Hybridization in Practice
- Polyethylene (PE): Made from ethylene (CH2=CH2, sp2 carbon). Addition polymerization converts sp2 carbons to sp3, creating long -[CH2-CH2]n- chains used in bottles, bags, pipes.
- Acetylene welding: HC≡CH (sp carbon) burns at ~3500°C in oxy-acetylene torches — the high bond strength of C≡C requires intense heat to break.
- Natural gas (methane, sp3): Burns cleanly in kitchen stoves. The sp3 C-H bonds break homolytically in combustion.
Electronic Effects in Daily Life
- Aspirin (acetylsalicylic acid): Contains both -OH (as ester) and -COOH groups. The -COOH group makes aspirin acidic — useful as an anti-inflammatory.
- Vinegar (ethanoic acid): CH3COOH, pKa 4.75. The +I methyl group makes it a weak acid — household safe.
- Trichloroacetic acid (TCA): CCl3COOH, pKa 0.7 (100× stronger than acetic acid). Used as a chemical peel in cosmetic dermatology — demonstrates -I effect of three Cl atoms.
Isomerism in Medicine
- Optical isomers (enantiomers) in drugs: L-DOPA (L-enantiomer) is used for Parkinson's disease; D-DOPA is inactive or harmful. The chiral center at C-2 (bonded to NH2, OH, aromatic ring, and H) determines pharmacological activity.
- Thalidomide: One enantiomer is a sedative; the other causes birth defects. This disaster in the 1950s established the critical importance of optical isomerism in pharmaceuticals.
Industrial Organic Chemistry
- Ethylene glycol (HOCH2CH2OH, SMILES:
OCCO): Antifreeze — contains two -OH groups. sp3 carbon throughout. - Acetone (propanone, SMILES:
CC(=O)C): Industrial solvent. sp2 carbonyl carbon. The ketone functional group makes it polar and miscible with water.