Organic Chemistry and Polymer Materials
Organic chemistry and polymer materials tests functional-group chemistry, nomenclature and the link between monomer structure and polymer properties. Expect reaction-type identification and simple polymer calculations.
Functional groups and naming
Alkanes (C–C), alkenes (C=C), alcohols (–OH), aldehydes (–CHO), ketones (>C=O), carboxylic acids (–COOH), esters (–COO–) and amines (–NH₂) each have characteristic tests and reactions. Name the longest chain, number from the end giving the lowest locants, and cite substituents alphabetically.
Reaction types
Alkenes undergo addition with H₂, Br₂, HCl or H₂O; alkanes undergo substitution with halogens under UV; alcohols are oxidised to aldehydes, ketones or acids; carboxylic acids and alcohols form esters with a concentrated acid catalyst.
Polymers
Addition polymerisation joins monomers containing C=C without losing any atom, so the repeat unit has the same formula as the monomer. Condensation polymerisation loses a small molecule such as water; polyesters and polyamides form this way. Thermoplastics soften on heating; thermosetting polymers have cross-links and do not.
Worked example
A PVC sample has molar mass 62 500 g mol⁻¹; the monomer C₂H₃Cl has M = 62.5 g mol⁻¹. Degree of polymerisation = 62 500/62.5 = 1000.
Traps
Drawing a repeat unit with the double bond still present, confusing addition and condensation polymers, and failing to distinguish an aldehyde from a ketone with Tollens' reagent.