Alcohols are classified as primary, secondary, or tertiary based on the number of alkyl groups on the hydroxyl-bearing carbon, and this determines their behaviour in oxidation, dehydration, and Lucas test reactions. PCC is a mild, selective oxidant that stops the oxidation of primary alcohols at the aldehyde stage, while $KMnO_{4}$ and $K_{2}Cr_{2}O_{7}$ are strong oxidants that carry the reaction all the way to carboxylic acid. Secondary alcohols are oxidized to ketones by any oxidant; tertiary alcohols resist oxidation entirely because they lack a hydrogen on the carbinol carbon. The Lucas test uses $ZnCl_{2}$ in concentrated HCl and distinguishes alcohol types by turbidity: tertiary gives immediate turbidity, secondary in 5-20 minutes, and primary shows no turbidity at room temperature. Phenol is far more acidic than alcohols (pKa ~10 vs ~16-18) because the phenoxide ion is stabilized by resonance delocalization of the negative charge over the benzene ring through five resonance structures. Electron-withdrawing groups such as -$NO_{2}$ on the ring increase phenol's acidity, while electron-donating groups such as -$CH_{3}$ decrease it. The Kolbe reaction converts sodium phenoxide with $CO_{2}$ under pressure to salicylic acid (ortho-carboxylation), and the Reimer-Tiemann reaction converts phenol with $CHCl_{3}$/NaOH to salicylaldehyde (ortho-formylation) via the electrophilic intermediate dichlorocarbene. Phenol reacts with bromine water directly to give 2,4,6-tribromophenol without any Lewis acid catalyst, in contrast to benzene which requires $FeBr_{3}$. Ethers are most reliably prepared by Williamson synthesis, an SN2 reaction between an alkoxide and a primary alkyl halide; secondary and tertiary halides must be avoided because they give E2 elimination with the strong alkoxide base. Excess HI cleaves ethers to give two alkyl iodides, since the first equivalent of HI converts the ether to an alcohol and alkyl iodide, and the second converts the alcohol to a second alkyl iodide.