Aldehydes and ketones
Introduced| English | Meaning |
|---|---|
| carbonyl compound/ˈkɑːbənaɪl ˈkɒmpaʊnd/ | A compound containing the C=O group: an aldehyde or a ketone. |
| 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. |
| reduction/rɪˈdʌkʃn/ | A chemical change involving a gain of electrons or a decrease in oxidation state. |
| hydroxynitrile/haɪˈdrɒksɪnaɪtraɪl/ | An organic compound containing both a hydroxyl group and a nitrile group. |
| nucleophilic addition/ˌnjuːklɪəˈfɪlɪk əˈdɪʃn/ | A reaction in which an electron-pair donor attacks an electron-deficient multiple bond, forming an addition product. |
The carbonyl compounds 羰基化合物
- These are carbonyl compounds — they contain the C=O group.
- In an aldehyde 醛 the C=O is on the end of the chain (–CHO).
- In a ketone 酮 it is in the middle, between two carbons.
Carbonyl compound lab
Sort carbonyl reactions by what they reveal.
The difference between an aldehyde and a ketone is that:
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Both have the carbonyl C=O; in an aldehyde it is terminal (–CHO), in a ketone it is between two carbons.
Aldehydes have the carbonyl group at the end of the carbon chain.
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Ketones have it in the middle.
Making them
- By oxidation of an alcohol (acidified $\text{K}_2\text{Cr}_2\text{O}_7$ or $\text{KMnO}_4$):
- a primary alcohol, with distillation, gives an aldehyde.
- a secondary alcohol gives a ketone.
In an aldehyde the C=O is on the end; in a ketone it is in the middle
Oxidising a secondary alcohol gives:
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Secondary alcohols oxidise to ketones; primary alcohols (with distillation) give aldehydes.
Match each carbonyl fact.
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Each item links the term to its correct meaning.
Reactions
- reduction 还原 ($\text{NaBH}_4$ or $\text{LiAlH}_4$) → back to an alcohol (aldehyde → primary; ketone → secondary).
- HCN (with KCN catalyst) adds H and CN across the C=O → a hydroxynitrile 羟基腈 (adds one carbon).
Tollens' reagent gives a bright silver mirror with an aldehyde.
Reducing a carbonyl compound (with NaBH₄) gives:
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Reduction turns a carbonyl back into an alcohol (aldehyde → primary, ketone → secondary).
Nucleophilic addition 亲核加成
The HCN reaction is nucleophilic addition:
- $\text{CN}^-$ (a nucleophile) attacks the slightly positive carbonyl carbon.
- the C=O double bond breaks, leaving a negative oxygen ($\text{O}^-$).
- the $\text{O}^-$ takes an $\text{H}^+$ to finish the hydroxynitrile.
Propanone (acetone), the simplest ketone, is the solvent in nail-polish remover.
In the nucleophilic addition of HCN, the first step is:
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The cyanide nucleophile attacks the δ+ carbon, breaking the C=O; the O⁻ then takes an H⁺.
You've got it
- carbonyl = C=O; aldehyde (end, –CHO) vs ketone (middle)
- made by oxidising an alcohol: primary + distillation → aldehyde; secondary → ketone
- reduction → alcohol; HCN → hydroxynitrile (+1 carbon)
- the HCN step is nucleophilic addition: $\text{CN}^-$ attacks the $\delta+$ carbon, C=O breaks, $\text{O}^-$ takes $\text{H}^+$