g., ethyne, C₂H₂).

Allotropes of Carbon

• Diamond:
  • Each carbon atom is bonded to four others in a tetrahedral arrangement; hard, transparent, insulator.
• Graphite:
  • Carbon atoms arranged in layers of hexagons; each atom bonded to three others; good conductor due to free electrons, soft, used in pencils.
• Fullerenes:
  • Spherical or cylindrical structures (e.g., C₆₀ or buckminsterfullerene); new form of carbon with potential applications in nanotechnology.
• Graphene:
  • Single layer of graphite; extremely strong, conducts electricity, potential in electronics.

Versatile Nature of Carbon

• Catenation: Ability of carbon atoms to link with one another to form chains or rings.
• Tetravalency: Four valence electrons allow for a variety of bonding possibilities.
• Isomerism: Compounds with the same molecular formula but different structural formulas.

Hydrocarbons

• Saturated: Single carbon-carbon bonds only (Alkanes, e.g., Methane CH₄).
• Unsaturated:
  • Alkenes: Contain at least one double bond (E.g., Ethene C₂H₄).
  • Alkynes: Contain at least one triple bond (E.g., Ethyne C₂H₂).

Functional Groups

• Alcohols: -OH group (e.g., Ethanol - C₂H₅OH).
• Aldehydes: -CHO group (e.g., Formaldehyde - HCHO).
• Ketones: >CO group (e.g., Acetone - CH₃COCH₃).
• Carboxylic Acids: -COOH group (e.g., Acetic acid - CH₃COOH).
• Halogen Derivatives: When hydrogen in hydrocarbons is replaced by halogens (e.g., Chloromethane - CH₃Cl).

Nomenclature

• IUPAC Naming: Systematic way to name organic compounds based on the longest carbon chain, functional groups, and substituents.

Chemical Properties

• Combustion: Carbon compounds burn in air to produce CO₂, H₂O, and energy.
• Oxidation: Reaction with oxygen or oxidizing agents to form compounds like alcohols or carboxylic acids.
• Addition Reactions: Common in unsaturated hydrocarbons; e.g., hydrogenation of ethene to ethane.
• Substitution Reactions: Common in saturated hydrocarbons; e.g., methane with chlorine to form chloromethane.
• Esterification: Reaction between an alcohol and a carboxylic acid to form an ester, with water as a byproduct.

Ethanol and Ethanoic Acid

• Ethanol (C₂H₅OH):
  • Preparation: By hydration of ethene or fermentation of sugars.
  • Uses: Solvent, fuel (biofuel), in alcoholic beverages, antiseptic.
  • Properties: Flammable, liquid at room temperature, can denature proteins.
• Ethanoic Acid (CH₃COOH):
  • Preparation: Oxidation of ethanol.
  • Uses: Vinegar (dilute solution), in making esters, preservatives.
  • Properties: Acidic, pungent smell, corrosive to metals.

Soaps and Detergents

• Soaps: Sodium or potassium salts of long-chain fatty acids; work by micelle formation to remove dirt.
• Detergents: Synthetic substitutes; can be used in hard water; less biodegradable than soaps.

Carbon: Environmental Impact

• Carbon Cycle: Essential for life, involves photosynthesis, respiration, decomposition, and fossil fuel burning.
• Greenhouse Gases: CO₂ from burning fossil fuels contributes to global warming.

Conclusion

• Carbon's ability to form a vast array of compounds underpins much of organic chemistry, influencing everything from biology to material science. Understanding carbon compounds is crucial for technological advancement, environmental management, and daily life applications.