Write structures for the three isomers of the aromatic hydrocarbon xylene

Write structures for the three isomers of the aromatic hydrocarbon xylene, C6H4(CH3)2.

The correct answer and explanation is :

The three isomers of xylene (C₆H₄(CH₃)₂) are:

1. Ortho-xylene (1,2-dimethylbenzene)
2. Meta-xylene (1,3-dimethylbenzene)
3. Para-xylene (1,4-dimethylbenzene)

Structural Formulas:

1. Ortho-xylene:
   In ortho-xylene, the two methyl groups (-CH₃) are positioned adjacent to each other on the benzene ring at positions 1 and 2.
   The structure can be written as:

        CH₃      CH₃
         |        |
    C₆H₄(CH₃)₂

2. Meta-xylene:
   In meta-xylene, the two methyl groups are positioned with one carbon atom between them on the benzene ring at positions 1 and 3.
   The structure is:

         CH₃    CH₃
          |      |
     C₆H₄(CH₃)₂

3. Para-xylene:
   In para-xylene, the two methyl groups are located opposite each other on the benzene ring at positions 1 and 4.
   The structure is:

         CH₃
          |
    C₆H₄(CH₃)₂
          |
         CH₃

Explanation:

Xylene is a type of aromatic hydrocarbon and isomeric in nature, meaning it can exist in several forms depending on the relative positioning of the two methyl groups on the benzene ring. The key feature of these isomers is the different placements of the two -CH₃ groups on the six-carbon benzene ring.

1. Ortho-xylene: The methyl groups are adjacent to each other, which is why it is named “ortho.” This form often leads to steric strain due to the close proximity of the two methyl groups.
2. Meta-xylene: The methyl groups are separated by one carbon, giving it the “meta” designation. The distance between the methyl groups is somewhat larger compared to ortho-xylene, which reduces steric hindrance.
3. Para-xylene: The methyl groups are placed opposite each other, at positions 1 and 4. This arrangement minimizes steric strain and is considered the most stable form due to its symmetrical structure.

Each of these isomers has different physical and chemical properties due to the varying spatial arrangements of the substituent methyl groups on the aromatic ring. These variations in molecular structure result in distinct melting points, boiling points, and other properties.