Nomenclature and Isomerism of Alkenes - Practice Questions & MCQ

Nomenclature of Alkenes
The general rules and principles of the IUPAC nomenclature are already discussed in the earlier chapter. Here we will discuss some common examples to the naming them.

IUPAC name: Octa-1,3,5,7-tetraene

IUPAC name: 2-n-propylpent-1-ene

Isomerism
Alkenes show two kinds of isomerism i.e, stereoisomerism and geometrical isomerism

• Stereoisomerism: Ethene (C2H4) and propene (C3H6) can have only one structure but alkenes higher than propene have different structures.For example, But-1-ene can have three different structures as follows:
  
                           
   
• Geometrical isomerism: When the groups attached to doubly bonded carbon atoms are different, they can be represented with different geometries. This type of isomerism is known as geometrical isomerism. The two structures or isomers are known as cis and trans isomers. 
  
  NOTE: The trans isomer has strong close packing than the cis isomer, thus the melting point of trans isomer is higher than the cis isomer. Further, the molecules of the cis isomer are loosely held thus they are more soluble in the particular solvent than the trans isomer.