Class 12 Chemistry: Alcohols, Phenols & Ethers (Pages 3 to 6)

🌟 Ethers Classification & Vinylic Alcohols (Page 3 / Text Page 195)

Symmetrical / Simple Ethers

Identical Groups (R—O—R)

Both alkyl or aryl groups attached to oxygen are the same.
• Diethyl ether: C₂H₅—O—C₂H₅ (Ethoxyethane)
• Dimethyl ether: CH₃—O—CH₃ (Methoxymethane)

Unsymmetrical / Mixed Ethers

Different Groups (R—O—R′ / Ar—O—R)

The two alkyl/aryl groups attached to oxygen are different.
• Ethyl methyl ether: C₂H₅—O—CH₃
• Anisole (Methyl phenyl ether): C₆H₅—O—CH₃
• Phenetole (Ethyl phenyl ether): C₆H₅—O—C₂H₅

Vinylic Alcohols [C(sp²)—OH]

Direct Double Bond Attachment

–OH group is bonded directly to an sp²-hybridised vinylic carbon of a C=C double bond.
• Vinyl alcohol: CH₂=CH—OH (Ethenol)

🏷️ NCERT Nomenclature Master Tables (Pages 4 & 5 / Text Pages 196–197)

📋 Table 7.1: Alcohols (Common vs. IUPAC)

Chemical Formula	Common Name	IUPAC Name	Classification
CH₃—OH	Methyl alcohol	Methanol	Primary (1°)
CH₃—CH₂—CH₂—OH	n-Propyl alcohol	Propan-1-ol	Primary (1°)
CH₃—CH(OH)—CH₃	Isopropyl alcohol	Propan-2-ol	Secondary (2°)
(CH₃)₂CH—CH₂—OH	Isobutyl alcohol	2-Methylpropan-1-ol	Primary (1°)
(CH₃)₃C—OH	tert-Butyl alcohol	2-Methylpropan-2-ol	Tertiary (3°)
HO—CH₂—CH₂—OH	Ethylene glycol	Ethane-1,2-diol	Dihydric
CH₂OH—CHOH—CH₂OH	Glycerol	Propane-1,2,3-triol	Trihydric

📋 Phenols & Substituted Benzenediols

Structure	Common Name	IUPAC Name	Substitution
C₆H₄(OH)(CH₃) [1,2-]	o-Cresol	2-Methylphenol	ortho- (1,2-)
C₆H₄(OH)(CH₃) [1,3-]	m-Cresol	3-Methylphenol	meta- (1,3-)
C₆H₄(OH)(CH₃) [1,4-]	p-Cresol	4-Methylphenol	para- (1,4-)
C₆H₄(OH)₂ [1,2-]	Catechol	Benzene-1,2-diol	Dihydric Phenol
C₆H₄(OH)₂ [1,3-]	Resorcinol	Benzene-1,3-diol	Dihydric Phenol
C₆H₄(OH)₂ [1,4-]	Hydroquinone / Quinol	Benzene-1,4-diol	Dihydric Phenol

📋 Table 7.2: Ethers (Alkoxyalkanes)

Formula	Common Name	IUPAC Name	Parent Hydrocarbon
CH₃—O—CH₃	Dimethyl ether	Methoxymethane	Methane
C₂H₅—O—C₂H₅	Diethyl ether	Ethoxyethane	Ethane
CH₃—O—CH₂CH₂CH₃	Methyl n-propyl ether	1-Methoxypropane	Propane
C₆H₅—O—CH₃	Methyl phenyl ether (Anisole)	Methoxybenzene (Anisole)	Benzene
C₆H₅—O—CH₂CH₃	Ethyl phenyl ether (Phenetole)	Ethoxybenzene (Phenetole)	Benzene
(CH₃)₂CH—O—CH₃	Methyl isopropyl ether	2-Methoxypropane	Propane

🔬 3D Structure & Bond Geometry Comparison (Pages 6 & 7 / Text Pages 198–199)

Methanol (Alcohol)

CH₃—OH

• C—O—H Angle: 108.9° (< 109.5°)
• C—O Length: 142 pm
• O—H Length: 96 pm
• 💡 Reason: Repulsion between the two unshared lone electron pairs on Oxygen compresses the angle.

Phenol

C₆H₅—OH

• C—O—H Angle: 109°
• C—O Length: 136 pm (Shorter!)
• O—H Length: 96 pm
• 💡 Reason: (1) Partial double bond character via resonance with ring; (2) sp² carbon has higher s-character.

Methoxymethane (Ether)

CH₃—O—CH₃

• C—O—C Angle: 111.7° (> 109.5°)
• C—O Length: 141 pm
• 💡 Reason: Strong steric repulsion between the two bulky methyl (–CH₃) groups widens the angle!

⭐ Exam-Winning Insight: Why is the C—O bond in Phenol (136 pm) significantly shorter than in Methanol (142 pm)?
1. Conjugation: The unshared electron pair on oxygen conjugates with the benzene ring $\pi$-system, creating partial double bond character.
2. Hybridisation: In phenol, oxygen is bonded to an sp² carbon (33.3% s-character), which is more electronegative than the sp³ carbon (25% s-character) in methanol.

📝 25 Master Fill-in-the-Blanks Test (Pages 3 to 6)

Click the correct option pill for each question. Instant feedback, slot animations, and official NCERT explanations will be shown:

📊 Total Questions: 25

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