Organic Chemistry: Nomenclature, Isomerism and Reaction Mechanisms
Organic Chemistry: Nomenclature, Isomerism and Reaction Mechanisms tests IUPAC naming, structural and stereoisomerism, electronic effects, and the SN1, SN2, E1, and E2 pathways.
Core rules
- Select the longest carbon chain containing the principal functional group; number to give the lowest locant set; cite substituents alphabetically.
- Functional-group priority determines the suffix: carboxylic acid > ester > amide > aldehyde > ketone > alcohol > amine > alkene > alkyne.
- Isomerism includes chain, position, functional, geometric, and optical forms. A chiral carbon has four different groups.
- Inductive effects operate through sigma bonds; resonance operates through pi systems; hyperconjugation stabilizes carbocations and alkenes.
- SN2 is one-step, bimolecular, and favored by methyl/primary substrates and strong nucleophiles. SN1 is two-step, favored by tertiary substrates and polar protic solvents, and gives racemization at a chiral center.
Worked example
Hydrolysis of 2-bromo-2-methylpropane in aqueous ethanol is SN1. The tertiary C–Br bond ionizes slowly to a tertiary carbocation, which is stabilized by three alkyl groups through induction and hyperconjugation. Water then attacks the carbocation. The rate depends on the substrate concentration, not on the nucleophile concentration, so rate = k[substrate].
Traps
Do not choose a chain that excludes the principal functional group. Do not number from the end that gives the first substituent if that violates the lowest locant set for the principal group. Do not confuse E2 with SN2; E2 uses a strong base and forms a pi bond. Do not ignore stereochemistry in SN1 and SN2 products.