(N/A) The structure of $hex-2-ene$ is $CH_3-CH=CH-CH_2-CH_3$.
The geometrical isomers are:
$Cis-hex-2-ene$: The two alkyl groups ($CH_3$ and $CH_2CH_3$) are on the same side of the double bond.
$Trans-hex-2-ene$: The two alkyl groups ($CH_3$ and $CH_2CH_3$) are on opposite sides of the double bond.
The $cis$-isomer has a net dipole moment because the bond dipoles of the alkyl groups reinforce each other. In the $trans$-isomer,the bond dipoles partially cancel each other out,resulting in a lower net dipole moment.
Since the $cis$-isomer is more polar,it experiences stronger intermolecular dipole-dipole interactions. Therefore,the $cis$-isomer has a higher boiling point than the $trans$-isomer.