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Hydrocarbons

Long Answer Type

221. Write a short note on Friedel Craft’s reaction ?

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222. Discuss the important addition reactions of benzene.

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223.
Discuss the oxidation reactions of arenes.

Arenes are quite stable and not readily oxidised. Some of their oxidation reactions are:

(i) Combustion: When burnt in oxygen, benzene and other hydrocarbons burn with a smoky flame and produce carbon dioxide and water.

(ii) Oxidation of benzene: When a mixture of air and vapours of benzene is passed over vanadium pentoxide (V₂O₅) at 773 K, maleic anhydride is produced.

(iii) Oxidation of the side chain.
(a) With weak oxidising agent. Toluene is oxidised to benzaldehyde by using chromyl chloride (CrO₂Cl₂) or acidic manganese dioxide.

(b) With normal oxidising agent. On oxidation with a strong oxidising agent such as hot KMnO₄, concentrated HNO₃, acidified KMnO₄ or acidified dichromate etc., the entire side chain, regardless of length, is oxidised to - COOH group.

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Short Answer Type

224.

Write chemical equations for the combustion reaction of the following hydrocarbons:
Butane

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225.

Write chemical equations for the combustion reaction of the following hydrocarbons:
Pentene

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226.

Write chemical equations for the combustion reaction of the following hydrocarbons:
Hexyne

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227.

Write chemical equations for the combustion reaction of the following hydrocarbons:
Toluene

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228.

Write down the products of ozonolysis of 1, 2-dimethylbenzene (o-xylene). How does the result support Kekule structure for benzene?

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229. What happens when:

Benzene is treated with acetic anhydride in the presence of anhydrous AlCl₃.

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230. What happens when:

Toluene is heated with a mixture of concentrated nitric acid and concentrated sulphuric acid at 303 K.

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