Organic Chemistry: Hydrocarbons, Derivatives, Nomenclature and Reactions
What you must understand
Start with carbon's tetravalency and catenation. Learn homologous series: alkanes, alkenes, alkynes, arenes, then derivatives - haloalkanes, alcohols, phenols, aldehydes, ketones, carboxylic acids, esters, amines, amides. Know functional groups and IUPAC naming: longest chain, lowest locants, suffixes and prefixes, alphabetical order.
Understand isomerism: chain, position, functional group, geometric (cis/trans, E/Z) and optical (chirality). Recognise reaction types: substitution (alkanes, arenes), addition (alkenes, alkynes), elimination (dehydration, dehydrohalogenation), oxidation and reduction, esterification, hydrolysis, polymerisation (addition and condensation). Apply Markovnikov's rule to addition and know the electrophilic addition mechanism.
Know reagents and conditions: KMnO₄ or K₂Cr₂O₇ for oxidation, H₂/Ni for hydrogenation, Br₂ for unsaturation test, Tollens' and Fehling's tests for aldehydes, NaHCO₃ for carboxylic acids.
Traps
Naming errors from wrong chain choice or wrong locants. Don't confuse aldehydes and ketones in tests - ketones fail Tollens'/Fehling's. Cis/trans needs restricted rotation (double bond or ring). Esterification is reversible and needs an acid catalyst.
Rule of thumb
Bromine water decolourises with alkenes/alkynes (addition) but not alkanes - use it to test unsaturation.
Worked example
Propan-2-ol + acidified K₂Cr₂O₇ distils to propanone (a ketone), which gives no silver mirror with Tollens' reagent.