How do you write a stepwise mechanism that shows how a small amount of $C H_{3} C H_{3}$ $CH_3CH_3$ could form during the bromination of #CH_4?

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How do you write a stepwise mechanism that shows how a small amount of $C H_{3} C H_{3}$ $CH_3CH_3$ could form during the bromination of #CH_4?

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Answer 1 · 2016-09-07T07:34:48

Bromination proceeds by a radical mechanism, in which $B r \cdot$ $Br*$ radicals are invoked. So let's see.

Explanation:

$Initiation:$ $"Initiation:"$ $B r_{2} + h ν \to 2 B r \cdot$ $Br_2 +hnu rarr2Br*$

$Propagation:$ $"Propagation:"$ $B r \cdot + C H_{4} \to \cdot C H_{3} + H - B r$ $Br* +CH_4 rarr*CH_3 + H-Br$

$B r_{2} + \cdot C H_{3} \to B r C H_{3} + B r \cdot$ $Br_2 +*CH_3 rarr BrCH_3 + Br*$

$Termination:$ $"Termination:"$ $B r \cdot + B r \cdot \to B r_{2}$ $Br* + Br* rarr Br_2$ , i.e. the coupling of 2 radicals could occur, or the coupling of hydrocarbyl radicals made in the propagation step:

$H_{3} C \cdot + \cdot C H_{3} \to H_{3} C - C H_{3}$ $H_3C*+*CH_3 rarr H_3C-CH_3$

And thus the coupling of 2 methyl radicals results in $C - C$ $C-C$ bond formation.

Overall, the bromination rxn is:

$C H_{4} + B r_{2} \to C H_{3} B r + H - B r$ $CH_4 + Br_2 rarr CH_3Br + H-Br$

The discovery of ethane in the reaction mixture is good evidence for the radical reaction as shown.

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How do you write a stepwise mechanism that shows how a small amount of $C H_{3} C H_{3}$ $CH_3CH_3$ could form during the bromination of #CH_4?

1 Answer

Explanation:

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How do you write a stepwise mechanism that shows how a small amount of CH3CH3CH_3CH_3 could form during the bromination of #CH_4?

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Explanation:

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How do you write a stepwise mechanism that shows how a small amount of $C H_{3} C H_{3}$ $CH_3CH_3$ could form during the bromination of #CH_4?