--- title: "Isomers Worksheet with Answers (Free PDF) | MolDraw" url: https://www.moldraw.com/educational-materials/isomers-worksheet/ description: "Isomers worksheet with answers: draw all structural isomers of C5H12, C4H8, C4H10O and C3H6O, then tackle cis/trans and optical isomer questions. Free PDF." lang: en publisher: Scidart Academy generated: 2026-10-28 --- [MolDraw](https://www.moldraw.com/) › [Educational materials](https://www.moldraw.com/educational-materials/) › Structural Isomers & Stereoisomers Worksheet # Structural Isomers & Stereoisomers Worksheet Organic chemistryGrades 11–12 · A-level / IB · AP Chemistry · CBSE/JEE · Intro college organic10 items · answer key included This isomers worksheet asks students to draw every structural isomer of a molecular formula and then think about stereoisomers. Part A covers the classic exam formulas: the 3 isomers of C5H12, the 6 isomers of C4H8 (including cyclic and cis/trans forms), the 7 alcohols and ethers of C4H10O and the carbonyl, alcohol, ether and ring isomers of C3H6O. Part B practises cis/trans (E/Z) and optical isomerism, including meso compounds. The answer key shows every structure with its IUPAC name, and each count was checked by computer enumeration, so this structural isomers worksheet with answers is reliable for homework, revision or a printable PDF test. ## Customise Sheet title Subtitle School / teacher Student lines Name Class Date Answers None Answer key page Inline Text size S M L Structure size 100% Questions Part A — Draw all the structural isomers Draw and name all the structural isomers of C5H12. Draw and name all the isomers of C4H8, including cyclic compounds and… Draw and name all the structural isomers of C4H10O. Classify each as… C3H6O: (a) draw and name the two carbonyl compounds; (b) draw and nam… Draw and name all the structural isomers of C3H8O. Which one is an et… Part B — Stereoisomers But-2-ene shows cis/trans (E/Z) isomerism but but-1-ene does not. Dra… Mark the chiral centre in butan-2-ol and draw its two enantiomers as… 2,3-Dibromobutane has two stereocentres. How many stereoisomers does… Draw the stereoisomers of 1,2-dimethylcyclopropane. Which ones are ch… Which of these show cis/trans isomerism: (a) pent-1-ene, (b) pent-2-e… Live A4 preview. “Download PDF” opens the print dialog: choose **Save as PDF**. Click a structure to open it in MolDraw. ## Structural Isomers & Stereoisomers Worksheet Name Class Date ## Part A — Draw all the structural isomers Draw and name every structural (constitutional) isomer of each formula. Then note any that also show stereoisomerism. 1. Draw and name all the structural isomers of **C5H12**. **3 isomers:** pentane; 2-methylbutane; 2,2-dimethylpropane.![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-d8bfc2ccb9.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-b5ee965b45.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-08eb63888c.svg) 2. Draw and name all the isomers of **C4H8**, including cyclic compounds and cis/trans isomers. **6 isomers** (5 structural + 1 extra stereoisomer): but-1-ene; (*Z*)-but-2-ene (cis); (*E*)-but-2-ene (trans); 2-methylpropene; cyclobutane; methylcyclopropane.![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-b24334aa53.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-0e4d74cd93.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-ce8f5b20a3.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-62b5354df5.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-18004bfa31.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-e4a73e19e0.svg) 3. Draw and name all the structural isomers of **C4H10O**. Classify each as an alcohol (primary, secondary or tertiary) or an ether. **7 isomers.** Alcohols: butan-1-ol (1°); butan-2-ol (2°, chiral — exists as *R* and *S*); 2-methylpropan-1-ol (1°); 2-methylpropan-2-ol (3°). Ethers: 1-methoxypropane; 2-methoxypropane; ethoxyethane (diethyl ether).![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-069ca54449.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-7908c955ad.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-4560bdf298.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-8ec5351bef.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-ab8f118ba8.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-516c2cb206.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-0df3bfd023.svg) 4. **C3H6O**: (a) draw and name the two carbonyl compounds; (b) draw and name as many other structural isomers as you can (alcohols, ethers and rings). (a) propanal (aldehyde) and propanone (acetone, ketone). (b) prop-2-en-1-ol (allyl alcohol); methoxyethene (methyl vinyl ether); cyclopropanol; oxetane; 2-methyloxirane (propylene oxide, chiral); plus the unstable enols prop-1-en-1-ol (*E*/*Z*) and prop-1-en-2-ol. **9 structural isomers in total** (7 if enols are excluded).![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-72e102d3b3.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-a2fe2176ee.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-adeb0f5b19.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-f47c23de60.