Question

Which of the following is not a straight-chain hydrocarbon?

• A.

  

• B.

  

• C.

  

• D.

  

Answer 1

The correct option is D

Explanation for correct option

(D)

Straight-chain hydrocarbons

• Straight-chain hydrocarbons are one class of organic compounds that don't have a substituent attached to the parent hydrocarbon chain.
• Straight-chain alkanes are termed by adding the suffix -ane, which denotes that the molecule is an alkane.

• Although there are six carbon atoms in total in this chemical, pentane has the longest continuous hydrocarbon chain.
• The second carbon atom in the chain has one methyl substituent attached to it.
• This compound isn't a straight-chain compound.
• This compound is a branched-chain compound.
• IUPAC name of this compound is $2-\mathrm{methyl}\mathrm{pentane}$.

Explanation for incorrect options

• The given structures are as follows:

• Six carbon atoms in total are found in these compounds.
• The compounds only contain hexane which has the longest continuous hydrocarbon chain.
• All the structures are the different arrangements of hexane.
• On the chain, there are no attached substituents.
• As a result, this compound has a straight chain.
• Hence, all other options (A), (B), and (C) are incorrect.

Therefore, the correct option is (D).