Rucete ✏ SAT Chemistry In a Nutshell
14. Carbon and Organic Chemistry
This chapter introduces the chemistry of carbon and its compounds—especially hydrocarbons and their functional derivatives. You'll learn about carbon’s bonding behavior, structural formulas, naming conventions, isomerism, and functional groups essential for SAT Chemistry.
Carbon and Its Allotropes
- Carbon occurs in several allotropic forms:
- Diamond: sp³ bonded; extremely hard and high melting point
- Graphite: sp² bonded layers; slippery and conducts electricity
- Amorphous: includes charcoal, coke, lampblack
- Fullerenes: spherical C₆₀-like structures
Carbon Dioxide (CO₂)
- 0.04% of air; part of the natural CO₂ cycle
- Lab prep: CaCO₃ + HCl → CaCl₂ + CO₂ + H₂O
- Test: Turns limewater cloudy (CaCO₃ formation)
- Uses:
- Forms carbonic acid in sodas
- Dry ice used for refrigeration
- Used in fire extinguishers
- Consumed during photosynthesis
Introduction to Organic Chemistry
- Study of carbon-containing compounds, especially with C–H bonds
- Carbon forms 4 covalent bonds → chains, rings, branches
- Most are nonpolar, with low melting/boiling points, and are poor conductors
Hydrocarbons
- Hydrocarbons: made of only carbon and hydrogen
Alkanes (Saturated Hydrocarbons)
- Contain only single bonds
- Formula: CₙH₂ₙ₊₂
- Names end in -ane (e.g., methane, ethane, propane)
- Combustion example: CH₄ + 2O₂ → CO₂ + 2H₂O + heat
Alkenes (Unsaturated)
- Contain double bonds (C=C)
- Formula: CₙH₂ₙ
- Names end in -ene (e.g., ethene, propene)
- More reactive than alkanes
Alkynes
- Contain triple bonds (C≡C)
- Formula: CₙH₂ₙ₋₂
- Names end in -yne (e.g., ethyne)
- Even more reactive than alkenes
Aromatic Hydrocarbons
- Based on benzene ring (C₆H₆)
- Undergo substitution reactions, not addition
- Example: toluene (methylbenzene)
Isomerism
- Isomers: same formula, different structure
- Structural isomers: different bonding
- Geometric isomers: cis/trans in alkenes
Functional Groups and Organic Families
Organic compounds are categorized based on their functional groups.
- Alcohols (R–OH): hydroxyl group, ends in -ol, hydrogen bonding
- Aldehydes (R–CHO): terminal carbonyl, ends in -al
- Ketones (R–CO–R’): internal carbonyl, ends in -one
- Carboxylic Acids (R–COOH): carboxyl group, ends in -oic acid, weak acids
- Esters (R–COOR’): sweet-smelling, ends in -oate
- Ethers (R–O–R’): solvents, named as alkyl + ether
- Amines (R–NH₂): contain nitrogen, basic, end in “amine”
- Amino Acids: have –NH₂ and –COOH, building blocks of proteins
Types of Organic Reactions
- Substitution: atom/group replaces another (alkanes, aromatics)
- Addition: added to double/triple bonds (alkenes, alkynes)
- Polymerization: monomers → polymers (e.g., ethene → polyethylene)
- Fermentation: sugars → ethanol + CO₂
- Esterification: acid + alcohol → ester + water (e.g., CH₃COOH + CH₃OH)
- Saponification: fat + base → soap + glycerol
- Combustion: hydrocarbon + O₂ → CO₂ + H₂O + energy
In a Nutshell
Carbon’s ability to form stable chains and rings results in a vast organic world. Hydrocarbons are foundational, and functional groups define reactivity. Understanding key reactions like substitution and polymerization is essential for real-world chemistry and SAT success.