[jena]

Hi, I have a question that states:

What is the enthalpy diffence (within 1 kcal/mole) for the second propagation step of the reaction of 3-methylpentane, chlorine, and light going to the major product of this reaction?

I really don't know how to approach the problem. Please help.

Thank you  

[Mitch]

Do you know what the product will be?

[jena]

The answer that the teacher gave us is -25, but I still don't understand how to set-up. Please tell me if what i have so far is wrong:
                                                                       
C₅(CH₃) + Cl₂ -----> C₅H₃  Cl + CH₃Cl

Is this first step right  

Thank You  

[dexangeles]

do you know what kind of reaction will take place?

[jena]

What do you mean by what reaction will take place?

Again please help  

[Mitch]

This is a radical halogenation. With Cl going to the tertiary carbon and HCl given off. Now can you write the equation for it?

[dexangeles]

isn't it a free radical chlorination (halogenation)?

[jena]

Hi is it written like this

C5H12(CH3) + Cl2 -------> C5H11(CH3)Cl + HCl

Thank you

[Mitch]

looks good to me.

[dexangeles]

that's the reaction summary
free radical chlorination of 3-methylpentane forms 3-chloro-3-methylpentane

now you need to find the propagation step
hint: there's 3 steps to free radical halogenation