FAD1018 Organic — Properties & Preparation
[!note] Caveman edition. No fluff. Only facts. ⭐ = exam priority (more stars = heavier weight)
Quick index:
| Section | Weight |
|---|---|
| Alcohol & Phenol | ⭐⭐⭐ |
| Carbonyl Compounds | ⭐⭐⭐ |
| Carboxylic Acids | ⭐⭐ |
| Amines | ⭐⭐ |
| Polymers | ⭐ |
Alcohol & Phenol ⭐⭐⭐
Classification
Alcohol: R-OH, OH on sp³ C. Phenol: OH directly on aromatic ring. Phenol NOT alcohol. NOT aromatic alcohol.
| Type | Structure | Oxidation product |
|---|---|---|
| 1° (primary) | R-CH₂-OH | Aldehyde → Carboxylic acid |
| 2° (secondary) | R₂CH-OH | Ketone |
| 3° (tertiary) | R₃C-OH | Resistant |
[!warning] Amine classification different Amine: R groups count on N, not C.
IUPAC Naming
- Longest chain with -OH.
- Number from end closer to -OH.
- Replace -e with -ol.
- Position number before name.
- Cyclic: C with OH = position 1.
- Multiple OH: diol, triol.
Isomerism
Structural: chain, position, functional group (alcohol vs ether).
Optical: need chiral C (4 different groups). Enantiomers rotate light opposite directions.
Physical Properties
BP discussion framework (use this order):
- H-bonding (strongest)
- Dipole-dipole
- Surface area (straight > branched)
- Molar mass
Alcohol BP >> hydrocarbon/ether at same RMM. Reason: H-bonding. Ethanol (78 °C) vs propane (−42 °C). ~120 °C gap.
1° > 2° > 3° at same RMM. Reason: surface area drop with branching.
Phenol BP > aliphatic analogue. Reason: electron delocalization strengthens intermolecular forces.
Intramolecular vs intermolecular H-bond (nitrophenols):
- 2-nitrophenol (intra): 217 °C
- 3-nitrophenol (mixed): 230 °C
- 4-nitrophenol (inter): 245 °C
Solubility:
- 1-3 C: fully soluble in water.
- 4-10 C: oily, solubility drops.
-
11 C: nearly insoluble solid.
- More -OH groups → more soluble.
- Phenol: partially soluble < 66 °C, fully soluble above.
Acidity
Alcohol weak acid. Ka = [H₃O⁺][RO⁻] / [ROH]. Higher Ka = stronger. Higher pKa = weaker.
Factors:
- Inductive: EWG on R → stabilize alkoxide → stronger acid. EDG → destabilize → weaker.
- Solvation: Bulky R → hinder alkoxide solvation → weaker acid.
pKa order: Carboxylic acid (~4.8) > Phenol (10) > Water (14) > Alcohols (15.5-18)
Within alcohols: methanol > 1° > 2° > 3°. Reason: both inductive + solvation push same direction.
| Compound | pKa |
|---|---|
| Acetic acid (ref) | 4.8 |
| Phenol | 10.0 |
| 2,2,2-Trichloroethanol | 12.2 |
| Water | 14.0 |
| Methanol | 15.5 |
| Ethanol | 15.9 |
| Isopropyl alcohol | 16.5 |
| tert-Butyl alcohol | 18.0 |
Phenol acidity: ~10⁸× more acidic than alcohols. Reason: phenoxide resonance-stabilized. Negative charge delocalized over O + 3 ring carbons.
Substituent effect on phenol pKa:
| Compound | pKa | Why |
|---|---|---|
| Phenol | 10.00 | Baseline |
| 2-Nitrophenol | 7.20 | o-NO₂ EWG, resonance puts + charge next to O |
| 4-Nitrophenol | 7.20 | p-NO₂ same |
| 3-Nitrophenol | 8.40 | m-NO₂ only -I, no resonance |
| 4-Aminophenol | 10.30 | p-NH₂ EDG, resonance puts - charge next to O |
Rule: EWG at o/p → more acidic. EDG at o/p → less acidic.
Reaction with bases: Phenol reacts with Na and NaOH. Does NOT liberate CO₂ from Na₂CO₃/NaHCO₃. Diagnostic: dissolves in NaOH, no fizz with carbonate.
Preparation — Alcohols
| Method | Reactants | Product | Notes |
|---|---|---|---|
| Fermentation | Yeast + sugars | Ethanol + CO₂ | 12-15% yield; distill to 40-50% |
| Alkene hydration | Alkene + dil H₂SO₄/H₃PO₄ | Alcohol | Markovnikov; dilute acid push equilibrium |
| Haloalkane SN | R-X + NaOH/KOH | R-OH | 1° → SN2; 3° → E2 (alkene) |
| Grignard | R-MgX + carbonyl | Alcohol | Formaldehyde → 1°; aldehyde → 2°; ketone → 3° |
| Carbonyl reduction | Aldehyde/ketone + NaBH₄/LiAlH₄ | Alcohol | Later topic |
Preparation — Phenols
Industrial: Cumene process. Benzene + propene → cumene → cumene hydroperoxide → phenol + acetone.
