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Karnataka Board PUCPUC Science 2nd PUC Class 12

Why is sulphuric acid not used during the reaction of alcohols with KI? - Chemistry

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Question

Why is sulphuric acid not used during the reaction of alcohols with KI?

Chemical Equations/Structures
Short Answer

Solution

\[\ce{2KI + H2SO4 -> 2KHSO4 + 2HI}\]

\[\ce{2HI + H2SO4 -> 2H2O + I2 + SO2}\]

In these reactions, H2SO4 is an oxidising agent. It oxidises the HI formed during the reaction to I2 and prevents the formation of alkyl halide by the reaction of HI and alcohol. To overcome this problem, phosphoric acid (H3PO4) is used instead of H2SO4, which provides HI for the reaction and does not give I2 like H2SO4.

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Methods of Preparation of Haloalkanes
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Chapter 10: Haloalkanes and Haloarenes - Intext Questions [Page 289]

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NCERT Chemistry [English] Class 12
Chapter 10 Haloalkanes and Haloarenes
Intext Questions | Q 6.2 | Page 289

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