Introductory organic chemistry and alkanes
Organic nomenclature, isomerism and mechanisms
Organic molecules are shown as displayed, structural or skeletal formulae. IUPAC names use the longest chain, the lowest locants and alphabetical prefixes (e.g. 2-methylbutane, 1-bromo-2-chloropropane). Structural isomers have the same molecular formula but different structures (chain, position or functional group isomers). Stereoisomers have the same structure but different spatial arrangement: E/Z isomers arise from restricted rotation about C=C when each C has two different groups. Bonds break by homolytic fission (radicals) or heterolytic fission (ions). Nucleophiles donate an electron pair; electrophiles accept one. Curly arrows show movement of electron pairs.
≈ 50 minAlkanes and free radicals
Alkanes are saturated hydrocarbons, fairly unreactive because C–C and C–H bonds are strong and non-polar. They're used as fuels: complete combustion gives CO₂ and H₂O; incomplete gives CO and soot. Cracking breaks long chains into shorter alkanes and alkenes (thermal: high T and p; catalytic: zeolite, lower T). With Cl₂ or Br₂ in UV light, alkanes undergo free-radical substitution: initiation (), propagation (; ), termination (two radicals join). The mixture of products is a disadvantage. Cl• radicals from CFCs destroy ozone catalytically.
≈ 45 min