Name and display esters from four-carbon starting molecules
Trace alcohol-derived and acid-derived name parts, including esters larger than four carbons when each starting molecule meets the stated limit.
Exam scope and assessment notes
Extended only (Supplement) · Chemistry 0971, 2026–2028. Cambridge states that IGCSE 0971 has the same subject content as IGCSE 0620, with 9–1 grading. This StudyForA pathway maps the 2026–2028 syllabus only. This 9–1 graded qualification is available only in a limited number of administrative zones. Confirm that your centre can enter you for this code and exam series with Cambridge International. Cambridge has published a separate syllabus for 2029. StudyForA has not reconciled that version yet; this page supports exams in 2026, 2027 and 2028 only.
Before you begin
- Describe acid-catalysed esterification and identify C(=O)–O in a displayed structure.
- Name the unbranched one- to four-carbon acids and terminal-OH alcohols.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which name part comes from methanol?
What you will learn
- Name and draw the required unbranched esters from alcohols and acids each containing up to four carbons.
- Apply the carbon limit separately to the two starting molecules and check the ester linkage and water loss.
Each acid and each alcohol starting molecule contains at most four carbons. Their ester can contain up to eight. Open one acid group to compare its four terminal-attachment ester examples; two secondary-attachment comparisons follow separately.
Esters from methanoic acid · 4 terminal-attachment examples
Structural formula: HCOOCH₃.
Structural formula: HCOOCH₂CH₃.
Structural formula: HCOOCH₂CH₂CH₃.
Structural formula: HCOOCH₂CH₂CH₂CH₃.
Additional secondary-attachment comparisons · 2 structures
Structural formula: HCOOCH(CH₃)₂.
Additional comparison from a secondary attachment on an unbranched alcohol chain. Start with the terminal-attachment examples for the required unbranched-ester pattern.
Structural formula: HCOOCH(CH₃)CH₂CH₃.
Additional comparison from a secondary attachment on an unbranched alcohol chain. Start with the terminal-attachment examples for the required unbranched-ester pattern.
Esters from ethanoic acid · 4 terminal-attachment examples
Structural formula: CH₃COOCH₃.
Structural formula: CH₃COOCH₂CH₃.
Structural formula: CH₃COOCH₂CH₂CH₃.
Structural formula: CH₃COOCH₂CH₂CH₂CH₃.
Additional secondary-attachment comparisons · 2 structures
Structural formula: CH₃COOCH(CH₃)₂.
Additional comparison from a secondary attachment on an unbranched alcohol chain. Start with the terminal-attachment examples for the required unbranched-ester pattern.
Structural formula: CH₃COOCH(CH₃)CH₂CH₃.
Additional comparison from a secondary attachment on an unbranched alcohol chain. Start with the terminal-attachment examples for the required unbranched-ester pattern.
Esters from propanoic acid · 4 terminal-attachment examples
Structural formula: CH₃CH₂COOCH₃.
Structural formula: CH₃CH₂COOCH₂CH₃.
Structural formula: CH₃CH₂COOCH₂CH₂CH₃.
Structural formula: CH₃CH₂COOCH₂CH₂CH₂CH₃.
Additional secondary-attachment comparisons · 2 structures
Structural formula: CH₃CH₂COOCH(CH₃)₂.
Additional comparison from a secondary attachment on an unbranched alcohol chain. Start with the terminal-attachment examples for the required unbranched-ester pattern.
Structural formula: CH₃CH₂COOCH(CH₃)CH₂CH₃.
Additional comparison from a secondary attachment on an unbranched alcohol chain. Start with the terminal-attachment examples for the required unbranched-ester pattern.
Esters from butanoic acid · 4 terminal-attachment examples
Structural formula: CH₃CH₂CH₂COOCH₃.
Structural formula: CH₃CH₂CH₂COOCH₂CH₃.
Structural formula: CH₃CH₂CH₂COOCH₂CH₂CH₃.
Structural formula: CH₃CH₂CH₂COOCH₂CH₂CH₂CH₃.
Additional secondary-attachment comparisons · 2 structures
Structural formula: CH₃CH₂CH₂COOCH(CH₃)₂.
Additional comparison from a secondary attachment on an unbranched alcohol chain. Start with the terminal-attachment examples for the required unbranched-ester pattern.
Structural formula: CH₃CH₂CH₂COOCH(CH₃)CH₂CH₃.
Additional comparison from a secondary attachment on an unbranched alcohol chain. Start with the terminal-attachment examples for the required unbranched-ester pattern.
Choose each half of the name from the right source
The alcohol-derived alkyl name comes first: methanol gives methyl, ethanol ethyl, propan-1-ol propyl and butan-1-ol butyl in the terminal-attachment examples. The acid supplies methanoate, ethanoate, propanoate or butanoate from its corresponding acid. The four acid groups each show these four ester combinations with every atom and bond: sixteen terminal-attachment reference examples.
