(i) Pentan-2-ol   (ii) 3-methylbutan-2-ol   (iii) 2-methylpropan-2-ol   (iv) Propane-1,2-diol   (v) Ethoxybenzene (phenetole)   (vi) 2-methoxypropane   (vii) 2,4-dinitrophenol   (viii) 3-methylphenol (m-cresol).

(i) (CH₃)₂C(OH)CH₂CH₃   (ii) C₆H₅CH₂CH(OH)CH₃   (iii) (CH₃)₂C(OH)CH₂C(OH)(CH₃)CH₂CH₂OH   (iv) 2,3-diethylphenol: benzene with –OH at C-1, –C₂H₅ at C-2 and –C₂H₅ at C-3   (v) CH₃CH₂OCH₂CH₂CH₃   (vi) CH₃CH₂–O–CH(CH₃)–CH(C₂H₅)–CH₂CH₃   (vii) C₆H₁₁–CH₂OH (cyclohexyl-CH₂OH)   (viii) (C₂H₅)₂C(OH)–C₆H₁₁ (two ethyls and one cyclohexyl on the C-OH).

Eight isomers: 1. pentan-1-ol (1°); 2. pentan-2-ol (2°); 3. pentan-3-ol (2°); 4. 2-methylbutan-1-ol (1°); 5. 3-methylbutan-1-ol (1°); 6. 2-methylbutan-2-ol (3°); 7. 3-methylbutan-2-ol (2°); 8. 2,2-dimethylpropan-1-ol (neopentyl alcohol, 1°).

Propan-1-ol (b.p. 97 °C) has an –OH group, so its molecules form extensive intermolecular hydrogen bonds in the liquid. Butane (b.p. –0.5 °C) has only weak London dispersion forces. Breaking the H-bond network in propan-1-ol requires much more energy, so its boiling point is far higher even though butane has a slightly larger molar mass.

The –OH group of an alcohol donates and accepts hydrogen bonds to water, fitting into water's H-bond network. Hydrocarbons cannot H-bond; they only interact by weak dispersion forces and are squeezed out of the water network (the "hydrophobic effect"). As the alkyl chain length increases, the hydrocarbon part dominates and solubility falls — from miscible (C1–C4) to essentially insoluble (≥ C10).

Alkene + B₂H₆/THF gives a trialkylborane (syn-addition, boron on less hindered C); alkaline H₂O₂ replaces B by OH with retention. Net effect: anti-Markovnikov syn-hydration of the alkene, giving a 1° alcohol from a terminal alkene.

Three monohydric phenols (cresols) + one non-phenol isomer (benzyl alcohol, not a phenol): 2-methylphenol (o-cresol), 3-methylphenol (m-cresol), 4-methylphenol (p-cresol). Benzyl alcohol C₆H₅CH₂OH also has the formula C₇H₈O but is an alcohol, not a phenol.

o-nitrophenol is steam-volatile. It forms an intramolecular hydrogen bond (chelation) between the –OH and the adjacent –NO₂, existing as discrete molecules with low intermolecular association and high vapour pressure. p-nitrophenol can only H-bond intermolecularly, forming an associated polymeric structure with very low volatility.

Both phenol and acetone are commercially valuable — this is the industrial route for ~90% of world phenol.

The extreme conditions are needed because the C(aryl)–Cl bond has partial double-bond character and resists nucleophilic substitution. This is known as the Dow process.

Three steps: (1) Protonation of the π bond: CH₂=CH₂ + H⁺ → CH₃–CH₂⁺ (ethyl cation). (2) Nucleophilic attack by water on the carbocation: CH₃CH₂⁺ + H₂O → CH₃CH₂–O⁺H₂. (3) Deprotonation of the oxocarbenium: CH₃CH₂–O⁺H₂ → CH₃CH₂OH + H⁺ (catalyst regenerated).

