$word_{count}$: 230

Wurtz reaction: 2RX + 2Na (dry ether) → R-R + 2NaX. Couples two alkyl halides. Works best for identical 1 degree halides. Cross-coupling gives mixtures. Fails for 3 degree (elimination dominates).

Wurtz-Fittig reaction: ArX + RX + 2Na → Ar-R + 2NaX. Cross-couples aryl with alkyl. Better selectivity than pure Wurtz because ArX doesn't self-couple easily.

Fittig reaction: 2ArX + 2Na → Ar-Ar (biphenyl). Aryl-aryl coupling.

Finkelstein reaction: RCl + NaI (acetone) → RI + NaCl. Driven by precipitation of NaCl from acetone.

Swarts reaction: RCl + AgF → RF + AgCl. Converts chloride to fluoride (used for freon synthesis).

Grignard reagent: RX + Mg (dry ether) → RMgX. Versatile organometallic for C-C bond formation.

Sandmeyer reaction: $ArN2^+$ + CuX → ArX + N2 (X = Cl, Br, CN). Via diazonium salt.

Key applications: DDT = condensation of PhCl with CCl3CHO (H2SO4 catalyst). BHC/Lindane = C6H6 + 3Cl2 (UV, radical addition). Freons (CFCs like CCl2F2) = refrigerants, now banned (ozone depletion). CCl4 = historic fire extinguisher (toxic — produces phosgene).