1851 — Alexander Williamson synthesizes diethyl ether from diethyl sulfate + ethoxide
       → Establishes Williamson Ether Synthesis principle (SN2 mechanism)

1860 — Hermann Kolbe discovers carboxylation of sodium phenoxide with $CO_{2}$
       → Kolbe (Kolbe-Schmitt) Reaction: produces salicylic acid

1876 — Karl Ludwig Reimer and Ferdinand Tiemann discover formylation of phenol
       → Reimer-Tiemann Reaction: $CHCl_{3}$/NaOH gives salicylaldehyde via :$CCl_{2}$

1880s — Salicylic acid used as antiseptic and pain reliever
        → Led directly to Bayer synthesizing aspirin (acetylsalicylate) in 1897

1975 — E.J. Corey and W.L. Mock develop PCC (pyridinium chlorochromate)
       → Selective mild oxidant for 1° alcohol → aldehyde without over-oxidation

NEET Context:
All five reactions (Williamson, Kolbe, Reimer-Tiemann, Lucas test, PCC oxidation)
are explicitly in the CBSE Class 12 curriculum and appear regularly in NEET papers.