Chapter 3: Q17P (page 168)

Question: Which of the following cycloalkanes are capable of geometric (cis-trans) isomerism? Draw the cis and trans isomers
(a) $3 - ethyl - 1,1 - dimethylcyclohexane$
(b) $1 - ethyl - 3 - methylcycloheptane$
(c) $1 - ethyl - 3 - methylcyclopentane$
(d) $1 - cyclopropyl - 2 - methylcyclohexane$

Short Answer

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Step by step solution

Step-by-Step solutionStep 1:Cis- and trans-isomers

Cis- and trans-isomerism can be used only for the compounds in which two doubly bonded carbon atoms are having similar atoms or groups. When the similar atoms or groups lie on the same side, it is called as cis-isomer and when similar atoms or groups lie on the opposite sides, it is called as trans-isomer. These two geometric isomers cannot interconvert without breaking and forming the bonds again.

Step 2:Drawing cis- and trans-isomers for cycloalkanes

In case of cycloalkane, if the two substituents point toward the same faces, then they are known as cis isomer. Again, if the twosubstituents point toward the oppositefaces, then they are known astrans isomer. These two geometric isomers cannot interconvert without breaking and forming the bonds again.