ONE-PAGE REVISION: OC-11 POLYMERS & ENVIRONMENTAL CHEMISTRY
TOP 5 NEET TRAPS (memorize before the exam)
- HDPE = ZN catalyst + LOW P (linear). LDPE = radical + HIGH P (branched). [These are ALWAYS swapped in traps]
- Normal rain pH = 5.6 (NOT 7). Acid rain = pH < 5.6.
- Nylon-6,6 = 2 monomers (HMD + adipic acid). Nylon-6 = 1 monomer (caprolactam). [NOT reversed]
- Minamata = Hg (Mercury). Itai-Itai = Cd (Cadmium). [NOT reversed]
- Cl• is CATALYTIC — one Cl• destroys ~100,000 O3 molecules (NOT consumed).
ADDITION POLYMERS (no byproduct, same formula as monomer)
| Polymer | Monomer SMILES | Conditions | Property |
|---|---|---|---|
| HDPE | C=C | ZN cat, low P | Linear, dense, strong |
| LDPE | C=C | Free radical, 1000–2000 atm | Branched, flexible |
| PVC | C=CCl | Free radical | Pipes, cables |
| Teflon | FC(F)=C(F)F | Free radical | Inert, non-stick |
| Polystyrene | C=Cc1ccccc1 | Free radical | Packaging |
| PAN (Orlon) | C=CC#N | Free radical | Synthetic wool |
CONDENSATION POLYMERS (lose H2O, bifunctional monomers)
| Polymer | Monomer(s) | Linkage | Thermal |
|---|---|---|---|
| Nylon-6,6 | HMD (NCCCCCCN) + Adipic acid (OC(=O)CCCCC(=O)O) | –CO–NH– | Thermoplastic |
| Nylon-6 | Caprolactam (O=C1CCCCCN1) ring-open | –CO–NH– | Thermoplastic |
| Dacron/PET | EG (OCCO) + TPA (OC(=O)c1ccc(C(=O)O)cc1) | –COO– | Thermoplastic |
| Bakelite | Phenol + HCHO | C–C (cross-linked) | Thermosetting |
RUBBER KEY FACTS
- Natural rubber = cis-1,4-polyisoprene (isoprene:
C=CC(=C)C) — elastic - Gutta-percha = trans-1,4-polyisoprene — hard, non-elastic
- Vulcanization: rubber + 2–3% S + heat → S–S cross-links → harder + more elastic
- Buna-S: butadiene + styrene (tires). Buna-N: butadiene + acrylonitrile (oil-resistant)
ENVIRONMENTAL CHEMISTRY NUMBERS TO MEMORIZE
| Fact | Value |
|---|---|
| Normal rain pH | 5.6 |
| Acid rain pH | < 5.6 |
| Clean water BOD | < 5 ppm |
| Polluted water BOD | > 17 ppm |
| O3 molecules destroyed per Cl• | ~100,000 |
| Sulfur used in vulcanization | 2–3% |
| LDPE pressure | 1000–2000 atm |
| LDPE temperature | 350–570 K |
SMOG COMPARISON
| Feature | London Smog | Photochemical Smog |
|---|---|---|
| Conditions | Cold, humid | Warm, sunny |
| Key pollutants | SO2 + particulates | NO2 + VOCs → O3 + PAN |
| Nature | Reducing | Oxidizing |
| Effect | Respiratory, visibility | Eye irritation, plant damage |
HEAVY METAL DISEASES
- Hg → Minamata (neurological, Japan). Cd → Itai-Itai (bone pain, Japan). Pb → neurological damage.
OZONE DEPLETION SUMMARY
CFC --[UV stratosphere]--> Cl•; Cl• + O3 → ClO• + O2; ClO• + O• → Cl• + O2; Net: O3 + O• → 2O2. Cl• is the catalyst.
GREEN CHEMISTRY
- Prevention over cure; Atom economy = × 100%.
- H2O2 = clean oxidant (only byproduct = H2O). 100% atom economy for addition reactions.