Polyhalogen Compounds – Ready-to-Read Notes 😊

When a carbon chain grabs two or more halogen atoms, the result is a polyhalogen compound. These molecules power paint removers, fridges, and even malaria control—yet many also hurt our health 💔 and our planet 🌍.

1. Dichloromethane – CH2Cl2 (Methylene chloride) 🧽

  • Star uses: Paint-stripper, aerosol propellant, metal-cleaner, and solvent in drug production. :contentReference[oaicite:0]{index=0}
  • Health alerts: Small whiffs dull hearing and vision, larger breaths cause dizziness, nausea, and finger-tingling. Skin or eye contact gives a sharp burn. :contentReference[oaicite:1]{index=1}

2. Trichloromethane – CHCl3 (Chloroform) 🛌

  • Main job today: Feedstock for refrigerant R-22; still a handy solvent for fats and alkaloids. :contentReference[oaicite:2]{index=2}
  • Health story: About 900 ppm in air leads to dizziness and fatigue; long exposure can damage liver and kidneys. :contentReference[oaicite:3]{index=3}
  • Safety tip: Air + light slowly turn chloroform into deadly phosgene (COCl2), so chemists store it in full, dark bottles. :contentReference[oaicite:4]{index=4}

3. Triiodomethane – CHI3 (Iodoform) 🩹

  • Worked as an antiseptic thanks to free iodine release, but its strong smell forced a switch to friendlier iodine formulas. :contentReference[oaicite:5]{index=5}

4. Tetrachloromethane – CCl4 (Carbon tetrachloride) 🧯

  • Industrial roles: Once popular as a refrigerator fluid, dry-cleaning agent, and fire extinguisher additive. :contentReference[oaicite:6]{index=6}
  • Toxic hits: Dizziness, nausea, nerve damage; can stop the heartbeat and irritate eyes. :contentReference[oaicite:7]{index=7}
  • Planet impact: Escapes to the stratosphere and eats away ozone, raising UV-B exposure and skin-cancer risk. :contentReference[oaicite:8]{index=8}

5. Freons – Chlorofluorocarbons (CFCs) ❄️

  • Freon 12 (CCl2F2) tops the list; non-toxic, non-corrosive, and once beloved in aerosol cans and AC units. :contentReference[oaicite:9]{index=9}
  • Making Freon 12:

\( \mathrm{CCl_4 + 2HF \xrightarrow{\text{SbF}_5} CCl_2F_2 + 2HCl} \)  ✨ (Swarts reaction) :contentReference[oaicite:10]{index=10}

  • Billions of pounds produced by 1974! Most drift up to the stratosphere, sparking radical chains that thin ozone. :contentReference[oaicite:11]{index=11}

6. DDT – p,p′-Dichlorodiphenyltrichloroethane 🦟

  • Prepared in 1873 but fame struck in 1939 when Paul Müller proved its mosquito-killing power, earning the 1948 Nobel 🏆. :contentReference[oaicite:12]{index=12}
  • Heavy post-WWII use slashed malaria yet sparked resistance in insects and showed high fish toxicity. :contentReference[oaicite:13]{index=13}
  • DDT dissolves in fat, so it builds up in animals; the USA banned it in 1973, though some regions still rely on it. :contentReference[oaicite:14]{index=14}

High-Yield NEET Nuggets 🔥

  1. Swarts reaction converts CCl4 to Freon 12—know the reagents (HF + SbF5). :contentReference[oaicite:15]{index=15}
  2. Phosgene danger: Light oxidises chloroform to COCl2; storage precautions are exam-friendly. :contentReference[oaicite:16]{index=16}
  3. Ozone trouble: CFCs and CCl4 reach the stratosphere and start radical chains that deplete ozone. :contentReference[oaicite:17]{index=17}
  4. Bioaccumulation of DDT—fat-soluble, persistent, banned in many nations. :contentReference[oaicite:18]{index=18}
  5. Health hits of CH2Cl2 & CHCl3—central-nervous-system depression and organ toxicity crop up often in questions. :contentReference[oaicite:19]{index=19}

✨ Happy studying! You’ve got this! ✨