(i) Styrene + dilute H₂SO₄ (Markovnikov) → C₆H₅CH(OH)CH₃ (1-phenylethanol). (ii) C₆H₁₁–CH₂Br → C₆H₁₁–CH₂MgBr (Mg/ether) → + HCHO → + H₃O⁺ → C₆H₁₁–CH₂–CH₂OH? Wait — one more C. To get cyclohexylmethanol directly: C₆H₁₁–MgBr + HCHO → C₆H₁₁–CH₂OH (cyclohexylmethanol). Starting alkyl halide = cyclohexyl bromide. (iii) Pentan-1-ol via Grignard: C₄H₉–Br → C₄H₉–MgBr → + HCHO → + H₃O⁺ → CH₃(CH₂)₃CH₂OH (pentan-1-ol).

(a) Phenol + NaOH → sodium phenoxide + H₂O (ethanol does not react with NaOH). (b) Phenol + Na → sodium phenoxide + ½ H₂ (ethanol also reacts, but much more slowly). Acidity: phenol (pKa ≈ 10) >> ethanol (pKa ≈ 16) — a factor of ~10⁶. The phenoxide ion is stabilised by delocalisation of the negative charge into the aromatic ring, whereas the ethoxide has the charge localised on oxygen.

(i) –NO₂ is electron-withdrawing (–M, –I); at the ortho position it strongly stabilises the phenoxide anion by resonance, increasing acidity (pKa ~7.2). –OCH₃ is electron-donating (+M); it destabilises the phenoxide, decreasing acidity (pKa ~9.9). (ii) The –OH oxygen has lone pairs that delocalise into the ring, producing resonance structures with negative charges at ortho and para carbons. This makes the ring more nucleophilic toward electrophiles and directs them to the ortho/para positions.

(i) C₆H₅ONa + CO₂ → (400 K, 7 atm) → o-HO–C₆H₄–COONa → H⁺ → salicylic acid. (ii) C₆H₅OH + CHCl₃ + 3 NaOH → o-HO–C₆H₄–CHO + 3 NaCl + 2 H₂O (salicylaldehyde). (iii) CH₃–CH₂–O⁻Na⁺ + CH₃–I → CH₃CH₂–O–CH₃ + NaI (methoxyethane). (iv) C₆H₅OH + Zn (distil) → C₆H₆ + ZnO (reduction of phenol to benzene).

(i) Kolbe: sodium phenoxide reacts with CO₂ (400 K, 7 atm) to give ortho-hydroxybenzoic acid (salicylic acid) after acidification. Precursor to aspirin. (ii) Reimer–Tiemann: phenol + CHCl₃ in NaOH(aq) → salicylaldehyde via a dichlorocarbene (:CCl₂) attacking the ortho position; hydrolysis of the intermediate benzal chloride gives the aldehyde. (iii) Williamson: an alkoxide RO⁻ displaces X from a primary alkyl halide R'X (SN2) to give the ether R–O–R'. E.g. C₂H₅ONa + CH₃I → CH₃–O–C₂H₅. (iv) Unsymmetrical (mixed) ether has two different R groups on oxygen, e.g. methoxyethane CH₃–O–C₂H₅.

Heat propan-1-ol with conc. H₂SO₄ at 413 K (intermolecular dehydration): Mechanism (SN2): (1) Protonation of one alcohol: CH₃CH₂CH₂–OH + H⁺ → CH₃CH₂CH₂–OH₂⁺. (2) Second alcohol's O attacks the carbon, expelling water: CH₃CH₂CH₂–OH + CH₃CH₂CH₂–OH₂⁺ → CH₃CH₂CH₂–O⁺(H)–CH₂CH₂CH₃ + H₂O. (3) Deprotonation: → 1-propoxypropane (dipropyl ether) + H⁺.

For 2° and 3° alcohols, the intermediate carbocation is stable and preferentially loses a β-proton to form the alkene (elimination) rather than being captured by a second alcohol molecule (substitution). Also, steric crowding around the more substituted carbon hinders nucleophilic attack by the second alcohol. Net result: alkene dominates even at 413 K, and yield of ether is poor.

