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Alcohols, Phenols & Ethers revision notes

Every idea in the Alcohols, Phenols & Ethers chapter for JEE Main, with the usual mistakes and the fast methods. Topic 1 is open to everyone; sign in free to read all 19 and download the PDF.

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Alcohols: structure, properties and preparation

Structure and classification
2× asked, last 2026
C−O (pm): CHX3OH 142>CHX3OCHX3 141>CX6HX5OH 136∠C−O−H (CHX3OH) 108.9∘;∠C−O−C (CHX3OCHX3) 111.7∘\begin{gathered}\ce{C-O}\ (\text{pm}):\ \ce{CH3OH}\ 142 > \ce{CH3OCH3}\ 141 > \ce{C6H5OH}\ 136\\ \angle\ce{C-O-H}\ (\ce{CH3OH})\ 108.9^\circ;\qquad \angle\ce{C-O-C}\ (\ce{CH3OCH3})\ 111.7^\circ\end{gathered}
1°/2°/3° = carbons on the carbinol C, per OH. Phenol C–O is short (sp2sp^2 C, partial double bond); a ring donor lengthens it.
C 1° O H
ethanol
1°: 1 C on the carbinol C
C 2° O H
propan-2-ol
2°: 2 C on the carbinol C
C 3° O H
2-methylpropan-2-ol
3°: 3 C on the carbinol C
C 1° O H
2,2-dimethylpropan-1-ol
1°: 1 C on the carbinol C
108.9°CH₃HO····142 pm111.7°CH₃CH₃O····141 pm141 pm136 pmOHphenol: sp² C, partial C=Olone pairs squeeze it:below 109.5°bulky CH₃ groups open it:above 109.5°
All bonds drawn to one scale from the sheet’s C–O lengths and angles (ring C–C 139 pm and O–H 96 pm standard)
  • Ether O is sp3sp^3 with two lone pairs (bent, polar). C–O–C (111.7°) exceeds 109.5° as the two bulky R groups repel; C–O–H in alcohols (108.9°) is below 109.5° due to lone-pair repulsion.
Boiling point and solubility
2× asked, last 2025
bp (similar mass): alcohol>aldehyde/ketone>ether≈alkane\text{bp (similar mass): alcohol} > \text{aldehyde/ketone} > \text{ether} \approx \text{alkane}
Alcohols H-bond to each other; branching lowers bp. Ethers only accept H-bonds: EtX2O\ce{Et2O} 7.5 g vs butan-1-ol 9 g per 100 mL.
309alkane337ether375ketone392alcoholb.p. (K)
C5: pentane (M 72, Alkanes sheet), ethyl propyl ether (88), pentan-3-one (86), pentan-2-ol (88), standard b.p.; the order is the sheet’s
7.5Et₂O9butan-1-olg / 100 mL water
Both C₄H₁₀O (sheet)
  • Not 'ketone ≈ ether'. The C=O dipole is far larger, so dipole–dipole forces raise the bp. For C5: pentane < ethyl propyl ether < pentan-3-one < pentan-2-ol.
Hydration and reduction routes
2× asked, last 2026
CHX3CH=CHX2→HX2O/HX+CHX3CH(OH)CHX3 (Markovnikov);→(ii) HX2OX2/OHX−(i) BX2HX6CHX3CHX2CHX2OH (anti-M.)RCHO→NaBHX4RCHX2OH,RX2CO→LiAlHX4RX2CHOH,RCOOH→(ii) HX2O(i) LiAlHX4RCHX2OH\begin{gathered}\ce{CH3CH=CH2 ->[H2O/H+] CH3CH(OH)CH3}\ (\text{Markovnikov});\quad \ce{->[(i) B2H6][(ii) H2O2/OH-] CH3CH2CH2OH}\ (\text{anti-M.})\\ \ce{RCHO ->[NaBH4] RCH2OH},\quad \ce{R2CO ->[LiAlH4] R2CHOH},\quad \ce{RCOOH ->[(i) LiAlH4][(ii) H2O] RCH2OH}\end{gathered}
Acid route: carbocation, may rearrange; hydroboration: none. NaBHX4\ce{NaBH4} spares COOH, esters, C=C; LiAlHX4\ce{LiAlH4} reduces acids.
propene
HX2O/HX+\ce{H2O/H+}
 
O H
propan-2-ol
(Markovnikov)
propene
(i) BX2HX6\ce{B2H6}
(ii) HX2OX2/OHX−\ce{H2O2/OH-}
O H
propan-1-ol
(anti-Markovnikov)
3,3-dimethylbut-1-ene
HX2O/HX+\ce{H2O/H+}
via 2° C⁺, CH₃ shift → 3° C⁺
O H
2,3-dimethylbutan-2-ol
O O O H
4-formylbenzoic acid
NaBHX4\ce{NaBH4}
 
