Question

The name of the alkane isomer of cis-3-hexene is:
A. 2-methylpentane
B. 3-methylpentane
C. n-hexane
D. cyclohexane

Answer 1

Hint: To answer this question we need to know the molecular formula of all the compounds. Knowing the structure can make the task simpler and you can get to the answer easily and quickly. With the formula we can count the number of carbon and hydrogen atoms and comparing it with cis-3-hexene we can get the answer.

Step by step answer: To answer this question, we need to understand isomerism and alkane isomer. Isomerism is the phenomenon in which more than one compound has the same chemical formula but different chemical structures. Chemical compounds that have identical chemical formulas but have different properties and the arrangement of atoms in the molecule are called isomers. There are two types of isomerism which are Structural isomerism and Stereoisomerism. Structural isomerism can be further divided into chain, position and functional isomers and Stereoisomers can be divided into geometric and optical isomers. Structural isomerism refers to the compounds that differ in their connectivity between the atoms and stereo isomerism refers to the compounds with same exact molecular formula and connectivity but differ in the arrangement of atoms in three dimensional space.
Alkane means compounds consisting of hydrogen and carbon atoms arranged in a structure in which all the carbon-carbon bonds are single. Therefore, alkane isomers are hydrogen and carbon compounds that have isomeric properties. Now, to answer this question we need to know the structure and molecular formula of cis-3-hexene. Its molecular formula is $$C_6{H}_{14}$$ . Given below is the structure of cis-3-hexane.

Now, let’s see the structure and molecular formula of compounds given in options.
2-methylpentane ( $$C_6{H}_{14}$$ )

3-methylpentane ( $$C_6{H}_{14}$$ )

n-hexane ( $$C_6{H}_{14}$$ )

Cyclohexane ( $$C_6{H}_{12}$$ )

From the structure of the compounds and the molecular formula we get to know that Cyclohexane has the same molecular formula as cis-3-hexene. Therefore, alkane isomer of cis-3-hexene is cyclohexane. Here, we can see that both cyclohexane and cis-3-hexene have same molecular formula but different structures. Therefore, satisfying the property of isomerism especially structural isomerism.
Therefore, the answer is option D.

Note: The structure and molecular formula are an important part of organic chemistry. Every prefix used in naming is different and helps determine its structure. Understanding the meaning of the prefixes is also important.