Three steps (E1/E2 hybrid): (1) Protonation of –OH: CH₃CH₂OH + H⁺ → CH₃CH₂–OH₂⁺ (good leaving group). (2) Loss of water and simultaneous loss of a β-H: the concerted E2 pathway gives CH₂=CH₂ directly. (For 3° alcohols a discrete carbocation (E1) forms first; for 1° alcohols like ethanol, the mechanism is effectively concerted E2.) (3) Final products: ethene + H₃O⁺ (catalyst regenerated). Conditions: conc. H₂SO₄, 443 K. (At 413 K the ether, not the alkene, is the major product.)

(i) CH₃CH=CH₂ + H₂O/H⁺ (dilute H₂SO₄) → CH₃CH(OH)CH₃ (Markovnikov). (ii) C₆H₅CH₂Cl + aq. NaOH → C₆H₅CH₂OH + NaCl. (iii) C₂H₅MgCl + HCHO → C₂H₅CH₂OMgCl → H₃O⁺ → CH₃CH₂CH₂OH (propan-1-ol). (iv) 2 CH₃MgBr + CH₃COCH₃ (acetone): actually one equivalent is enough — CH₃MgBr + (CH₃)₂C=O → (CH₃)₃C–OMgBr → H₃O⁺ → (CH₃)₃C–OH (2-methylpropan-2-ol).

(i) Acidified KMnO₄ or K₂Cr₂O₇/H₂SO₄. (ii) PCC (pyridinium chlorochromate) in CH₂Cl₂. (iii) Bromine in water (aq. Br₂). (iv) Acidified KMnO₄. (v) Conc. H₂SO₄ at 443 K (or Al₂O₃, 623 K). (vi) NaBH₄ in methanol (or LiAlH₄, or H₂/Ni).

(i) –NO₂ is strongly electron-withdrawing (–M, –I). At ortho or para, it delocalises the phenoxide's negative charge onto the –NO₂ oxygen, adding extra stabilisation and lowering pKa (phenol 10.0 → 4-nitrophenol 7.15 → 2-nitrophenol 7.23). (ii) Alcohols H-bond with water; hydrocarbons cannot. (iii) The C(sp²)–O bond of phenol has partial double-bond character (resonance with ring) and resists nucleophilic substitution. Even with HCl the –OH is not displaced by Cl under ordinary conditions — unlike in an alcohol, where protonation followed by SN1/SN2 readily gives R–Cl.

–NO₂ at the ortho position withdraws electrons by both inductive (–I) and resonance (–M) effects; it stabilises the phenoxide anion, making ortho-nitrophenol a stronger acid (pKa ≈ 7.2). –OCH₃ donates electrons by resonance (+M); it destabilises the phenoxide of ortho-methoxyphenol, making it a weaker acid (pKa ≈ 9.9) than even phenol.

The oxygen lone pair is donated into the π system, producing resonance structures with negative charges at the ortho and para carbons. This raises the HOMO energy and increases electron density at those positions, making phenol much more nucleophilic toward electrophiles than benzene itself (roughly 10³–10⁶ times faster). The same resonance also explains why –OH is an o/p director.

(i) C₆H₅Cl + NaOH (623 K, 300 atm) → C₆H₅ONa → HCl → C₆H₅OH (Dow). (ii) C₆H₅SO₃Na + NaOH (fuse) → C₆H₅ONa + Na₂SO₃; acidify → phenol. (iii) C₆H₅N₂⁺Cl⁻ + H₂O (warm) → C₆H₅OH + N₂↑ + HCl. (iv) C₆H₅CH(CH₃)₂ + O₂ → cumene hydroperoxide → H⁺ → phenol + acetone (industrial).

(i) Reimer–Tiemann: phenol + CHCl₃ in aq. NaOH generates dichlorocarbene (:CCl₂) which attacks the ortho position; hydrolysis gives salicylaldehyde (2-hydroxybenzaldehyde). (ii) Kolbe: sodium phenoxide + CO₂ (400 K, 7 atm) then H⁺ → salicylic acid; the –OH activates the ortho C enough for the weakly electrophilic CO₂ to attack. (iii) Williamson: R–O⁻Na⁺ + R'–X (1°) → R–O–R' by SN2. The only practical general route to unsymmetrical ethers. (iv) Unsymmetrical (mixed) ether: R–O–R' where R ≠ R', e.g., CH₃OC₂H₅ (methoxyethane) or CH₃OC₆H₅ (anisole). Made most cleanly by Williamson synthesis.

