Tag: preparation of haloalkanes

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Multiple choice preparation of haloalkanes halogen derivatives carbon tetrachloride ddt

In the following reaction, identify the compound A.
$3CH _3-CH _2-OH+A\rightarrow 3C _2H _5-Cl+H _3PO _3$.

  1. $PCl _3$
  2. $PCl _5$
  3. $POCl _3$
  4. $H _2PO _2$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A is $PCl _3$ in the above reaction.
$3CH _3-CH _2-OH+PCl _3\rightarrow 3C _2H _5-Cl+H _3PO _3$
Hence option A is corrcet.

Multiple choice preparation of haloalkanes halogen derivatives carbon tetrachloride ddt

By the action of $PCl _3$ or $PCl _5$ with alcohols alkyl halides and a by product $HCl$ is formed.The byproduct HCl is absorbed by using :

  1. $Et _3N,C _5H _5N$
  2. $Et _2NH,C _5H _5N$
  3. $Et _NH _2,C _5H _5N$
  4. $Et _3N,C _6H _5N$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

By the action of $PCl _3$ or $PCl _5$ with alcohols alkyl halides and a
by product $HCl$ is formed.The byproduct $HCl$ is absorbed by using Triethyl amine($Et _3N$),pyridine($C _5H _5N$) which are bases and neutralise the acid like $HCl$ and $HBr$ etc.

Multiple choice preparation of haloalkanes halogen derivatives carbon tetrachloride ddt

Trimethyl amine used for _______ in  the preparation of alkyl halide from alchohol and phosphorous halide.

  1. the absorption of hydrogen halide

  2. the release of Hydrogen halide

  3. as the catalyst

  4. none
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Trimethyl amine and pyridine used for the absorption of hydrogen halide.in  the preparation of alkyl halide from alchohol and phosphorous halide.As these two are bases which can neutralize the acids like $HCl$ and $HBr$
Hence option A is correct.

Multiple choice preparation of haloalkanes halogen derivatives carbon tetrachloride ddt

What is the product formed when $CH _3CH _2CH _2CH _2-OH$ is reacted with $PCl _3$ in presence of trimethyl amine?

  1. $CH _3CH _2CH _2CH _2-Cl$
  2. $CH _3CH(CH _3)CH _2CH _2-Cl$
  3. $CH _3CH _2C(CH _3) _2CH _2-Cl$
  4. $CH _3CH _2CH _2CH _2CH _2CH _2-Cl$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When Alcohol reacts with $PCl _{3}$ in presence of Trimethyl Amine. It is a nucleophile substitution halogenation reaction replaces $OH^{-}$  with $Cl^{-}$  

   $CH _{3}CH _{2}CH _{2}CH _{2} - OH\overset{PCl _{3}}{\rightarrow} CH _{3}CH _{2}CH _{2}CH _{2} - Cl $

Multiple choice preparation of haloalkanes halogen derivatives carbon tetrachloride ddt

$3C _2H _5OH+A\rightarrow C _2H _5Br+H _3PO _3$.Which of the following is A ?

  1. $PBr _3$
  2. $PBr _5$
  3. $POBr _3$

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The reagent used in the above reaction is $PBr _3$
$3CH _3-CH _2-OH+PBr _3\rightarrow 3C _2H _5-Cl+H _3PO _3$
Hence option A is correct.

Multiple choice preparation of haloalkanes halogen derivatives carbon tetrachloride ddt

$CH _3CH _2C(CH _3) _2CH _2-OH+PCl _3\rightarrow A+H _3PO _4$. In the above reaction which of the following is A?

  1. $CH _3CH _2C(CH _3) _2CH _2-Cl$
  2. $CH _3CH _2CH(CH _3)CH _2-Cl$
  3. $CH _3CH _2CH _2CH _2-Cl$
  4. $CH _3CH(CH _3)C(CH _3) _2CH _2-Cl$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$CH _3CH _2C(CH _3) _2CH _2-OH+PCl _3\rightarrow CH _3CH _2C(CH _3) _2CH _2-Cl+H _3PO _4$
So in the above reaction A is $CH _3CH _2C(CH _3) _2CH _2-Cl$
Hence option A is correct.

Multiple choice preparation of haloalkanes halogen derivatives carbon tetrachloride ddt
Consider the following reaction:
$R-OH+PX _5\rightarrow R-X+B+HX$ 
What is B?
  1. $HPOX _3$
  2. $H _3PO _2$
  3. $H _3PO _3$
  4. $POX _3$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

B is $ \displaystyle POX _3$.
For example, when ethyl alcohol is refluxed with $ \displaystyle PCl _5$, ethyl chloride, HCl and phosphorous oxy chloride is obtained.
$ \displaystyle CH _3-CH _2-OH +PCl _5 \to CH _3-CH _2-Cl+POCl _3+HCl$

Multiple choice preparation of haloalkanes halogen derivatives carbon tetrachloride ddt

Bases like tri-ethyl amine and pyridine are used to:

  1. mop up the acidic byproduct

  2. crystallize alkyl halide

  3. evaporate alkyl halide

  4. none
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Bases like tri-methyl amine and pyridine are used to mop up the acidic byproduct and make it neutral.
Hence option A is correct.

Multiple choice preparation of haloalkanes halogen derivatives carbon tetrachloride ddt

Alkyl bromide is prepared by heating alcohol with ______ phosphorus in the presence of bromine gas.

  1. black

  2. white

  3. red

  4. none of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Alkyl Bromide is prepared by heating alcohol with Red phosphorous in the presence of Bromine gas.

$CH _3-OH \xrightarrow{Red\ P/Br _2} CH _3-Br$