Question

Name the following compound:

A.5-ethyl-trans-5-octene
B.5-ethyl-cis-5-octene
C.4-ethyl-trans-3-octene
D.4-ethyl-cis-3-octene

Answer 1

Hint: To answer this question, we should know the correct process to name organic compounds by following the norms of IUPAC nomenclature. We should know the difference between cis and trans organic molecule, then only we can give correct answer of this compound.

Step by step answer:
We should first correctly know about cis or trans isomerism. We should know that cis–trans isomerism, also known as geometric isomerism. So, for now we will understand cis-trans isomerism in very simple language. We should note that cis indicates that the functional groups are on the same side of the carbon chain while trans conveys that functional groups are on opposing sides of the carbon chain.
So, if we look at the structure that is given in question we should note that ethyl groups are present on the opposite sides. So, from this we can say that this is trans structure. It means that our correct option is from option A and C. Now, we should look at the structure and observe that the ethyl group is attached to fourth carbon. And the double bond is on third carbon. We should correctly number the carbon atoms in the structure. The structure with correct numbering of carbon atoms is presented below:

So, by looking at the above structure, now we know the correct name of this organic compound. The correct answer of this organic compound is 4-ethyl-trans-3-octene. Option C is correct.

Note: We should know to select the longest chain of carbon atoms in the molecule. We should note that when chains of equal lengths are competing for selection, then we should select that chain which has more number of substituents.