Which of the following describes 'Hexane, Heptane, Octane, Nonane'?

• A. They are alkynes
• B. They are isomers
• C. They are alkanes
• D. They are cyclic compounds

Answer: (C)

Hexane, heptane, octane, and nonane are all examples of alkanes, which are a class of hydrocarbons characterized by having only single bonds between carbon atoms. They all follow the general formula CnH2n+2, where "n" is the number of carbon atoms. Specifically, hexane has six carbon atoms, heptane has seven, octane has eight, and nonane has nine. Their structure is linear and they do not contain any double or triple bonds, which aligns with the definition of alkanes.

The naming of these compounds also reflects their saturation and the number of carbons, further confirming that they fit into the alkane category. This unique structure contributes to their stability and explains their presence in various applications, from fuels to solvents.

In contrast, the other answer choices do not accurately categorize these compounds. Alkynes, characterized by triple bonds, isomer refers to compounds with the same molecular formula but different arrangements, and cyclic compounds are those that form rings. Thus, the defining feature of hexane, heptane, octane, and nonane is that they are all unbranched alkanes, making them members of the alkane family.