Alcohols, Phenols and Ethers Notes for NEET and JEE Main 2027 (PDF)

Alcohols, Phenols and Ethers is Unit 7 of NCERT Class 12 Chemistry Part II and falls under Organic Compounds Containing Oxygen in both the NEET UG and JEE Main syllabi. These notes cover classification, naming, preparation, acidity, the Lucas test, dehydration, oxidation, phenol reactions, Williamson synthesis and ether cleavage, with a free notes PDF.

Alcohols, Phenols and Ethers Notes for NEET and JEE Main

Section-wise key points from NCERT Unit 7, reaction tables, high-yield facts and common mistakes for NEET and JEE Main 2027 revision.

Alcohols, Phenols and Ethers at a Glance

Topics follow the NEET UG 2026 syllabus released by the National Medical Commission (NMC) in December 2025 and the JEE Main 2026 syllabus published by the National Testing Agency (NTA). Both stay the reference until the 2027 syllabi are out. Full lists: NEET syllabus and JEE Main syllabus.

How are alcohols, phenols and ethers classified?

An alcohol has –OH on a carbon of an aliphatic system (CH3OH), a phenol has –OH on a carbon of an aromatic ring (C6H5OH), and an ether has an alkoxy or aryloxy group (R–O or Ar–O) in place of a hydrogen.

Allylic and benzylic alcohols can themselves be primary, secondary or tertiary.

Nomenclature: Common and IUPAC Names

• Alcohols: replace the ‘e’ of the parent alkane with ‘ol’; number the longest chain from the end nearer the –OH group.
• Polyhydric alcohols keep the ‘e’ and add di, tri, etc. before ‘ol’: HO–CH2–CH2–OH is ethane-1,2-diol.
• Cyclic alcohols use the prefix cyclo, with the –OH carbon taken as C-1 (cyclohexanol).
• Phenol is both the common and the accepted IUPAC name; ortho, meta and para mean 1,2-, 1,3- and 1,4-disubstituted.
• Ethers: in IUPAC names the larger alkyl group is the parent hydrocarbon and the smaller one becomes the alkoxy prefix (CH3OC2H5 is methoxyethane; common name ethylmethyl ether).

Structure of the Functional Groups

• Alcohols: the C–O bond forms by overlap of sp3 orbitals of carbon and oxygen. The C–O–H angle is slightly less than the tetrahedral angle (109°28′) because of repulsion between the lone pairs on oxygen.
• Phenols: –OH is attached to an sp2 carbon. The C–O bond (136 pm) is slightly shorter than in methanol because of partial double bond character (conjugation of the oxygen lone pair with the ring) and the sp2 carbon.
• Ethers: the C–O–C angle is slightly greater than tetrahedral because the two bulky R groups repel each other; the C–O bond (141 pm) is almost the same as in alcohols.

How are alcohols and phenols prepared?

Alcohols come mainly from alkenes and carbonyl compounds; phenols come from benzene derivatives, and most of the world’s phenol is made from cumene.

Physical Properties of Alcohols, Phenols and Ethers

• Boiling points of alcohols and phenols rise with the number of carbon atoms (more van der Waals forces) and fall with branching (less surface area).
• Intermolecular hydrogen bonding gives alcohols and phenols higher boiling points than hydrocarbons, ethers, haloalkanes and haloarenes of comparable molecular mass. Ethanol boils far above propane; methoxymethane lies in between.
• Solubility in water comes from hydrogen bonding with water and falls as the alkyl or aryl (hydrophobic) part grows; several lower alcohols are miscible in all proportions.
• Ethers have a small net dipole moment but boil close to alkanes of similar mass: n-pentane 309.1 K, ethoxyethane 307.6 K, butan-1-ol 390 K.
• Ether solubility resembles that of alcohols of the same mass, because ether oxygen can hydrogen bond with water: ethoxyethane 7.5 g and butan-1-ol 9 g per 100 mL water; pentane is essentially immiscible.

Why are phenols more acidic than alcohols?

Phenoxide ion is stabilised by delocalisation of its negative charge over the ring, while in alkoxide ion the charge stays on oxygen; the sp2 carbon of phenol also increases the polarity of the O–H bond.

• Alcohols and phenols react with Na, K and Al to give alkoxides or phenoxides and H2; only phenols also react with aqueous NaOH. Both are Brönsted acids.
• Electron-releasing alkyl groups lower the acid strength of alcohols, so acidity falls from primary to secondary to tertiary.
• Alcohols are weaker acids than water; an alkoxide is a stronger base than hydroxide (sodium ethoxide is a stronger base than NaOH). Alcohols also act as Brönsted bases through the lone pairs on oxygen.
• Electron-withdrawing groups such as –NO2 raise phenol’s acidity, most at the ortho and para positions; electron-releasing groups lower it, so cresols are less acidic than phenol.
• The greater the pKa, the weaker the acid. Phenol (pKa 10.0) is about a million times more acidic than ethanol (pKa 15.9).

Reactions of Alcohols

Alcohols react as nucleophiles when the O–H bond breaks and, once protonated, as electrophiles when the C–O bond breaks. C–O cleavage happens only in alcohols; phenols show it only with zinc.