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-98ba397abe.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-a6dd04aa7d.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-8556413b2b.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-5721bf2466.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-67ad3f0b3b.svg) 5. Draw and name all the structural isomers of **C3H8O**. Which one is an ether? **3 isomers:** propan-1-ol; propan-2-ol; methoxyethane (ethyl methyl ether — the ether). The two alcohols are position isomers; the ether is a functional group isomer of them.![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-59d8b57bbf.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-35326b933c.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-6ec047cbd2.svg) ## Part B — Stereoisomers Answer each question. Use wedges and dashes where you need to show 3-D arrangement. 6. But-2-ene shows cis/trans (*E*/*Z*) isomerism but but-1-ene does not. Draw both isomers of but-2-ene and explain the difference. ![Structure for the question](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-dd69b3e4bf.svg) Restricted rotation about C=C plus two *different* groups on *each* alkene carbon is needed. In but-2-ene each carbon carries H and CH3, giving (*Z*)-but-2-ene (cis, CH3 groups same side) and (*E*)-but-2-ene (trans). In but-1-ene, C1 carries two H atoms, so no geometric isomers exist.![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-0e4d74cd93.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-ce8f5b20a3.svg) 7. Mark the chiral centre in butan-2-ol and draw its two enantiomers as wedge/dash structures. ![Structure for the question](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-7908c955ad.svg) C2 (bonded to H, OH, CH3 and CH2CH3) is the chiral centre. The two non-superimposable mirror images are (*R*)-butan-2-ol and (*S*)-butan-2-ol.![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-d14035a13a.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-37ce944213.svg) 8. 2,3-Dibromobutane has two stereocentres. How many stereoisomers does it have? Explain why it is fewer than 22 = 4. ![Structure for the question](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-8eeffb0790.svg) **3 stereoisomers:** (2*R*,3*R*) and (2*S*,3*S*) — a pair of enantiomers — and the *meso* form (2*R*,3*S*). The meso compound has an internal mirror plane, so it is identical to its mirror image (2*S*,3*R*) and is achiral.![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-f76e008ee0.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-bd41fd13d2.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-1ebab85cc8.svg) 9. Draw the stereoisomers of 1,2-dimethylcyclopropane. Which ones are chiral? ![Structure for the question](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-2bd2753230.svg) **3 stereoisomers:** *cis*-1,2-dimethylcyclopropane (meso, achiral — has a mirror plane) and the two enantiomers of *trans*-1,2-dimethylcyclopropane, (1*R*,2*R*) and (1*S*,2*S*), which are chiral.![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-2b4e7d9445.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-cf17c2d652.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-8326ba5d23.svg) 10. Which of these show cis/trans isomerism: (a) pent-1-ene, (b) pent-2-ene, (c) 2-methylbut-2-ene, (d) 1,2-dichloroethene? (b) pent-2-ene and (d) 1,2-dichloroethene. Pent-1-ene has two H atoms on C1, and 2-methylbut-2-ene has two CH3 groups on C2, so neither can form geometric isomers. moldraw.com/educational-materials/isomers-worksheet/ ## Answer key: Structural Isomers & Stereoisomers Worksheet ## Part A — Draw all the structural isomers 1. **3 isomers:** pentane; 2-methylbutane; 2,2-dimethylpropane.![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-d8bfc2ccb9.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-b5ee965b45.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-08eb63888c.svg) 2. **6 isomers** (5 structural + 1 extra stereoisomer): but-1-ene; (*Z*)-but-2-ene (cis); (*E*)-but-2-ene (trans); 2-methylpropene; cyclobutane; methylcyclopropane.![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-b24334aa53.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-0e4d74cd93.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-ce8f5b20a3.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-62b5354df5.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-18004bfa31.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-e4a73e19e0.svg) 3. **7 isomers.** Alcohols: butan-1-ol (1°); butan-2-ol (2°, chiral — exists as *R* and *S*); 2-methylpropan-1-ol (1°); 2-methylpropan-2-ol (3°). Ethers: 1-methoxypropane; 2-methoxypropane; ethoxyethane (diethyl ether).![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-069ca54449.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-7908c955ad.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-4560bdf298.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-8ec5351bef.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-ab8f118ba8.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-516c2cb206.