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Chapter 2: Problem 130

When ethylene gas is passed into a mixture of an aqueous solution of bromine and sodium chloride, the products formed are \(\mathrm{BrCH}_{2} \mathrm{CH}_{2} \mathrm{Br}, \mathrm{BrCH}_{2} \mathrm{CH}_{2} \mathrm{OH}\) and \(\mathrm{BrCH}_{2} \mathrm{CH}_{2} \mathrm{Cl}\). Justify the formation of these products by giving a suitable mechanism.

Short Answer

Expert verified
Question: Explain how 1,2-dibromoethane, 2-bromoethanol, and 2-bromochloroethane can be formed from the reaction of ethylene gas with a mixture of an aqueous solution of bromine and sodium chloride. Answer: The formation of these products occurs through the initial formation of a bromonium ion intermediate. This positively charged intermediate is attacked by various nucleophiles in the solution, such as bromide ions (forming 1,2-dibromoethane), water molecules (forming 2-bromoethanol), and chloride ions (forming 2-bromochloroethane).

Step by step solution

01

Reaction of ethylene with bromine

When ethylene gas (C2H)_4) is passed into a mixture of an aqueous solution of bromine (Br2), the double bond in ethylene attacks the bromine molecule, causing it to form a cyclic bromonium ion. This intermediate has a positive charge and is highly reactive. The intermediate can be represented as follows: C2H4 + Br2 -> [Br-CH2-CH2-Br]+
02

Attack of the bromide ion on the bromonium ion

In the solution, there are bromide ions (Br-) present. These bromide ions can attack the bromonium ion, opening the cyclic structure and forming the product 1,2-dibromoethane (BrCH2CH2Br). This is an example of a nucleophilic attack on an electrophilic intermediate. [Br-CH2-CH2-Br]+ + Br- -> BrCH2CH2Br
03

Formation of 2-bromoethanol

The bromonium ion can also be attacked by water molecules present in the solution. This would lead to the formation of 2-bromoethanol (BrCH2CH2OH). This is another example of a nucleophilic attack on an electrophilic intermediate. [Br-CH2-CH2-Br]+ + H2O -> BrCH2CH2OH
04

Formation of 2-bromochloroethane

In the presence of sodium chloride (NaCl), there are chloride ions (Cl-) in the solution. These chloride ions can also attack the bromonium ion, forming the product 2-bromochloroethane (BrCH2CH2Cl). This reaction occurs less frequently, as bromide ions are better nucleophiles than chloride ions. [Br-CH2-CH2-Br]+ + Cl- -> BrCH2CH2Cl In conclusion, the formation of 1,2-dibromoethane, 2-bromoethanol, and 2-bromochloroethane occurs through the initial formation of a bromonium ion intermediate, which is a positively charged species that can be attacked by various nucleophiles in the solution, such as bromide ions, water molecules, and chloride ions.

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Most popular questions from this chapter

A hydrocarbon \(\mathrm{C}_{5} \mathrm{H}_{12}\) (A) on treatment with chlorine undergoes monochlorination by the replacement of the only \(1^{\circ}\) hydrogen to give(B) \(\mathrm{C}_{5} \mathrm{H}_{11} \mathrm{Cl}\). When (B) is treated with Na metal in ether, the product obtained could be (a) \(\quad\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CH}-\mathrm{CH}\left(\mathrm{CH}_{3}\right)_{2}\) (b) \(\mathrm{CH}_{3}-\mathrm{C}\left(\mathrm{CH}_{3}\right)_{2}-\mathrm{C}\left(\mathrm{CH}_{3}\right)_{2}-\mathrm{CH}_{3}\) (c) \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{C}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{C}\left(\mathrm{CH}_{3}\right)_{3}\) (d) \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{C}-\mathrm{CH}_{2} \mathrm{Cl}\)

(a) Write the structure of organic product formed by heating \(\mathrm{C}\left(\mathrm{CH}_{2} \mathrm{I}\right)_{4}\) with zinc dust. (b) How is buta- 1,3 -diene prepared from but- 1 -ene (c) What are the products expected when ethylene is passed into an aqueous solution of bromine containing dissolved sodium chloride?

Which of the following compounds can exhibit geometrical isomerism? (a) \(\mathrm{IBrC}=\mathrm{CFCI}\) (b) Cinnamic acid (c) Benzophenone oxime (d)

\(\mathrm{CH}_{3}-\mathrm{CH}=\mathrm{CH}_{2}+\mathrm{Br}_{2} \rightarrow(\mathrm{A}) \stackrel{\mathrm{NaNH}_{2}}{\longrightarrow}(\mathrm{B}) \stackrel{\mathrm{H}^{+}}{\longrightarrow}(\mathrm{C}) .\) The structure of (C) is (a) \(\mathrm{CH}_{3} \mathrm{C} \equiv \mathrm{CH}\) (b) \(\mathrm{H}_{3} \mathrm{C}-\mathrm{C} \equiv \mathrm{C}-\mathrm{CH}_{3}\) (c) \(\mathrm{BrCH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2} \mathrm{Br}\) (d) \(\mathrm{H}_{2} \mathrm{C}=\mathrm{C}=\mathrm{CH}_{2}\)

Identify the name of reactions (A) - (D) given below (A) \(2 \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{I} \stackrel{\text { Na /ether }}{\longrightarrow} \mathrm{C}_{4} \mathrm{H}_{10}+2 \mathrm{NaI}\) (B) (C) \(\mathrm{R}_{2} \mathrm{CuLi} \stackrel{\mathrm{R}^{\prime} \mathrm{X}}{\longrightarrow} \mathrm{R}-\mathrm{R}\) (D) \(\mathrm{CH}_{3}-\mathrm{CO}-\mathrm{CH}_{3} \stackrel{\mathrm{Zn}-\mathrm{Hg} / \mathrm{HCl}}{\longrightarrow} \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{3}\) (a) (A) Ulmann reaction (B) Electrolytic cleavage (C) Grignard reaction (D) Wolff-kishner reduction (b) (A) Wurtz reaction (B) Kolbe's electrolysis (C) Corey-House synthesis (D) Clemmensen reaction (c) (A) Wurtz reaction (B) Decarboxylation (C) Frankland reaction (D) Clemmensen reduction (d) (A) Wurtz-Fittig reaction (B) Decarboxylative coupling (C) Corey-House synthesis (D) Clemmensen reduction
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