Mechanism of Dehydration of Ethanol

• Step 1: protonation of the alcohol.
• Step 2: loss of water to form a carbocation; this is the slowest, rate-determining step.
• Step 3: loss of a proton to form ethene. The acid used in step 1 is released, and ethene is removed as it forms to shift the equilibrium.

Methanol poisoning: in the body methanol is oxidised to methanal and then methanoic acid, which can cause blindness and death. Intravenous diluted ethanol is given so that the enzyme is swamped and the kidneys have time to excrete methanol.

Reactions of Phenols

The –OH group activates the ring and directs incoming electrophiles to the ortho and para positions through its resonance effect.

2,4,6-Trinitrophenol is a strong acid because its three –NO2 groups withdraw electrons and help release H+.

Methanol and Ethanol: Commercially Important Alcohols

• Invertase converts sugar to glucose and fructose (both C6H12O6); zymase from yeast ferments them to ethanol under anaerobic conditions, releasing CO2.
• Zymase is inhibited once alcohol exceeds 14 percent; air oxidises ethanol to ethanoic acid and spoils the taste.
• Denaturation: commercial alcohol is made unfit to drink by adding copper sulphate (colour) and pyridine (foul smell).

Ethers: Preparation and Reactions

Ethers are the least reactive of these functional groups. Diethyl ether was widely used as an inhalation anaesthetic but has been replaced because of its slow effect and unpleasant recovery.

Most-asked Facts for NEET and JEE Main: Alcohols, Phenols and Ethers

Revise these one-line facts from the NCERT chapter just before the exam.

• Hydroboration-oxidation gives the anti-Markovnikov alcohol; acid-catalysed hydration gives the Markovnikov alcohol.
• Grignard reagent with methanal gives a 1°, with other aldehydes a 2°, with ketones a 3° alcohol.
• Most phenol is made from cumene; acetone is the by-product.
• Lucas reagent is conc. HCl + ZnCl2; tertiary alcohols turn it turbid at once.
• Ease of dehydration: 3° > 2° > 1°; carbocation formation is the rate-determining step.
• PCC oxidises a primary alcohol only up to the aldehyde.
• Over heated Cu at 573 K, a tertiary alcohol is dehydrated to an alkene.
• Phenol pKa 10.0, ethanol 15.9; p-nitrophenol (7.1) is the most acidic of the nitrophenols in Table 7.3.
• o-Nitrophenol is steam volatile because of intramolecular hydrogen bonding.
• Bromine water with phenol gives a white precipitate of 2,4,6-tribromophenol.
• Kolbe’s reaction gives salicylic acid; Reimer-Tiemann reaction gives salicylaldehyde.
• Picric acid is 2,4,6-trinitrophenol; acetylation of salicylic acid gives aspirin.
• Ethanol with conc. H2SO4: ethene at 443 K, ethoxyethane at 413 K.
• Williamson synthesis needs a primary alkyl halide; a tertiary halide gives only an alkene.
• Anisole + HI gives phenol and methyl iodide, never iodobenzene.
• Zymase stops working above about 14 percent alcohol.

Common Mistakes to Avoid

Watch for these mix-ups when you answer questions on this chapter.

• Writing that alcohols are stronger acids than water. They are weaker; alkoxides are stronger bases than hydroxide.
• Ranking tertiary alcohols as the most acidic. Alkyl groups release electrons, so acidity falls from 1° to 3°.
• Thinking cresols are more acidic than phenol. The –CH3 group lowers acidity.
• Predicting iodobenzene from anisole and HI. The alkyl–oxygen bond breaks, giving phenol and CH3I.
• Using a tertiary alkyl halide in Williamson synthesis. Elimination wins and only an alkene forms; use the tertiary alkoxide with a primary halide instead.
• Expecting secondary or tertiary alcohols to give ethers on acid dehydration. They give alkenes.
• Saying p-nitrophenol is steam volatile. The ortho isomer is, because its hydrogen bonding is intramolecular.
• Adding FeBr3 for bromination of phenol or anisole. The –OH and –OCH3 groups activate the ring enough without a Lewis acid.
• Expecting tertiary alcohols to give ketones on oxidation. They resist normal oxidation.
• Confusing Kolbe’s reaction (CO2, gives an acid) with Reimer-Tiemann (CHCl3, gives an aldehyde).

Alcohols, Phenols and Ethers Notes PDF and Related Pages

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• Source text: NCERT Class 12 Chemistry Unit 7 (NCERT, Class 12 Chemistry Part II)

Chemistry Notes for NEET and JEE Main: All Chapters

• Some Basic Concepts of Chemistry
• Structure of Atom
• Chemical Kinetics
• Equilibrium
• Organic Chemistry: Some Basic Principles and Techniques
• Electrochemistry
• Amines
• Solutions
• Thermodynamics
• Coordination Compounds
• Haloalkanes and Haloarenes
• p-Block Elements
• Alcohols, Phenols and Ethers
• Hydrocarbons
• Aldehydes, Ketones and Carboxylic Acids

All chapters with key points and notes PDFs are on the Chemistry notes for NEET and JEE Main page.

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