Question

What type of reaction is `CH_3CH_3 + Cl_2 → CH_3CH_2Cl + HCl`?

Answer 1

This is actually a multi-step mechanism for a radical chlorination of ethane. You can always tell by knowing you are starting with an alkane and are reacting with a diatomic halogen. There are no other "standard" reactions like this.

OVERALL

`color(blue)("CH"_3"CH"_3 + "Cl"_2 stackrel(Delta, "or "hnu" ")(->) "CH"_3"CH"_2"Cl" + "HCl")`

The reaction mechanism is shown below.

INITIATION STEP

`color(blue)("Cl"_2) stackrel(Delta, "or "hnu" ")(=>) 2"Cl"cdot`

PROPAGATION STEPS

`color(blue)("CH"_3"CH"_2"H") + cdot"Cl" => "CH"_3"CH"_2cdot + color(blue)("HCl")`

`"CH"_3"CH"_2cdot + color(blue)("Cl"_2) => color(blue)("CH"_3"CH"_2"Cl") + "Cl"cdot`

TERMINATION STEPS

`"H"_3"C"-"CH"_2cdot + cdot"H"_2"C"-"CH"_3 => "CH"_3"CH"_2"CH"_2"CH"_3`

`"Cl"cdot + cdot"Cl" => color(blue)("Cl"_2)`

`"CH"_3"CH"_2cdot + "Cl"cdot => color(blue)("CH"_3"CH"_2"Cl")`

Note that all of this occurs until the all reactant is consumed, so don't fret over the fact that what is shown here does not explicitly demonstrate conservation of mass.

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You can see a more detailed version here, but for bromine with propane instead of chlorine with ethane.