How can you identify cis and trans isomers?
Consider the following explanation.
Both of the isomers have exactly the same atoms joined up in exactly the same order .It means that the Van der Waals dispersion forces between the molecules will be identical in both cases.
The difference between the two is that the
2)Cis isomer due to being polar shows Dipole moment while the trans isomer does not.
Consider the case of 1,2-dichloroethene
In one, the two chlorine atoms are locked on opposite sides of the double bond. This is known as the trans isomer.
In the other, the two chlorine atoms are locked on the same side of the double bond. This is know as the cis isomer.
The effect of geometric/cis-trans isomerism on physical properties
cis 1,2-dichloroethene has a melting point of
In each case, the higher melting or boiling point is shown in red.
You will notice that:
the trans isomer has the higher melting point WHILE
the cis isomer has the higher boiling point.