STRUCTURAL INTEGRITY AND ISOMERISM OF ALKENES

The carbon atoms which contain the double bonds in alkenes are hybridized. Each carbon-carbon double bond is made of one sigma and one pi bond. 

More substituted alkenes are usually more stable than less substituted alkenes. 

Any compound with a carbon-carbon double bond can exhibit cis-trans isomerism, provided that the carbons involved in the double bond do not have two of the same groups or atoms attached to each of them. 2-Butene is the simplest alkene that can have cis-trans isomerism. Trans isomers are generally more stable than their cis counterparts. Alkyl groups are mildly electron-donating toward the double bond. This can lead to polarity. For instance, cw-2-butene has a net dipole moment as shown in the diagram given below. On the other hand, in trans-2-butene the net dipole is zero since the dipole moments cancel out (the vector sum of the dipole moments is zero). 

Both cis and rra s-2-butene have van der Waals attractive forces. But, only the cis-isomer can have dipole-dipole interactions because it has a net dipole moment. Hence, cw-2-butene has a higher boiling point than trans-2-butene. 

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