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Oxidation and dehydration are the two most tested alcohol reactions in JEE.

Oxidation: 1° alcohol -> aldehyde (PCC, mild) or carboxylic acid (KMnO4, Jones). 2° alcohol -> ketone (any oxidant). 3° alcohol -> resistant (no C-H on carbinol C). PCC is the key reagent for stopping at aldehyde — it works in anhydrous CH2Cl2, preventing over-oxidation.

Dehydration: ROH + conc. H2SO4 + heat -> alkene + H2O. Ease: 3° > 2° > 1° (follows carbocation stability). Zaitsev's rule: more substituted alkene is the major product. Critical detail: ethanol at 170°C gives ethene (intramolecular); at 140°C gives diethyl ether (intermolecular).

Carbocation rearrangements during dehydration are common and heavily tested. Example: neopentyl alcohol (1°) dehydrates to 2-methylbut-2-ene via a methyl shift to form a 3° carbocation. The POCl3/pyridine (Chugaev) method avoids rearrangement by proceeding through a cyclic transition state without carbocation formation.

The Victor Meyer test distinguishes all three classes: 1° gives blood-red, 2° gives blue, 3° gives no colour. Lucas test $\frac{ZnCl2}{HCl}$: 3° instant turbidity, 2° in 5-10 min, 1° no reaction at RT.