For ethyl propanoate, ethanol supplies –O–CH₂CH₃ and propanoic acid supplies CH₃CH₂C(=O)–, giving CH₃CH₂COOCH₂CH₃. For butyl methanoate, methanoic acid supplies HC(=O)– and butan-1-ol supplies –O–CH₂CH₂CH₂CH₃, giving HCOOCH₂CH₂CH₂CH₃. An ester's carbonyl carbon belongs to the acid-derived part; the bridging oxygen connects to the alcohol-derived carbon chain.
The four-carbon limit belongs to each starting molecule
The official requirement limits each unbranched alcohol and each acid starting molecule to at most four carbon atoms. Esterification loses water, so it loses no carbon: an ester from a four-carbon acid and a four-carbon alcohol contains eight carbons. Butyl butanoate CH₃CH₂CH₂COOCH₂CH₂CH₂CH₃ totals C₈H₁₆O₂, not a four-carbon molecular formula.
Draw every H, the carbonyl double bond and both single bonds of the bridging oxygen. An acid-plus-alcohol sum differs from the ester by H₂O; simply joining both full OH groups without water loss gives the wrong atoms or oxygen valence. The separate secondary-attachment comparison panels use propan-2-ol or butan-2-ol to connect with the earlier alcohol-position lesson; start with the sixteen terminal-attachment examples for the required unbranched-ester pattern, rather than counting those comparisons as extra required syllabus entries.
Pause and explain
Can an ester with eight carbons fit this required starting-molecule range?
Worked example
Name the ester from butanoic acid and butan-1-ol and check its total carbon count.
Show the worked solution
- The alcohol gives butyl and the acid gives butanoate.
- The structure is CH₃CH₂CH₂COOCH₂CH₂CH₂CH₃.
- Four carbons from each reactant are retained: C₈H₁₆O₂ after loss of H₂O from C₈H₁₈O₃.
Answer Butyl butanoate, CH₃CH₂CH₂COOCH₂CH₂CH₂CH₃, C₈H₁₆O₂; eight carbons satisfy the separate four-carbon starting-molecule limits.
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Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Name and draw the ester from methanoic acid and ethanol, then count its atoms.
Give me a hint
Use HCOO for the acid-derived side and CH₂CH₃ for the alcohol-derived side.
Compare my reasoning
- Ethanol supplies ethyl and methanoic acid supplies methanoate.
- The structure is HCOOCH₂CH₃, with HC(=O)–O–CH₂–CH₃ connectivity.
- Its atom totals are C₃H₆O₂; draw each H and preserve both bonds at the bridging O.
Ethyl methanoate HCOOCH₂CH₃, C₃H₆O₂, displayed with the carbonyl and bridging oxygen bonds explicit.
Look for these in your work
- Both name parts come from the stated partners.
- Every atom and bond matches the total.
Give the starting molecules, structural formula and molecular total for propyl ethanoate.
Give me a hint
Propyl uses the terminal-OH three-carbon alcohol in this required pattern.
Compare my reasoning
- Start with propan-1-ol and ethanoic acid, using an acid catalyst.
- The product structure is CH₃COOCH₂CH₂CH₃.
- Two acid carbons plus three alcohol carbons give C₅H₁₀O₂, with water as the other product.
Propan-1-ol + ethanoic acid, acid catalyst; propyl ethanoate CH₃COOCH₂CH₂CH₃ (C₅H₁₀O₂) plus water.
Look for these in your work
- The name is traced to both correct reactants.
- Structure, carbon total and water coproduct agree.
A student rejects butyl butanoate as outside the syllabus because its eight carbons exceed four. Explain the actual limit and check water loss from the starting molecular totals.
Give me a hint
Apply the limit to each reactant independently before adding their atoms.
Compare my reasoning
- Butanoic acid C₄H₈O₂ and butan-1-ol C₄H₁₀O each meet the four-carbon limit.
- Their sum is C₈H₁₈O₃; removing H₂O gives ester C₈H₁₆O₂.
- The eight carbons are retained from the two permitted partners, so the rejection uses the wrong scope rule.
Each reactant has four carbons; C₄H₈O₂+C₄H₁₀O minus H₂O gives butyl butanoate C₈H₁₆O₂, within the stated starting-molecule range.
Look for these in your work
- The carbon limit is applied separately.
- Water loss and the final atom totals are correct.
Common mistakes
- Reversing the alcohol and acid name parts.
- Limiting the combined ester to four carbons when each reactant is allowed four.
- Omitting the acid's carbonyl carbon from the total.
- Keeping both full OH groups in the ester and ignoring water loss.
What can you explain now?
Which reactants produce ethyl propanoate under esterification conditions?
Compare with the explanation
Ethanol and propanoic acid, with an acid catalyst.
Ethyl identifies the alcohol-derived part; propanoate identifies the acid-derived part.
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Make it stick
Choose an acid and alcohol from the allowed terminal-attachment range, predict the name and complete displayed structure, then open that acid group's reference to check the linkage and atoms.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.