Organic structures and reaction pathways
הוצג| English | משמעות |
|---|---|
| functional group/ˈfʌŋkʃənl ɡruːp/ | קבוצה פונקציונלית |
| isomer/ˈaɪsəmə/ | איזומר |
What would explain this observation?
- Two compounds can have the same molecular formula but different structures. Their functional groups 官能团 help predict which reactions they undergo.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- A homologous series shares a functional group and general formula. Structural isomers 异构体 share a molecular formula but differ in atom connections. Alkenes contain a carbon-carbon double bond.
- functional group: An atom group determining characteristic reactions; isomer: A compound sharing a formula but differing in structure.
What happens to the carbon skeleton when bromine adds to ethene?
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Addition across C=C adds one bromine atom to each carbon; the two-carbon skeleton of ethene is untouched, giving 1,2-dibromoethane. No carbon-carbon bonds are broken, so no shortening or ring formation occurs.
Match each technical term to its precise meaning.
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Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Distinguish addition, substitution, oxidation and polymerization by tracing bonds before and after reaction. Conditions and reagents belong to the reaction arrow; they are not interchangeable labels.
- Draw displayed formulae with correct carbon and hydrogen valencies. For the specified alkene additions, keep the carbon skeleton and track the atoms added across C=C. Compare the supplied structure before and after reaction. GCSE 8462 does not require an advanced multistep synthesis route in this focus.
Which two habits make the investigation or model in this case more defensible?
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Stating the conditions and assumptions lets others repeat the work exactly, and recording the supporting evidence lets them check the conclusion. Hiding disagreeing results removes the evidence that could challenge a wrong conclusion, and one measurement can never establish a wider claim.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: ethene adds bromine across its double bond. The two-carbon skeleton stays intact and each carbon gains one bromine atom, giving 1,2-dibromoethane. One mole of ethene reacts with one mole of bromine in this addition reaction.
How many moles of bromine react completely with 0.15 mol ethene? Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
How many moles of bromine react completely with 0.15 mol ethene?
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The result is 0.15 mol. Known: 0.15 mol of ethene; the addition is C2H4 + Br2 -> C2H4Br2, a 1:1 mole ratio. Bromine amount = 1 x 0.15 = 0.15 mol. The balanced equation supplies the ratio.
Check the conclusion and its limits
- Bromine decolourization provides evidence of unsaturation in an appropriate test. It is not proof that an unknown sample is specifically ethene.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
Compounds with the same molecular formula always have identical properties. This claim is false: Same molecular formula is not same compound: isomers such as butane and 2-methylpropane share C4H10 but have different structures and different physical properties. Structure, not formula alone, sets properties.
Organic structures and reaction pathways: Distinguish addition, substitution, oxidation and polymerization by tracing bonds before and after reaction. Conditions and reagents belong to the reaction arrow; they are not interchangeable labels.
Compounds with the same molecular formula always have identical properties.
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Same molecular formula is not same compound: isomers such as butane and 2-methylpropane share C4H10 but have different structures and different physical properties. Structure, not formula alone, sets properties.
An atom group determining characteristic reactions: write the technical term.
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functional group means An atom group determining characteristic reactions.