Tag: reactions of haloarenes

Questions Related to reactions of 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. $BrMg - CH _2- CH _2 - \underset{CH _3}{\underset{|}{N} -} CH _3$

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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

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

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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

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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).