Cis and Trans Isomers of 2-Butene

Figure 6.3, page 182

The two cis-trans isomers of 2-butene are shown below. You can rotate the structures with your mouse. By clicking the right mouse button, you can access a menu to change the display style. Click on DISPLAY and then choose the type of model that you want.

cis-2-Butene

trans-2-Butene

The cis-isomer (or Z-isomer) has the two methyl groups on the same side of a line that runs through the doubly bonded carbons. The steric crowding between the methyl groups causes the cis-stereoisomer to be slightly less stable than the trans-stereoisomer. This steric strain can be better seen in a space-filling model. The trans-isomer (or E-isomer) has the two methyl groups on opposite sides of a line that runs through the doubly bonded carbons. There is no steric interaction between the methyl groups, so the trans-stereoisomer is slightly more stable than the cis-stereoisomer.

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