Methoxymethane = CH₃–O–CH₃. Both groups primary → SN2: (1) Protonation: CH₃–O–CH₃ + H⁺ → CH₃–O⁺(H)–CH₃. (2) I⁻ attacks a methyl carbon from the back, expelling CH₃OH: I⁻ + CH₃–O⁺(H)–CH₃ → CH₃–I + CH₃OH. (3) Excess HI then reacts with the methanol formed: CH₃OH + HI → CH₃I + H₂O. Overall: CH₃OCH₃ + 2 HI → 2 CH₃I + H₂O.

(i) C₆H₅OCH₃ + CH₃Cl / anhyd. AlCl₃ → o- and p-methylanisole (p-major). (ii) C₆H₅OCH₃ + dil. HNO₃ → o- and p-nitroanisole. (iii) C₆H₅OCH₃ + Br₂ / CH₃COOH → p-bromoanisole (major) + o-bromoanisole. (iv) C₆H₅OCH₃ + CH₃COCl / anhyd. AlCl₃ → p-methoxyacetophenone (major) + o-isomer. All four: –OCH₃ activates the ring and directs ortho/para.

(i) Styrene + dilute H₂SO₄ (Markovnikov hydration) → C₆H₅CH(OH)CH₃. (ii) Cyclohexyl methyl bromide C₆H₁₁CH₂Br + aq. NaOH (SN2) → C₆H₁₁CH₂OH. Alternative: C₆H₁₁MgBr + HCHO → same alcohol. (iii) 1-bromobutane → Mg/ether → C₄H₉MgBr → + HCHO → + H₃O⁺ → CH₃(CH₂)₃CH₂OH (pentan-1-ol). Or directly: 1-bromopentane + aq. NaOH → pentan-1-ol (SN2).

(a) Phenol + aq. NaOH → sodium phenoxide + H₂O (irreversible and quantitative). (b) Phenol + Na metal → sodium phenoxide + ½ H₂↑. Phenol pKa ≈ 10; ethanol pKa ≈ 16. Phenol is about one million times more acidic than ethanol because its conjugate base (phenoxide) is stabilised by resonance into the aromatic ring (five resonance structures, three of which place negative charge on ortho/para carbons).

(i) Kolbe: ArONa + CO₂ (400 K, 7 atm) → ortho-hydroxyaryl carboxylic acid sodium salt → H⁺ → salicylic acid (from phenol). Industrial precursor to aspirin. (ii) Reimer–Tiemann: phenol + CHCl₃ + aq. NaOH → salicylaldehyde; mechanism via dichlorocarbene (:CCl₂), ortho attack, hydrolysis of the –CHCl₂ to –CHO. (iii) Williamson: R–O⁻Na⁺ + R'–X (where R'X is 1°) → R–O–R' + NaX. Example: CH₃ONa + C₂H₅Br → CH₃OC₂H₅ (methoxyethane). Mechanism = SN2.

(i) C₆H₅OH + 3 Br₂ (aq) → 2,4,6-tribromophenol (white ppt) + 3 HBr. (ii) C₆H₅ONa + CO₂ (400 K, 7 atm) → sodium salicylate → HCl → salicylic acid (2-hydroxybenzoic acid). [Kolbe] (iii) C₆H₅OH + dil. HNO₃ → o-nitrophenol + p-nitrophenol (separated by steam distillation; ortho is steam-volatile). (iv) C₆H₅OH + CHCl₃ + 3 NaOH → salicylaldehyde (o-HO–C₆H₄–CHO) + 3 NaCl + 2 H₂O. [Reimer–Tiemann] (v) C₆H₅OH + Na₂Cr₂O₇/H₂SO₄ → 1,4-benzoquinone (C₆H₄O₂) — bright yellow.