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-0df3bfd023.svg) 4. (a) propanal (aldehyde) and propanone (acetone, ketone). (b) prop-2-en-1-ol (allyl alcohol); methoxyethene (methyl vinyl ether); cyclopropanol; oxetane; 2-methyloxirane (propylene oxide, chiral); plus the unstable enols prop-1-en-1-ol (*E*/*Z*) and prop-1-en-2-ol. **9 structural isomers in total** (7 if enols are excluded).![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-72e102d3b3.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-a2fe2176ee.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-adeb0f5b19.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-f47c23de60.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-98ba397abe.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-a6dd04aa7d.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-8556413b2b.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-5721bf2466.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-67ad3f0b3b.svg) 5. **3 isomers:** propan-1-ol; propan-2-ol; methoxyethane (ethyl methyl ether — the ether). The two alcohols are position isomers; the ether is a functional group isomer of them.![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-59d8b57bbf.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-35326b933c.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-6ec047cbd2.svg) ## Part B — Stereoisomers 6. Restricted rotation about C=C plus two *different* groups on *each* alkene carbon is needed. In but-2-ene each carbon carries H and CH3, giving (*Z*)-but-2-ene (cis, CH3 groups same side) and (*E*)-but-2-ene (trans). In but-1-ene, C1 carries two H atoms, so no geometric isomers exist.![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-0e4d74cd93.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-ce8f5b20a3.svg) 7. C2 (bonded to H, OH, CH3 and CH2CH3) is the chiral centre. The two non-superimposable mirror images are (*R*)-butan-2-ol and (*S*)-butan-2-ol.![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-d14035a13a.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-37ce944213.svg) 8. **3 stereoisomers:** (2*R*,3*R*) and (2*S*,3*S*) — a pair of enantiomers — and the *meso* form (2*R*,3*S*). The meso compound has an internal mirror plane, so it is identical to its mirror image (2*S*,3*R*) and is achiral.![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-f76e008ee0.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-bd41fd13d2.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-1ebab85cc8.svg) 9. **3 stereoisomers:** *cis*-1,2-dimethylcyclopropane (meso, achiral — has a mirror plane) and the two enantiomers of *trans*-1,2-dimethylcyclopropane, (1*R*,2*R*) and (1*S*,2*S*), which are chiral.![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-2b4e7d9445.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-cf17c2d652.svg)![Answer structure](https://www.moldraw.com/educational-materials/img/isomers-worksheet/s-8326ba5d23.svg) 10. (b) pent-2-ene and (d) 1,2-dichloroethene. Pent-1-ene has two H atoms on C1, and 2-methylbut-2-ene has two CH3 groups on C2, so neither can form geometric isomers. ## How to use this worksheet 1. Encourage a systematic approach: longest chain first, then shorten the chain by one carbon at a time and move the branch or functional group. 2. Students should name each isomer — two drawings with the same name are the same compound, which is the most common mistake. 3. Clarify whether a question wants constitutional (structural) isomers only or stereoisomers too; the answer key gives both counts. 4. Build the isomers in MolDraw and compare the generated names to spot duplicates. 5. Set the title, student lines and answer option on the left, then press **Download PDF** and choose “Save as PDF” (or print directly). Your choices are remembered on this device. **Draw and edit structures in MolDraw.** Make your own questions: draw any molecule, then export it as PNG or SVG for your worksheets. [Draw and edit structures in MolDraw](https://www.moldraw.com/) ## Frequently asked questions ### How many isomers does C5H12 have? C5H12 has three structural isomers: pentane, 2-methylbutane (isopentane) and 2,2-dimethylpropane (neopentane). None of them has stereoisomers. ### How many isomers does C4H10O have? C4H10O has 7 structural isomers: 4 alcohols (butan-1-ol, butan-2-ol, 2-methylpropan-1-ol, 2-methylpropan-2-ol) and 3 ethers (methoxypropane, 2-methoxypropane, ethoxyethane). Counting the two enantiomers of butan-2-ol gives 8 isomers in total. ### How many isomers does C4H8 have? C4H8 has 5 structural isomers (but-1-ene, but-2-ene, 2-methylpropene, cyclobutane and methylcyclopropane). But-2-ene exists as cis (Z) and trans (E) forms, so there are 6 isomers including stereoisomers. ### What is the difference between structural isomers and stereoisomers? Structural (constitutional) isomers have the same molecular formula but atoms joined in a different order. Stereoisomers have the same connectivity but a different 3-D arrangement, e.g. cis/trans isomers and enantiomers. ### Are the answers included? Yes. The answer key draws and names every isomer and explains each stereoisomer question. 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