Question

How can you distinguish between cis and trans isomers?

Answer 1

The cis-isomer are the type of isomers where the similar atoms are present on the same side of the double bond. The trans-isomers are the type of isomers where the similar atoms are present on the opposite side of the double bond.

Complete answer:
Isomers are defined as the compounds which have the same molecular formula but they differ in the arrangement of atoms.
The cis-isomers and trans-isomers are types of isomers where the number of atoms and the molecular formula are same but the atoms or the group are arranged differently.
In the cis-isomer, the two same type of atoms are placed on the same side of the double bond. In the trans-isomer, the two same types of atoms are placed opposite sides of the double bond.
Cis and trans isomer are distinguished from each other as shown below.
Cis-isomer:
(1) In cis-isomers, the similar atoms are placed on the same side of the double bond.
(2) Cis-isomer are usually polar in nature.
(3) In cis-isomers, the atoms are loosely packed, thus the cis-isomers are usually have lower meltig point than the trans-isomer.
(4) In cis-isomer, strong attractive force is present between atom so it has higher boiling point than trans-isomer.
Trans-isomer:
(1) In trans-isomers, the two similar atoms are attached opposite to the double bond.
(2) The trans-isomers are usually non-polar in nature.
(3) In trans-isomer, the atoms are tightly packed, thus the trans-isomer have higher melting point than the cis-isomer.
(4) In trans-isomer, no strong attractive force is present between the atoms, so the boiling point of trans-isomer is lower than the cis-isomer.

Note:
The isomers are mainly divided into constitutional isomers and stereoisomers. The cis-isomer and trans-isomer are shown by alkenes which are represented as $R - CH = CH - R$ where R is the alkyl group.