Question

how many isomers does hexane (c₆h₁₄) have?
○ four
○ five
○ six
○ seven

Explanation:

To determine the number of structural isomers of hexane ($\ce{C6H14}$), we analyze the different arrangements of carbon atoms:

1. n - hexane (hexane): A straight - chain structure with 6 carbon atoms in a row: $\ce{CH3 - CH2 - CH2 - CH2 - CH2 - CH3}$.
2. 2 - methylpentane: One methyl group ($\ce{-CH3}$) is attached to the second carbon atom of a pentane (5 - carbon) chain. The structure is $\ce{(CH3)2CH - CH2 - CH2 - CH3}$.
3. 3 - methylpentane: A methyl group is attached to the third carbon atom of a pentane chain: $\ce{CH3 - CH2 - CH(CH3)-CH2 - CH3}$.
4. 2,2 - dimethylbutane: Two methyl groups are attached to the second carbon atom of a butane (4 - carbon) chain: $\ce{(CH3)3C - CH2 - CH3}$.
5. 2,3 - dimethylbutane: Methyl groups are attached to the second and third carbon atoms of a butane chain: $\ce{(CH3)2CH - CH(CH3)2}$.

Counting these distinct structural isomers, we get a total of 5.

Answer:

B. five