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

In the case of cycloalkane, if the two substituents point toward the same faces, they are known as cis isomers. Again, if the two substituents point toward the opposite faces, they are known as trans-isomers. These two geometric isomers cannot interconvert without breaking and forming the bonds again.

Axial bonds are directed vertically parallel to the axis of the ring, and the equatorial bonds are directed outward from the equator of the ring. As the carbon atoms are numbered in cyclohexane, it can be seen that the odd-numbered carbons have their upward bonds in theaxial position and their downward bonds in the equatorial position. The even-numbered carbons have their downward bondsin theaxial position and their upward bonds in the equatorial position.

The axial position is shown by a solid blue line, and theequatorial position is shown by asolid red line in the structures drawn.

$\text{ci}s−1,2\text{ â¶Ä‰}(a,e)$$\text{ci}s−1,2\text{ â¶Ä‰}(e,a)$

$trans−1,2\text{ â¶Ä‰}(a,a)$$trans−1,2\text{ â¶Ä‰}(e,e)$

$\text{ci}s−1,3\text{ â¶Ä‰}(a,a)$$\text{ci}s−1,3\text{ â¶Ä‰}(e,e)$

$trans−1,3\text{ â¶Ä‰}(a,e)$$trans−1,3\text{ â¶Ä‰}(e,a)$

$\text{ci}s−1,4\text{ â¶Ä‰}(a,e)$$\text{ci}s−1,4\text{ â¶Ä‰}(e,a)$

$trans−1,4\text{ â¶Ä‰}(a,a)$$trans−1,4\text{ â¶Ä‰}(e,e)$