O H O O H
only CHO reduced
O O O H
4-formylbenzoic acid
LiAlHX4\ce{LiAlH4}
 
O H O H
CHO and COOH reduced
  • Not the plain Markovnikov alcohol next to a quaternary C. A methyl shift gives the 3° cation: 3,3-dimethylbut-1-ene + HX2O/HX+\ce{H2O/H+} gives 2,3-dimethylbutan-2-ol.
  • Not alcohols from ozonolysis or from alkyne hydration (HgX2+/HX+\ce{Hg^{2+}/H+}). Both stop at carbonyl compounds; only a following NaBHX4\ce{NaBH4}/LiAlHX4\ce{LiAlH4} step gives the alcohol.
Grignard route to 1°, 2°, 3° alcohols
4× asked, last 2026
HCHO→1∘,RCHO→2∘,RX2CO→3∘RX′COORX′′+2 RMgX→RX′RX2COH (3∘, RX′≠H);HCOORX′′+2 RMgX→RX2CHOH (2∘)\begin{gathered}\ce{HCHO} \to 1^\circ,\quad \ce{RCHO} \to 2^\circ,\quad \ce{R2CO} \to 3^\circ\\ \ce{R'COOR'' + 2RMgX} \to \ce{R'R2COH}\ (3^\circ,\ \ce{R'} \ne \ce{H});\qquad \ce{HCOOR'' + 2RMgX} \to \ce{R2CHOH}\ (2^\circ)\end{gathered}
Dry ether; HX3OX+\ce{H3O+} hydrolyses the adduct. Ester: the carbonyl formed first reacts faster, so 2 RMgX add (two identical R).
CarbonylNameGrignard (then H₃O⁺)Alcohol formedClass
O
HCHO1 CH₃MgBr
O H
1°
O
CH₃CHO1 CH₃MgBr
O H
2°
O
CH₃COCH₃1 CH₃MgBr
O H
3°
O O
CH₃COOC₂H₅2 CH₃MgBr
O H
3°
O O
HCOOC₂H₅2 CH₃MgBr
O H
2°
Each product is built by adding CH₃ to the C=O carbon; an ester first loses OC₂H₅ (as C₂H₅OH) and the ketone formed takes a second CH₃.
Commercial methanol and ethanol
3× asked, last 2026
CO+2 HX2→ZnO−CrX2OX3CHX3OH,CX6HX12OX6→zymase2 CX2HX5OH+2 COX2\ce{CO + 2H2 ->[ZnO-Cr2O3] CH3OH},\qquad \ce{C6H12O6 ->[zymase] 2C2H5OH + 2CO2}
Methanol: 573–673 K, 200–300 atm. Invertase splits sucrose first; fermentation runs without air (air turns ethanol to acid).
glucose 180 g1 mol in2 C₂H₅OH 92 g2 CO₂ 88 goutat most 51% of the sugar’s mass ends up as ethanol
Fermentation by mass, from the balanced equation (M from the formulas)
  • Controlled alkane oxidation: CHX4+OX2\ce{CH4 + O2} over Cu (523 K, 100 atm) gives CHX3OH\ce{CH3OH}, over MoX2OX3\ce{Mo2O3} HCHO; (CHX3COO)X2Mn\ce{(CH3COO)2Mn} turns ethane into CHX3COOH\ce{CH3COOH}; KMnOX4\ce{KMnO4} turns (CHX3)X3CH\ce{(CH3)3CH} into (CHX3)X3COH\ce{(CH3)3COH}.

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14 more concepts in 4 topics

Reactions of alcohols, Phenols: preparation and acidity, Reactions of phenol and Ethers. Read the first part free. Sign in free with Google to read the rest and download the PDF.

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Reactions of alcohols

  • Acidity and reaction with Na2×
  • Esterification and acetylation2×
  • HX, PCl₅, SOCl₂ and the Lucas test2×
  • Dehydration: mechanism and conditions4×
  • Oxidation and Cu at 573 K4×
  • Also remember1

Phenols: preparation and acidity

  • Preparation of phenol2×
  • Acidity of phenol4×
  • Substituent effects on phenol acidity3×

Reactions of phenol

  • Bromination: the solvent decides3×
  • Nitration and sulphonation3×
  • Kolbe and Reimer–Tiemann reactions9×
  • Zn dust, oxidation and tests7×

Ethers

  • Williamson synthesis3×
  • Cleavage by HI5×
  • Also remember1

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