Lab: Aromatic amine + HNO₂ → diazonium salt + H₂O → phenol + N₂.
Identification Tests
Lucas test: conc. HCl + ZnCl₂. Cloudiness = alkyl chloride forming.
- 3°: immediate.
- 2°: 5-10 min.
- 1°: no reaction at room temp.
- Limited to <6 C alcohols.
Chromic acid test: orange Cr₂O₇²⁻ → green/blue Cr³⁺ = 1° or 2° alcohol present. No change: 3° alcohol, ketone, alkane.
Iodoform test: yellow CHI₃ precipitate. Positive: ethanol, methyl ketones, 2° alcohols oxidizable to methyl ketone. Negative: methanol, 3° alcohols.
Bromine water (phenol): decolorizes + white precipitate (2,4,6-tribromophenol).
FeCl₃ test (phenol): light purple complex. Positive for phenols and enols.
Carbonyl Compounds ⭐⭐⭐
General
C=O group. sp² hybridized. Polar bond (O electronegative). C has partial +, O has partial −. General formula: CₙH₂ₙO.
Aldehyde vs Ketone
| Feature | Aldehyde | Ketone |
|---|---|---|
| Structure | R-CHO | R-CO-R' |
| C=O position | Terminal | Internal |
| Oxidation | Easy → carboxylic acid | Resistant |
| Reactivity | More reactive | Less reactive |
| IUPAC suffix | -al | -one |
Naming
Aldehydes:
- Replace -e with -al.
- Numbering starts at carbonyl C (always position 1).
- Cyclic/aromatic: add "carbaldehyde" or use common name (benzaldehyde).
- Lower priority group → use prefix: "oxo-" for ketone O, "formyl-" for aldehyde.
Example: 4-oxohexanal (ketone + aldehyde in one molecule).
Ketones:
- Replace -e with -one.
- Number from end closer to C=O (lowest locant).
- Cyclic: C=O assumed at position 1.
- Phenyl ketones: common name with "-ophenone".
- Acetophenone (methyl phenyl ketone).
- Butyrophenone (phenyl propyl ketone).
Physical Properties
- Dipole-dipole: BP > alkane/ether.
- No H-bond donor (no O-H): BP < alcohol.
- Lower members: water-soluble.
| Compound | Type | BP |
|---|---|---|
| Propan-1-ol | Alcohol | 97 °C |
| Propanone | Ketone | 56 °C |
| Propanal | Aldehyde | 49 °C |
| Ethyl methyl ether | Ether | 11 °C |
Preparation — Aldehydes
| Method | Conditions | Notes |
|---|---|---|
| 1° alcohol oxidation | PCC/CH₂Cl₂ only. Mild. | Stops at aldehyde. Strong oxidants over-oxidize to acid. |
| Ozonolysis alkene | O₃, H₂O, Zn | Monosubstituted alkene C → aldehyde |
| Hydroformylation | Alkene + CO/H₂ | Industrial |
Preparation — Ketones
| Method | Conditions | Notes |
|---|---|---|
| 2° alcohol oxidation | Any: K₂Cr₂O₇/H⁺, CrO₃, PCC | No over-oxidation possible. |
| Ozonolysis alkene | O₃, H₂O, Zn | Disubstituted alkene C → ketone |
| Friedel-Crafts acylation | Aromatic + RCOCl + AlCl₃ | Aromatic ketone |
| Alkyne hydration | H₂O/Hg²⁺/H⁺ | Markovnikov → ketone |
Identification Tests
| Test | Aldehyde | Ketone |
|---|---|---|
| Tollens' | Silver mirror | No |
| Fehling's | Brick-red Cu₂O | No |
| Benedict's | Brick-red Cu₂O | No |
| Schiff's | Pink color | No |
| 2,4-DNP (Brady's) | Orange/red ppt | Orange/red ppt |
| Iodoform | If CH₃CHO | If methyl ketone |
[!warning] Brady's reagent = 2,4-DNPH. Only reagent for ammonia derivatives you need to know (per leaks).
Carboxylic Acids & Derivatives ⭐⭐
Structure
-COOH group (C=O + -OH on same C). sp² hybridized.
Resonance: carboxylate anion (-COO⁻) has two equivalent resonance forms → highly stable.
Naming
Replace -e with -oic acid. Examples: methanoic (formic), ethanoic (acetic), benzoic.
Physical Properties
- H-bonding: form dimers in non-polar solvents.
- Highest BP among organic classes. Reason: dimer H-bonds.
- Low members: water-soluble.
- pKa ~4-5 (much stronger than alcohols/phenols).
Acidity Factors
- EWG on R → more acidic (stabilize carboxylate).
- Resonance: delocalized negative charge over 2 O atoms → strong acid.
