Alcohols — making and reactions
| English | Chinese | Pinyin |
|---|---|---|
| alcohol | 醇 | chún |
| hydroxyl | 羟基 | qiǎng jī |
| aldehyde | 醛 | quán |
| ketone | 酮 | tóng |
| ester | 酯 | zhǐ |
| dehydration | 脱水 | tuō shuǐ |
| distillation | 蒸馏 | zhēng liú |
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:
Alcohols are defined by the hydroxyl (–OH) group.
Alcohols contain the ______ functional group.
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?
NaOH(aq) substitutes the halogen for –OH; adding steam to an alkene or reducing a carbonyl also work.
Match each alcohol fact.
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:
Like water, alcohols react with sodium to give hydrogen — but more slowly.
Dehydrating an alcohol (hot Al₂O₃ or conc. acid) gives:
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