Which of the following does not depict an isomer of oxetane
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → the structure containing two oxygen atoms
Isomers have the same molecular formula but different structures. Oxetane is a four-membered ring of three \( \ce{CH2} \) groups and one oxygen atom, so its formula is C3H6O. An isomer of oxetane must also have three C, six H and one O.
Option (1) 2-methyloxirane (propylene oxide), a three-membered ether ring carrying a \( \ce{CH3} \) group — An isomer of oxetane. Its formula is \( \ce{C3H6O} \).
Option (2) the open-chain structure drawn with two oxygen atoms — Not an isomer of oxetane. With two O atoms its formula cannot be \( \ce{C3H6O} \), so it does not have the same molecular formula.
Option (3) cyclopropanol, a three-membered carbon ring with an −OH group — An isomer of oxetane. Its formula is \( \ce{C3H6O} \).
Option (4) methoxyethene (methyl vinyl ether), \( \ce{CH2=CH-O-CH3} \) — An isomer of oxetane. Its formula is \( \ce{C3H6O} \).
Shortcut: Count the oxygen atoms first: only Option (2) has two.