Looking for classes? Ksquare Career Institute, Bengaluru →
Which of the following compounds will exhibit cis-trans (geometrical) isomerism?
A
1-Butanol
B
2-Butene
C
2-Butanol
D
2-Butyne
Detailed Solution
Cis–trans isomerism needs restricted rotation (a C=C double bond or a ring) and two different groups on each of the doubly bonded carbon atoms.
2-Butene, $CH_3-CH=CH-CH_3$: each doubly bonded carbon has one H and one $CH_3$, so cis and trans forms exist.
1-Butanol and 2-butanol have only single bonds with free rotation (2-butanol shows optical, not geometrical, isomerism).
2-Butyne, $CH_3-C\equiv C-CH_3$, is linear about the triple bond, and each triply bonded carbon has only one substituent.
Hence 2-butene exhibits cis–trans isomerism.
2-Butene, $CH_3-CH=CH-CH_3$: each doubly bonded carbon has one H and one $CH_3$, so cis and trans forms exist.
1-Butanol and 2-butanol have only single bonds with free rotation (2-butanol shows optical, not geometrical, isomerism).
2-Butyne, $CH_3-C\equiv C-CH_3$, is linear about the triple bond, and each triply bonded carbon has only one substituent.
Hence 2-butene exhibits cis–trans isomerism.