Tag: haloalkanes and haloarenes

Questions Related to haloalkanes and haloarenes

Which of the following Grignard reagent can be prepared? 

reactions of haloarenes haloalkanes and haloarenes chemistry

  1. $Br-Mg-{CH} _{2}-{CH} _{2}-{CH} _{2}O-H$

  2. $Br-Mg-{CH} _{2}-{CH} _{2}-SH$

  3. $BrMg-{CH} _{2}-{CH} _{2}-{NH} _{2}$

  4. $BrMg - CH _2- CH _2 - \underset{CH _3}{\underset{|}{N} -} CH _3$

Show answer
Correct Option: D
Explanation:
Grignards reagent form via the reaction of an alkyl or aryl halide with magnesium metal.The reaction is conducted by adding the organic halide to a suspension of magnesium in an ethyal solugnt,which produce the reaction proceeds through a single electron transfer as:
$R-X+mg\longrightarrow R-X^-+Mg^+$
$R-X^-\longrightarrow R+X^-$
$R+Mg^+\longrightarrow RMg^+$
$RMg^++X^-\longrightarrow RMgX$
Thus,by the above way of preparing grignard reagent,compounds with carbonyl group $(C=O)$,$-SH$ group and $-NH _2$ group cannot be prepared .

In which of the following reactions, products are not correctly matched in:

reactions of haloarenes haloalkanes and haloarenes chemistry

  1. $RMgX +{CO _{2}}\xrightarrow[(ii)H^{\bigoplus }]{(i)CO _{2}}$Carboxylic acid

  2. $RMgX + C _{2}H _{5}OH \rightarrow$ Alkane

  3. $RMgX+CH _{3}CH _{2}Cl\rightarrow$ Alkene

Show answer
Correct Option: C
Explanation:

Reaction:
$RMgX+CH _{3}CH _{2}Cl\rightarrow R-R$ alkane.

Propane dithioic acid is prepared by which of the following reactions, followed by hydrolysis:

reactions of haloarenes haloalkanes and haloarenes chemistry

  1. ${C} _{3}{H} _{7}MgBr+{CS} _{2}$

  2. ${C} _{2}{H} _{5}MgBr+{CS} _{2}$

  3. ${C} _{3}{H} _{7}MgBr+{SO} _{2}$

  4. ${C} _{2}{H} _{5}MgBr+{SO} _{3}$

Show answer
Correct Option: B
Explanation:

Propane dithioic acid is prepared by the reaction of the following, followed by hydrolysis of ${C} _{2}{H} _{5}MgBr+{CS} _{2}$
Hence option B is correct.

Which of the following reaction involves copper metal?

reactions of haloarenes haloalkanes and haloarenes chemistry

  1. Wurtz reaction

  2. Wurtz-Fittig reaction

  3. Ullmann reaction

  4. Frankland reaction

Show answer
Correct Option: C
Explanation:

Wurtz & Wurtz-Fittig reactions involve Sodium (Na) metal.


Frankland reaction involves Zinc or Magnesium (Zn or Mg) metal.

Ullmann reaction involves Copper (Cu) metal.

Option C is correct.

On reacting with which of the following chemicals sulphur undergoes combination reaction?

reactions of haloarenes haloalkanes and haloarenes chemistry

  1. metals

  2. nonmetals

  3. acids

  4. alkalies

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Correct Option: A,B
Explanation:

 On reacting with metals and non metals sulphur undergoes combination reaction.
$\displaystyle Fe+S \rightarrow FeS$
$\displaystyle Cl _2+2S \rightarrow S _2Cl _2$
Note:
A combination reaction (also known as a synthesis reaction) is a reaction where two or more elements or compounds (reactants) combine to form a single compound (product).

Which of the following statements is not correct?

polyhalogen compounds haloalkanes and haloarenes chemistry

  1. DDT and BHC are not good insecticides because they are highly soluble in water.

  2. DDT and BHC are not good insecticides because they are absorbed by the soil and contaminate root corps.

  3. Aldrin is not a good insecticide because it is not biodegradable.

  4. All of the above are incorrect.

Show answer
Correct Option: A
Explanation:

DDT and BHC 

both are good insecticides
since highly soluble in coater.

Match the column I with column II.

Columns I  Columns II 
A Carbon tetrachloride  i Paint remover 
B Methylene chloride  ii Refrigerators and air conditioners 
C DDT iii Fire extinguisher 
D Freons iv Non biodegradable insectiside 
polyhalogen compounds haloalkanes and haloarenes chemistry

  1. A=(ii), (B)=(iii), (C)=(i), (D)=(iv)

  2. A=(i), (B)=(ii), (C)=(iii), (D)=(iv)

  3. A=(iv), (B)=(iii), (C)=(ii), (D)=(i)

  4. A=(iii), (B)=(i), (C)=(iv), (D)=(ii)

Show answer
Correct Option: D
Explanation:

A) Carbon tetra-chloride is colorless, non inflammable and is used as a fire extinguisher. 

B) Methylene chloride is used as a paint remover. 
C) DDT is the chlorinated organic and non biodegradable insecticide. 
D) Freons are produced for aerosol propellants, refrigerators and air conditioners. 

0.0852 g of an organic halide (A) when dissolved in 2.0 g of camphor, the melting point of the mixture was found to be $167^{\circ}$C. Compound (A) when heated with sodium gives a gas (B). 280 mL of gas (B) at STP weighs 0.375g. What would be 'A' in the whole process? $K _f$ for camphor = 40, m.pt. of camphor = $179^{\circ}$C.

polyhalogen compounds haloalkanes and haloarenes chemistry

  1. $C _2H _5Br$

  2. $CH _3I$

  3. $(CH _3) _2CHI$

  4. $C _3H _7Br$

Show answer
Correct Option: B
Explanation:

$\delta$=179-167=12, w=0.0852g, W=2g,Kf= 40 
Moleculer weight of (A)
=$\dfrac{1000\times{Kf}\times{w} }{\delta{T}\times {W}}$
=$\dfrac{1000\times{40}\times{0.0852} }{\delta{12}\times {2}}$
=142
(A) undergoes wortz reaction to form (B) i.e
$(A)\rightarrow{Na} (B)+NaX$
(B) is an alkane say $C _nH _2n+2$
$\therefore$ 280 mL of (B) weighs 0.375 g at NTP
$\therefore$ 22400 mL of (B) weighs 
=$\dfrac{0.375\times{22400}}{280}$
=30 g at NTP
M.wt of (B)=30, 12n+2n+2=30,n=2
Thus (B) is ethane and therefore (A) is $CH _3X$
The m.wt of $CH _3X$=142
At.wt of X=127
$\therefore$ is iodine 
Therefore alkyl halide is $CH _3I$.
This reaction is 
2$CH _3I\xrightarrow[Na]{ether} C _2h _6$
(A)                         (B)

Breathing about 900 parts this substance per million parts of air for a short time cause dizziness heart & fatigue headache is-

polyhalogen compounds haloalkanes and haloarenes chemistry

  1. Methylene choride

  2. Chloroform

  3. Iodoform

  4. Tetra chlorometane

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Correct Option: B

Chloropicrin is ______.

polyhalogen compounds haloalkanes and haloarenes chemistry

  1. picric derivative

  2. nitrochloroform

  3. nitromethane

  4. nitroethyl chloride

Show answer
Correct Option: C