Preparation
| Method | Reactants | Notes |
|---|---|---|
| 1° alcohol/aldehyde oxidation | K₂Cr₂O₇/H⁺, KMnO₄/H⁺ | Strong oxidant |
| Nitrile hydrolysis | R-CN + H₂O/H⁺ | Water adds, amide intermediate |
| Grignard carboxylation | RMgX + CO₂ → RCOOMgX → H₃O⁺ → RCOOH | One C extension |
| Kolbe-Schmitt (phenol) | Phenol + CO₂/NaOH → salicylic acid | Industrial |
Derivative Reactivity Order
Acyl chloride > Acid anhydride > Ester > Acid > Amide
(Most reactive → Least. Reactivity down as leaving group quality drops.)
Derivative Physical Properties
| Derivative | BP trend | Notes |
|---|---|---|
| Acyl chloride | Lower than acid | No H-bond |
| Ester | Pleasant smell | Found in fruits, flavorings |
| Amide | Very high | Strong H-bond (N-H) |
Amines & Amino Acids ⭐⭐
Classification
Amines = NH₃ derivative. R replace H.
| Type | Formula | Example |
|---|---|---|
| 1° (primary) | RNH₂ | Methylamine |
| 2° (secondary) | R₂NH | Dimethylamine |
| 3° (tertiary) | R₃N | Trimethylamine |
| Quaternary | R₄N⁺X⁻ | Tetramethylammonium chloride |
[!note] Classification depends on R groups on N, not C.
Naming
- Prefix: amino-. Suffix: -amine.
- Examples: ethylamine, aniline (phenylamine).
Physical Properties
- H-bonding: 1° and 2° only (N-H present).
- 3° amines: no N-H → no H-bond → lowest BP.
- BP lower than comparable alcohol. Reason: N-H bond weaker than O-H.
- Characteristic fishy/amine odor.
- Solubility: low members water-soluble (H-bond with water).
- Aromatic amines: less soluble, toxic.
Basicity
Amines = base. Lone pair on N accepts H⁺. R-NH₂ + H₂O ⇌ R-NH₃⁺ + OH⁻.
Basicity order: Aliphatic 2° > Aliphatic 3° > Aliphatic 1° > NH₃ > Aromatic (aniline)
Why aniline less basic? Lone pair delocalized into aromatic ring. Less available for H⁺.
Factors:
- Alkyl groups: EDG → increase electron density on N → more basic.
- Aromatic ring: resonance delocalizes lone pair → less basic.
- Steric hindrance: 3° amines less basic than 2° in solution (solvation hindered).
Preparation
| Method | Reactants | Product | Notes |
|---|---|---|---|
| Nitro reduction | R-NO₂ + H₂/Ni or Zn/HCl | R-NH₂ | Aromatic: nitrobenzene → aniline |
| Amide reduction | R-CONH₂ + LiAlH₄ | R-CH₂NH₂ | Same C count. |
| Nitrile reduction | R-CN + LiAlH₄ | R-CH₂NH₂ | 1° only. C count +1. |
| Hoffmann degradation | R-CONH₂ + Br₂/NaOH | R-NH₂ | C count −1. Amide → amine. |
| Alkylation of NH₃ | NH₃ + R-X | Mixture | Poor method. Over-alkylation problem. |
Polymers ⭐
Key Definitions
| Term | Meaning |
|---|---|
| Monomer | Small molecule, building block |
| Polymer | Large molecule of repeating monomer units |
| Repeating unit | Basic structure repeated along chain |
| Degree of polymerization (DP) | Number of monomer units |
| Molecular weight | DP × monomer MW |
| Peptide bond | Amide linkage (−CO−NH−) |
Classification
By origin:
- Natural: proteins, cellulose, rubber, DNA
- Synthetic: nylon, PE, PVC, PS
- Semi-synthetic: rayon, cellophane
By monomer composition:
- Homopolymer: one monomer type. [-A-A-A-]ₙ.
- Copolymer: two+ monomers. Random, alternating, block, graft patterns.
By thermal behavior:
- Thermoplastic: soften on heat (reversible). PE, PP, PVC, PS.
- Thermosetting: harden permanently. Bakelite, epoxy.
By structure:
- Linear: straight chain. Can fold.
- Branched: side chains. Less crystalline.
- Cross-linked: chains joined. More elastic up to point.
- Network: extensive cross-links. Thermoset.
Recycling Codes
| Code | Polymer |
|---|---|
| 1 | PET |
| 2 | HDPE |
| 3 | PVC |
| 4 | LDPE |
| 5 | PP |
| 6 | PS |
| 7 | Other |
Key Properties
| Property | What it means |
|---|---|
| Crystallinity | Ordered regions → denser, harder, more heat-resistant |
| Tg | Glass transition. Below: rigid. Above: rubbery. |
| Tm | Crystalline regions melt |
| Tensile strength | Resistance to breaking |
| Elasticity | Return to shape after stretch |
| Plasticizer | Additive → more flexible (e.g. dibutyl phthalate in PVC) |