Select the chain propagation steps in the free radical chlorination of methane-1 Cl2 -2Cl2 -CH3 - -CH3- CH3 - CH33 -Cl - CH4 - CH3Cl - -Cl4 -CH3 - -Cl- CH3 - Cl5 -CH3 - Cl2 - CH3 - Cl - -Cl

In photochemical halogenation of alkane we have 3 steps, 1. Initiation nbsp; 2. Propagation 3. Termination nbsp; In initiation step, radicals of halogens a ...

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Standard XII

Chemistry

Nomenclature

Select the ch...

Question

Select the chain propagation steps in the free radical chlorination of methane.
$(1) C l_{2} \to ∙ 2 C l (2) ∙ C H_{3} + ∙ C H_{3} \to C H_{3} - C H_{3} (3) ∙ C l + C H_{4} \to C H_{3} C l + ∙ C l (4) ∙ C H_{3} + ∙ C l \to C H_{3} - C l (5) ∙ C H_{3} + C l_{2} \to C H_{3} - C l + ∙ C l$

2, 3, 5

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1, 3, 6

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3, 5

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2, 3, 4

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Solution

The correct option is C 3, 5
In photochemical halogenation of alkane we have 3 steps,
1. Initiation
2. Propagation
3. Termination

In initiation step, radicals of halogens are formed by homolytic cleavage. Here, the homolytic cleavage of $C l_{2}$ molecule takes place in the presence of heat or light because $C l - C l$ bond is weaker than $C - C$ and $C - H$ . Thus, $(1)$ is initiation step.

In propagation step, the product is formed by set of cyclic reaction. Here $(3)$ and $(5)$ are propagation steps which propagates the reaction.

In termination step, the reaction stops. This happens by the consumption of free radicals. Thus, no free radical is produced in termination step.
Thus $(2)$ and $(4)$ are termination step.

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Similar questions

Q. Which step is chain propagation step in the following mechanism?

C l_{2} h v - \to C l^{∙} + C l^{∙}

C l^{∙} + C H_{4} \to^{∙} C H_{3} + H C l

C l^{∙} + C l^{∙} \to C l_{2}

^{∙} C H_{3} +^{∙} C l \to C H_{3} C l

Q. Select the chain propagation steps in the free-radical chlorination of methane.
(1)

C l_{2} \to 2 C l^{\cdot}

(2)

C l^{\cdot} + C H_{4} \to C H_{3} C 1 + H^{\cdot}

(3)

C 1^{\cdot} + C H_{4} \to C H_{3}^{\cdot} + H C I

(4)

H^{\cdot} + C l_{2} \to H C l + C l^{\cdot}

(5)

C H_{3}^{\cdot} + C l_{2} \to C H_{3} C I + C l^{\cdot}

Q. Consider two alternative mechanism for the chlorination of methane. Which step is crucial in deciding which mechanism is not likely to be observed?
Mechanism I Mechanism II

A ${C l}_{2} ⟶ {2 C l}^{∙}$	A ${C l}_{2} ⟶ {2 C l}^{∙}$
B ${C l}^{∙} + {C H}_{4} ⟶ H C l +^{∙} {C H}_{3}$	D ${C l}^{∙} + {C H}_{4} ⟶ {C H}_{3} C l + H^{∙}$
C $∙ C H_{3} + {C l}_{2} ⟶ {C H}_{3} C l + {C l}^{∙}$	E $H^{∙} + {C l}_{2} ⟶ H C l + {C l}^{∙}$

Q. The decreasing order of rate of

S_{N} 2

reaction for given compounds is:

C H_{3} - C l

C H_{3} - C | | O - C H_{2} - C l

C H_{3} - C H | C H_{3} - C H_{3} - C l

C H_{3} - C H_{2} - C l

(I) (II) (III) (IV)

Q. Which of the following intermediate is formed, due to heterolytic cleavage of

C - C l

bond in

C H_{3} C l

molecule ?

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Select the chain propagation steps in the free radical chlorination of methane. (1)Cl2→∙2Cl(2)∙CH3+∙CH3→CH3−CH3(3)∙Cl+CH4→CH3Cl+∙Cl(4)∙CH3+∙Cl→CH3−Cl(5)∙CH3+Cl2→CH3−Cl+∙Cl