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4-nitromethylbenzene can be prepared via an electrophilic substitution reaction as shown - CIE - A-Level Chemistry - Question 6 - 2017 - Paper 1
Question 6
4-nitromethylbenzene can be prepared via an electrophilic substitution reaction as shown. (i) This reaction also forms an isomer of 4-nitromethylbenzene as a by-pro... show full transcript
Worked Solution & Example Answer:4-nitromethylbenzene can be prepared via an electrophilic substitution reaction as shown - CIE - A-Level Chemistry - Question 6 - 2017 - Paper 1
Step 1
Draw the structure of this by-product.
Answer
The isomer of 4-nitromethylbenzene that is formed as a by-product is 2-nitromethylbenzene. Its structure can be represented as follows:
CH₃
\
C₆H₄
//
NO₂
This indicates that the nitro group (NO₂) is positioned at the 2-position relative to the methyl group (CH₃) on the benzene ring.
Step 2
Step 3
Describe how the structure and bonding of the six-membered ring in intermediate T differs from that in methylbenzene.
Answer
In intermediate T, the six-membered ring contains a nitro group (NO₂) and exhibits partial positive character due to the influence of the electron-withdrawing nature of the nitro group. This results in changes in its structure and bonding compared to methylbenzene, which has only a methyl group (CH₃).
Key differences include:
- Bonds: In intermediate T, bonds are partially delocalized, while in methylbenzene, they are fully delocalized in the aromatic system.
- Electrons: Intermediate T has four π-electrons that are involved in bonding compared to methylbenzene which has six single electrons available for delocalization.
- Hybridization: In T, at least one carbon participating in bonding may show signs of sp² hybridization due to the presence of the nitro group, affecting bond angle and hybrid characteristics in comparison to all carbon atoms in methylbenzene which are also sp² hybridized but less affected by an electron-withdrawing group.