36.1.3—Analyse

For each step in a route, identify the functional-group change, classify the reaction, name the reagent/condition and note likely by-products.

Compare the structures before and after: oxidation changes bonding to oxygen, substitution replaces a leaving group, addition consumes a π bond, and condensation removes a small molecule.

Alcohol → aldehyde with acidified dichromate is oxidation; acyl chloride + alcohol → ester is nucleophilic acyl substitution with HCl formed.

Do not classify a reaction from the reagent alone; the same reagent can behave differently with different functional groups and conditions.