Which of the following compounds has only primary and secondary hydrogen atoms?
A 2-Methylpentane
B) 2,2,3-Trimethylpentane
C3-Methylpentane
D 2,2-Dimethylpentane
The correct answer and explanation is:
The correct answer is A) 2-Methylpentane.
To explain, let’s break down the hydrogen atoms in each compound and categorize them as primary, secondary, or tertiary:
- Primary hydrogen atoms are attached to a carbon atom that is bonded to only one other carbon.
- Secondary hydrogen atoms are attached to a carbon atom bonded to two other carbons.
- Tertiary hydrogen atoms are attached to a carbon atom bonded to three other carbons.
A) 2-Methylpentane
- The structure of 2-methylpentane involves a five-carbon chain (pentane) with a methyl group (–CH₃) attached to the second carbon.
- The primary carbon atoms are those that are attached to only one other carbon (i.e., the ends of the chain).
- The secondary carbon atoms are those attached to two other carbon atoms (i.e., the second carbon in the chain where the methyl group is attached).
- There are no tertiary hydrogen atoms, as there are no carbons bonded to three other carbons.
B) 2,2,3-Trimethylpentane
- In 2,2,3-trimethylpentane, the carbon chain has three methyl groups attached (two at the second carbon and one at the third carbon).
- This structure includes tertiary hydrogen atoms because the second carbon (where two methyl groups are attached) is bonded to three other carbons. These hydrogens are on tertiary carbons, making the compound have tertiary hydrogens.
C) 3-Methylpentane
- The structure of 3-methylpentane has a methyl group attached to the third carbon of the pentane chain. This also includes a tertiary hydrogen, similar to 2,2,3-trimethylpentane.
D) 2,2-Dimethylpentane
- This structure has two methyl groups attached to the second carbon of the pentane chain, creating tertiary hydrogen atoms, as the second carbon is attached to three other carbons.
Therefore, 2-methylpentane is the only compound in the list that has only primary and secondary hydrogen atoms.