Chemistry (AS Level)·Hydroxyl compounds · NSSCAS 4.4.1
Alcohols
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Meet the alcohols — the family built around the hydroxyl group, O–H. You'll learn to read their displayed, condensed and skeletal formulae, name them up to six carbons like propan-1-ol and propan-2-ol, and sort them into primary, secondary and tertiary. Then, using ethanol as the model, you'll master a whole toolkit of reactions: combustion, substitution to halogenoalkanes, reaction with sodium, oxidation with the orange-to-green dichromate, dehydration to alkenes and esterification. Finally you'll meet two distinguishing tests and see why alcohols make such useful solvents.
What you'll learn in this lesson
By the end you should be able to (NSSCAS Chemistry (AS Level) 4.4.1):
- Interpret and use general, structural (condensed/semi-structural and displayed) and skeletal formulae of alcohols (primary, secondary and tertiary)
- Name alcohols up to six carbons, e.g. propan-1-ol, propan-2-ol
- Deduce the molecular formula of an alcohol (including 1°, 2°, 3°) from a given structure
- Recall the chemistry of ethanol: combustion; substitution to halogenoalkanes (HBr, PCl₅/PCl₃, SOCl₂); reaction with sodium to give sodium ethoxide and hydrogen; oxidation to carbonyl compounds and carboxylic acids; dehydration to alkenes; esterification to form esters
- Classify hydroxy compounds into primary, secondary and tertiary alcohols and show that tertiary alcohols are not oxidised
- Suggest characteristic distinguishing reactions, e.g. mild oxidation with acidified dichromate (orange → green)
- Deduce the presence of a CH₃CH(OH)– group from its reaction with alkaline aqueous iodine to form tri-iodomethane (iodoform, yellow precipitate)
- Explain why alcohols are used as solvents, including in cosmetics and to remove sulfur compounds from coal
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