Flashcards · 9701 · AS Topic 16

Hydroxy compounds (AS Level) flashcards

7 cards on AS Topic 16. Pick a subtopic or study them all.

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Oxidation products of primary, secondary and tertiary alcohols: Primary: aldehyde, then carboxylic acid. Secondary: ketone (no further). Tertiary: not oxidised.
Primary alcohol with acidified K₂Cr₂O₇: how do you get the aldehyde rather than the acid?: Distil as it forms, so the aldehyde leaves before it is oxidised further. Heating under reflux with excess oxidant gives the carboxylic acid.
Colour change when acidified dichromate(VI) oxidises an alcohol: Orange → green (Cr₂O₇²⁻ → Cr³⁺). A tertiary alcohol leaves it orange.
Dehydration of an alcohol: Heat with concentrated H₂SO₄ or H₃PO₄ (about 170 °C): elimination of water gives an alkene.
Alcohols with sodium, and with PCl₅: Na: sodium alkoxide + hydrogen (effervescence). PCl₅: chloroalkane + HCl + POCl₃ (misty fumes of HCl).
Why are alcohols weaker acids than water?: The electron-donating alkyl group makes the O–H hydrogen less easily released and makes the alkoxide ion (RO⁻) less stable than OH⁻.
Iodoform test: which alcohols give a positive result?: Those containing CH₃CH(OH)–, e.g. ethanol and propan-2-ol. Warm with alkaline I₂(aq): yellow precipitate of CHI₃.