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Functional Isomerism

Ethers are he...

Question

Ethers are heated with excess of conc. hydrogen halide to give alkyl halide, then the reactivity order of hydrogen halide is :

A

H C l < H B r < H F

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B

H I > H B r > H C l

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C

H F < H C l < H B r

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D

none of these

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Solution

The correct option is B $H I > H B r > H C l$
When $H X$ is in excess and reaction is carried out at high temperature. Iodine is a good nucleophile, displaces an alcohol molecule by $S N^{2}$ mechanism thus $H I > H B r > H C l$

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Similar questions

Q. The correct order of thermal stability of hydrogen halides (H – X) is

Q. Arrange in decreasing order of acid strength.

H F, H C l, H B r, H I

Q. The variation of the boiling points of the hydrogen halides is in the order

H F > H I > H B r > H C l

. What explains the higher boiling point of hydrogen fluoride?

Q. Carbon - oxygen bond in ethers can be cleaved by halogen acids, sulphuric acid, phosphorouspentachloride etc. The cleavage of

C - O

bond takes place under drastic conditions with excess of hydrogen halide,

R - O - R + 2 H X \to H X \to 2 R X + H_{2} O

If hydrogen halide is not taken in excess, then one molecule each of alcohol and alkyl halide are formed,

R - O - R + H I 373 K \to R - O H + R - I

. The order of reactivity of hydrogen halides towards the above mentioned reaction depends on the bond strength of halogenated acids. Weaker is the

H - X

bond, greater is its reactivity. In case of unsymmetrical ethers, the site of cleavage is such that the halide is formed from the alkyl group which is tertiary, so that the halide formed is tertiary halide.

Indicate whether the following statements / reactions are true or false.
The order of hydrogen halide reactivity is

H I < H B r < H C l

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