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Organic Chemistry

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Aromatic Compounds

Question
11 out of 16
 

The earliest predictions about the structure of benzene could not completely explain some of its properties. Later it was found that benzene has a cyclic structure which is commonly represented as follows:

image\27771 ch 18 passage 1.png

These two structures are resonance structures of benzene. Benzene is also commonly represented as shown below:

image\27782 ch 18 passage 1.png

A series of reactions were conducted using benzene and other aromatic compounds.

Reaction 1

In Reaction 1, benzene was reacted with n-propyl chloride in the presence of AlCl3.

Reaction 2

Nitrobenzene was reacted with nitric acid and sulfuric acid. The reaction occurred as follows:


image\Ch 18 pass react 2.png


Which of the following is true regarding Reaction 1 described in the passage?

A It is a Friedel-Crafts acylation reaction
B It is a reaction which results in a single product
C AlCl3 acts as a Lewis base
D Rearrangement is possible
Ans. D This reaction is a Friedel-Crafts alkylation reaction. This rules out Choice A. In an alkylation reaction, there is a possibility of rearrangement. The primary alkyl halide (n-propyl chloride) can form secondary carbocations by rearrangement. To avoid this type of rearrangement, chemists often use Friedel-Crafts acylation reactions which do not involve rearrangement. The carbonyl group in the acylation product can be easily reduced to get the desired hydrocarbon.

Aromatic Compounds Flashcard List

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