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Questions Related to ddt

An organic halide ,${C _2}{H _4}C{l _2}$ gives an unsaturated hydrocarbon on treatment with aloc .KOH,but ethanal on reaction with aq. KOH, the halide is:

preparation of haloalkanes halogen derivatives carbon tetrachloride ddt

  1. $C{H _3}CHC{l _2}$

  2. $C{H _2}ClC{H _2}Cl$

  3. a mixture of (a) and (b)

  4. none of these

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Correct Option: B

Preparation of alkylhalides by the reaction of alcohols and phosporous halide is _____ reaction.

preparation of haloalkanes halogen derivatives carbon tetrachloride ddt

  1. nucleophilic substitution

  2. electrophilic substitution

  3. addition

  4. elimination

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Correct Option: A
Explanation:

Preparation of alkylhalides by the reaction of alcohols and phosporous halide is nucleophilic substitution Reaction.
Becuase the nucleophile halide ion from phosporous halide like $PX _3,PX _5$  substitutes the $OH^{-}$ ion in alcohol, which is called as nucleophilic substitution reaction
e.g. $3CH _3-CH _2-OH+PCl _3\rightarrow 3C _2H _5-Cl+H _3PO _3$
Hence option A is correct.

For the preparation of chloroethane,

preparation of haloalkanes halogen derivatives carbon tetrachloride ddt

  1. $HCl$ gas is passed through ethanol.

  2. ethanol is treated with thionyl chloride in the presence of dimethyl amine or pyridine.

  3. ethyl sulphide is treated with hydrogen chloride.

  4. any of the above methods can be employed.

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Correct Option: B
Explanation:

${C} _{2}{H} _{5}OH\xrightarrow [  ]{ SO{ Cl } _{ 2 } }  {C} _{2}{H} _{5}Cl+{SO} _{2}+HCl$
(a). $HCl$ bond is strong, no reaction.

$C _2H _5OH+PCl _5\rightarrow $
In the above reaction which of the following alky halide is formed?

preparation of haloalkanes halogen derivatives carbon tetrachloride ddt

  1. $C _2H _5-Cl$

  2. $C _2H _5CH _2-Cl$

  3. $C _2H _5CH _2CH _2-Cl$

  4. None of the above

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Correct Option: A
Explanation:

$C _2H _5-Cl$ is the alkyl halide formed in the above reaction
$C _2H _5OH \ + \ PCl _5 \longrightarrow C _2H _5Cl \ + \ POCl _3 \ + \ HCl$
Hence option A is correct.

$R-OH+PCl _5\rightarrow A+B+C$.Identify A,B & C.

preparation of haloalkanes halogen derivatives carbon tetrachloride ddt

  1. $RCl+POCl _2+HCl$

  2. $R-Cl+POCl _3+HCl$

  3. $R-Cl+POCl+HCl$

  4. $C _2H _5Cl+POCl _3+PCl _3$

Show answer
Correct Option: B
Explanation:

A,B,C are $R-Cl,POCl _3,HCl$
$R-OH+PCl _5\rightarrow R-Cl+POCl _3+HCl$
Hence option B is correct.

In the given reaction, identify the compound A.
$3C _2H _5OH+PBr _3\rightarrow A+H _3PO _3$.

preparation of haloalkanes halogen derivatives carbon tetrachloride ddt

  1. $C _2H _5Br$

  2. $CH _3C _2H _5Br$

  3. $CH _2CH _2CH _2CH _2-Cl$

  4. None of the above

Show answer
Correct Option: A
Explanation:

A is $C _2H _5Br$
$3CH _3-CH _2-OH+PBr _3\rightarrow 3C _2H _5-Br+H _3PO _3$

In the following reaction, identify the compound A.
$3CH _3-CH _2-OH+PCl _3\rightarrow 3C _2H _5-Cl+A$ .

preparation of haloalkanes halogen derivatives carbon tetrachloride ddt

  1. $H _3PO _2$

  2. $H _3PO _3$

  3. $H _3PO _4$

  4. $POCl _3$

Show answer
Correct Option: B
Explanation:

A is $H _3PO _3$
$3CH _3-CH _2-OH+PCl _3\rightarrow 3C _2H _5-Cl+H _3PO _3$
Hence option A is correct.

Which of the following is the byproduct when $R-OH$ is reacted with $PCl _3$?

preparation of haloalkanes halogen derivatives carbon tetrachloride ddt

  1. $POCl _3$

  2. $H _3PO _3$

  3. $HCl$

  4. None of these

Show answer
Correct Option: B
Explanation:


$H _3PO _3$ is the byproduct when R-Cl is reacted with $PCl _3$

$3R-OH+PCl _3\rightarrow R-Cl+ H _3PO _3$

In the final product, we get a byproduct of $H _3PO _3$

Hence option B is correct.

In the given reaction, the product formed A and B are :
$3CH _3-CH _2-OH+PCl _3\rightarrow A+B$

preparation of haloalkanes halogen derivatives carbon tetrachloride ddt

  1. $3C _2H _5-Cl+H _2O$

  2. $3C _2H _5-Cl+HCl$

  3. $3C _2H _5-Cl+H _3PO _3$

  4. $3C _2H _5-Cl+POCl _3$

Show answer
Correct Option: C
Explanation:

The products formed are $3C _2H _5-Cl+H _3PO _3$ when $3CH _3-CH _2-OH$ is reacted with $PCl _3$.


$3CH _3-CH _2-OH+PCl _3\rightarrow 3C _2H _5-Cl+H _3PO _3$
Hence option C is correct.



In the following reaction which of the following are byproducts?
$C _2H _5OH+PCl _5\rightarrow $

preparation of haloalkanes halogen derivatives carbon tetrachloride ddt

  1. $POCl _3, HCl$

  2. $POCl _2, HCl$

  3. $PCl _3, HCl$

  4. None

Show answer
Correct Option: A
Explanation:

When ethanol reacts with phosphorous pentachloride, we get ethyl chloride as the main product whereas, phosphorous oxychloride and HCl as the byproducts.