Alcohols — making and reactions
Introduced| English | Meaning |
|---|---|
| alcohol/ˈælkəhɒl/ | An organic compound with a hydroxyl group bonded to a saturated carbon atom. |
| hydroxyl/haɪˈdrɒksɪl/ | The functional group consisting of an oxygen atom bonded to a hydrogen atom, written OH. |
| aldehyde/ˈældɪhaɪd/ | An organic compound containing a carbonyl group bonded to at least one hydrogen atom. |
| ketone/ˈketəʊn/ | An organic compound with a carbonyl carbon bonded to two carbon groups. |
| ester/ˈestə/ | An organic compound containing a carbonyl group bonded to an oxygen atom that is bonded to another carbon group. |
| dehydration/ˌdiːhaɪˈdreɪʃn/ | The removal or loss of water from a substance or organism. |
| distillation/dɪstɪˈleɪʃn/ | Separating substances by vaporising and condensing them, using differences in volatility or boiling point. |
The versatile -OH group
- An alcohol 醇 has the –OH (hydroxyl 羟基) functional group.
- It is a versatile, central organic compound.
- It can be made several ways and reacts in many.
Alcohol reaction map
Choose what happens to alcohols under different reagents.
The functional group of an alcohol is:
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Alcohols are defined by the hydroxyl (–OH) group.
Alcohols contain the ______ functional group.
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Written –OH.
Making alcohols
- steam + an alkene ($\text{H}_3\text{PO}_4$ catalyst) — electrophilic addition.
- halogenoalkane + NaOH(aq), heat — nucleophilic substitution.
- reduction of an aldehyde 醛/ketone 酮 ($\text{NaBH}_4$ or $\text{LiAlH}_4$).
- hydrolysis of an ester 酯 (dilute acid or alkali, heat).
Acidified dichromate turns orange to green with a primary or secondary alcohol
An alcohol can burn, dehydrate, esterify or be oxidised
Which reaction makes an alcohol?
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NaOH(aq) substitutes the halogen for –OH; adding steam to an alkene or reducing a carbonyl also work.
Match each alcohol fact.
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Each item links the term to its correct meaning.
Reactions of alcohols
- combustion → carbon dioxide + water.
- with sodium → hydrogen + a sodium alkoxide (like water, but slower).
- substitution to a halogenoalkane ($\text{HX}$, $\text{PCl}_5$, $\text{SOCl}_2$).
- dehydration 脱水 → an alkene (hot $\text{Al}_2\text{O}_3$ or conc. acid).
- ester formation with a carboxylic acid (conc. $\text{H}_2\text{SO}_4$ catalyst).
Fractional distillation 蒸馏 separates ethanol from a fermented mixture.
An alcohol reacting with sodium metal produces:
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Like water, alcohols react with sodium to give hydrogen — but more slowly.
Dehydrating an alcohol (hot Al₂O₃ or conc. acid) gives:
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Dehydration removes water from the alcohol to form an alkene (the reverse of steam addition).
Three classes of alcohol
- Primary, secondary and tertiary alcohols differ by how many carbons attach to the C–OH carbon.
- The class decides what oxidation gives (aldehyde/acid, ketone, or no reaction).
Primary, secondary and tertiary alcohols differ by the number of carbons on the C–OH carbon
You've got it
- alcohols have the –OH group
- made from: steam + alkene, halogenoalkane + NaOH(aq), reduction of aldehyde/ketone, ester hydrolysis
- react by combustion, with sodium (→ H₂), dehydration (→ alkene), and ester formation