Higher Tier: two-ended monomers form a polyester
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| condensation polymerisation/kɒndenˈseɪʃn ˌpɒlɪməraɪˈzeɪʃn/ | 缩合聚合 | suō hé jù hé |
| polyester/ˌpɒlɪˈestə/ | 聚酯 | jù zhǐ |
What would explain this observation?
- Higher Tier: An alcohol molecule with two OH groups can join at both ends. Together with a molecule bearing two COOH groups, it can form a chain rather than stopping after a single ester link.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- Condensation polymerisation 缩合聚合 joins monomers with two functional groups, usually losing small molecules such as water. The acquired specification example pairs ethanediol HO–CH₂–CH₂–OH with hexanedioic acid HOOC–(CH₂)₄–COOH. Each monomer has two of the same functional group. Alcohol and carboxylic-acid ends react to form ester links C(=O)–O, leaving functional groups available to extend the chain. The resulting polyester 聚酯 contains residues of both monomer types.
- condensation polymerisation: Joining multifunctional monomers while forming small-molecule by-products in the stated reaction; polyester: A polymer containing repeated ester links in its backbone.
Why can the stated diol and diacid continue forming a chain?
Read the ideal repeating interior as –O–CH₂–CH₂–O–C(=O)–(CH₂)₄–C(=O)–. The CH₂–CH₂ segment came from the diol, and the four-CH₂ segment and carbonyl carbons came from the diacid. At each joining event, H from an alcohol OH and OH from an acid COOH make water. The remaining oxygen links the carbonyl carbon to the diol segment. Unlike addition polymerisation, the repeat therefore does not retain every atom of the original monomer pair.
Match each technical term to its precise meaning.
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Read the ideal repeating interior as –O–CH₂–CH₂–O–C(=O)–(CH₂)₄–C(=O)–. The CH₂–CH₂ segment came from the diol, and the four-CH₂ segment and carbonyl carbons came from the diacid. At each joining event, H from an alcohol OH and OH from an acid COOH make water. The remaining oxygen links the carbonyl carbon to the diol segment. Unlike addition polymerisation, the repeat therefore does not retain every atom of the original monomer pair.
- Build a paper or model-kit chain from two-ended diol and diacid cards. Join only compatible ends, mark each ester link and place one water card beside each actual joining event. A single OH/COOH pair cannot extend indefinitely at both ends. Compare the repeat with both starting molecules and explain which functional groups enabled growth. This modelling task is not permission to perform an unapproved polymer synthesis in the laboratory.
Which two habits make the investigation or model in this case more defensible?
Build a paper or model-kit chain from two-ended diol and diacid cards. Join only compatible ends, mark each ester link and place one water card beside each actual joining event. A single OH/COOH pair cannot extend indefinitely at both ends. Compare the repeat with both starting molecules and explain which functional groups enabled growth. This modelling task is not permission to perform an unapproved polymer synthesis in the laboratory.
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: a finite, unbranched chain is built from three diol and three diacid molecules, with no ring or extra cross-links. Six molecules require five joining links, so five H₂O molecules are formed. The schematic long-chain specification equation uses the ideal repeating-unit convention; exact finite-chain water counts depend on remaining end groups. Counting actual links avoids treating that convention as a measured end-group formula.
A finite open chain joins eight monomer molecules through seven condensation links, losing one H₂O per link. Count water molecules. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
A finite open chain joins eight monomer molecules through seven condensation links, losing one H₂O per link. Count water molecules.
The result is 7 molecules. Known: a finite, unbranched chain is built from three diol and three diacid molecules, with no ring or extra cross-links. Six molecules require five joining links, so five H₂O molecules are formed. The schematic long-chain specification equation uses the ideal repeating-unit convention; exact finite-chain water counts depend on remaining end groups. Counting actual links avoids treating that convention as a measured end-group formula.
Check the conclusion and its limits
- A polyester contains many ester links; the name does not mean every polymer is an ester. Condensation can form other link types, and the lost small molecule need not always be water. Retain the carbonyl double bond in C(=O)–O. This whole objective is Higher Tier Chemistry-only content; it must not make common-tier addition polymerisation Higher-only.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
Condensation polymerisation must retain every atom of the starting monomers in the polymer. This claim is false: A polyester contains many ester links; the name does not mean every polymer is an ester. Condensation can form other link types, and the lost small molecule need not always be water. Retain the carbonyl double bond in C(=O)–O. This whole objective is Higher Tier Chemistry-only content; it must not make common-tier addition polymerisation Higher-only.
Higher Tier: two-ended monomers form a polyester: Read the ideal repeating interior as –O–CH₂–CH₂–O–C(=O)–(CH₂)₄–C(=O)–. The CH₂–CH₂ segment came from the diol, and the four-CH₂ segment and carbonyl carbons came from the diacid. At each joining event, H from an alcohol OH and OH from an acid COOH make water. The remaining oxygen links the carbonyl carbon to the diol segment. Unlike addition polymerisation, the repeat therefore does not retain every atom of the original monomer pair.
Condensation polymerisation must retain every atom of the starting monomers in the polymer.
A polyester contains many ester links; the name does not mean every polymer is an ester. Condensation can form other link types, and the lost small molecule need not always be water. Retain the carbonyl double bond in C(=O)–O. This whole objective is Higher Tier Chemistry-only content; it must not make common-tier addition polymerisation Higher-only.
Joining multifunctional monomers while forming small-molecule by-products in the stated reaction: write the technical term.
condensation polymerisation means Joining multifunctional monomers while forming small-molecule by-products in the stated reaction.