Total number of isomers, considering both structural and stereoisomers of cyclic ethers with the molecular formula C₄H₈O is
ChemistryClass 11CBSEAnswered 22 May 2026
Answer
Degree of unsaturation = (2×4 + 2 − 8) / 2 = 1 → One ring, no double bonds.
A cyclic ether contains one O atom inside the ring. Possible ring sizes: 3-membered (oxirane), 4-membered (oxetane), 5-membered (tetrahydrofuran).
| Structure | Isomer Count |
| 2,2-dimethyloxirane | 1 |
| (R)-ethyloxirane | 1 |
| (S)-ethyloxirane | 1 |
| cis-2,3-dimethyloxirane (meso) | 1 |
| (R,R)-2,3-dimethyloxirane | 1 |
| (S,S)-2,3-dimethyloxirane | 1 |
| 3-methyloxetane | 1 |
| Tetrahydrofuran (THF) | 1 |
Answer: 8 isomers
Always check for stereocentres in epoxide rings. The meso compound of 2, 3-dimethyloxirane is a frequent JEE trap.
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