Chemistry
### Alcohols, Phenols and Ethers
• Lucas Test Reactivity Order — 3° > 2° > 1° alcohols with Lucas reagent (ZnCl₂/HCl). Remember "3-2-1 Blast Off" – tertiary reacts immediately (turbidity), secondary in 5 min, primary needs heating.
• Phenol Acidity Booster — Electron-withdrawing groups (NO₂, Cl) at ortho/para increase acidity; electron-donating (CH₃, OCH₃) decrease it. Mnemonic: "WD-40" – Withdrawing Dominates, Donating Opposes acidity.
• Williamson Ether Synthesis — Use alkoxide + 1° alkyl halide only. "Primary Please" – secondary/tertiary halides give elimination (alkene) instead of substitution, ruining your ether.
### Aldehydes, Ketones and Carboxylic Acids
• Tollen's vs Fehling's — Both oxidize aldehydes but not ketones. Remember "TF-Aldehydes" (True Friends). α-hydroxy ketones fool Fehling's/Benedict's due to enolization in basic medium.
• Iodoform Test Positives — CH₃CO- or CH₃CH(OH)- structures give yellow CHI₃. Mnemonic: "MEEK" – Methyl Ethyl Ketone, Ethanol, Acetaldehyde, acetophenone (Ketones with methyl adjacent to carbonyl).
• Carboxylic Acid Strength — Electron-withdrawing increases acidity. Order: CCl₃COOH > CHCl₃COOH > CH₂ClCOOH > CH₃COOH. Count chlorines: "More Chlorine, More Crime (against H⁺)".
### Organic Compounds Containing Nitrogen
• Carbylamine Test — Only 1° amines + CHCl₃ + alc. KOH give foul-smelling isocyanide. Mnemonic: "Primary Stinks" – distinguishes 1° from 2°/3° amines.
• Hinsberg's Test — 1° amines give soluble sulfonamide (base), 2° give insoluble, 3° don't react. Remember "1-Soluble, 2-Solid, 3-Silent" with benzenesulfonyl chloride.
• Diazonium Coupling — Works only at 0-5°C; above 5°C decomposes. "Ice-Cold Coupling" – keep diazonium salts cold or they decompose to phenols and N₂.
### Structure of Atom & Electronic Configurations
• Aufbau Order Trick — Diagonal rule: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d... Write (n+ℓ) values; lower (n+ℓ) fills first, if tied then lower n wins.
• Hund's Maximum Multiplicity — Fill orbitals singly before pairing. "Bus Seat Rule" – electrons prefer empty orbitals (bus seats) before doubling up.
• Chromium & Copper Exception — Cr is [Ar]3d⁵4s¹, Cu is [Ar]3d¹⁰4s¹ (not d⁴s² or d⁹s²). Half-filled/fully-filled d-subshells are extra stable: "Half or Full = Beautiful".
### Chemical Bonding and Molecular Structure
• VSEPR Geometry Count — LP + BP = steric number determines geometry. 2=linear, 3=trigonal planar, 4=tetrahedral, 5=TBP, 6=octahedral. LP repulsion: LP-LP > LP-BP > BP-BP shrinks angles.
• sp³d² Hybridization — Involves d-orbitals, needs period 3+ central atom (P, S, Cl, not N, O). "NOF (No Fluorine/Oxygen/Nitrogen) No d-orbitals" for period 2 elements.
• Bond Order Formula — BO = (bonding e⁻ − antibonding e⁻)/2. Higher BO = shorter, stronger bond. O₂ has BO=2, O₂⁺ has 2.5 (stronger/shorter than O₂).
### Coordination Compounds
• EAN Rule — Effective Atomic Number = Z − oxidation state + 2×coordination number. Stable complexes often reach nearest noble gas (EAN = 36, 54, 86).
• Crystal Field Splitting — Δₒ (octahedral) > Δₜ (tetrahedral). Remember "Octa Bigger" – octahedral splitting is larger, favors low-spin with strong-field ligands (CO, CN⁻).
• Spectrochemical Series — I⁻ < Br⁻ < Cl⁻ < F⁻ < OH⁻ < H₂O < NH₃ < en < CN⁻ < CO. Weak to strong field: "I Brought Chocolate For Our House, Where No Educated Child Comes Often."