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Alcohols, Phenols and Ethers

Acidity of alcohols and phenols, dehydration with its carbocation shifts, the named reactions of phenol, and the cleavage of ethers by HI.

Questions in the bank
102
q/paper in 2025–26
0.60
Calculation
13%
Notes pages
6

Strand: Reactions

When you’ll see it

An O–H or C–O–C compound is ranked by acidity, dehydrated or split by acid, or put through a named phenol reaction.

How this chapter is tested

Three habits carry most of the chapter. Rank acidity by how well the ion left behind spreads its negative charge. Follow the carbocation whenever an alcohol meets acid, and let it shift before the alkene forms. Decide which C–O bond HI breaks, remembering that the aryl–oxygen bond never does.

The rest is exact recall, where one swapped reagent costs the mark: which solvent gives which bromophenol, which nitrophenol steam distils, what CHCl₃ and CO₂ each put on the ring, and which phenol fails the phthalein test.

Numeric answers are small: active hydrogens counted by CH₃MgI, the mass gained on acetylation (42 per OH), the overall yield of a route (multiply the step yields), or how many compounds in a list pass a screen.

The sub-skills

The distinct skills inside the chapter, in the order to learn them.

  • Classes, preparation and boiling points

    Count carbons on the carbinol carbon, ring carbons included; acid hydration can shift, hydroboration cannot; NaBH₄ leaves acids alone; o-nitrophenol is chelated and steam volatile.

  • Acidity of alcohols and phenols

    Phenol (pKa 10.0) is far stronger than ethanol (15.9); p-nitro > o-nitro > m-nitro > phenol; m-OCH₃ strengthens, p-OCH₃ weakens; NaHCO₃ needs two or three o/p nitro groups.

  • Reactions of alcohols

    SOCl₂, PCl₅ or HX replace OH; Lucas: 3° clouds at once, 1° stays clear; PCC stops at the aldehyde; Cu at 573 K dehydrogenates 1° and 2°, dehydrates 3°.

  • Acid dehydration and shifts

    E1 through the carbocation; 1,2-hydride or methyl shifts and ring expansion first; then the most substituted, conjugated alkene.

  • Making phenol and its named reactions

    Dow, sulphonate fusion, diazonium + warm water, cumene hydroperoxide; Zn dust → benzene; Reimer–Tiemann (CHCl₃/NaOH) → salicylaldehyde; Kolbe (CO₂/NaOH) → salicylic acid.

  • Ring substitution of phenol

    Bromine water → 2,4,6-tribromophenol; Br₂ in CS₂ at low temperature → mainly p-bromophenol; dilute HNO₃ → o- and p-nitrophenol; picric acid via the disulphonic acid; phthalein test needs a free para H.

  • Ethers: Williamson and cleavage

    Alkoxide or phenoxide + CH₃ or 1° halide; HI attacks the smaller group, a 3° group leaves as the cation; ArOR + HI → ArOH + RI, never ArI.

Traps to expect

Distractor shapes this chapter reuses. The Traps page covers the ones that cut across chapters.

  • Ortho-nitrophenol as the strongest

    Its internal hydrogen bond holds the proton back, so p-nitrophenol is slightly stronger. m-Nitrophenol is the weakest of the three.

  • Reimer–Tiemann and Kolbe swapped

    CHCl₃ with NaOH puts CHO on the ring (salicylaldehyde, ortho major); CO₂ with sodium phenoxide puts COOH there (salicylic acid). The swap is the usual wrong pair in a match list.

  • The solvent in phenol bromination

    Water gives the tribromo product at once; CS₂ or CHCl₃ at low temperature gives mainly p-bromophenol. No FeBr₃ is needed in either case.

  • The wrong half of an ether

    With a methyl or primary partner iodide ends on the smaller group; with a tertiary partner it ends on the tertiary carbon. An aryl ether always gives the phenol and the alkyl iodide.

  • Benzyl alcohol treated as a phenol

    C₆H₅CH₂OH has its OH on a CH₂, so it gives no salt with NaOH and no FeCl₃ colour. Count it with the alcohols in a screen.

Learn it before you drill it

This chapter has full teaching notes — foundations, worked examples, self-checks and a mastery check for each page. Read the notes once, then drill page by page below.

Alcohols, Phenols and Ethers notes

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102 questions from the bank, across 6 subtopics.

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The 6 subtopics, in teaching order.

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