free radical substitution (+ intro to mechanisms)

ew

what is a haloalkane?

an alkane where at least 1 H atom has been replaced w/ a halogen atom

what is the product of free rad sub?

haloalkanes

what is a mechanism?

process showing the step by step movement of e^- as reactants are converted into products

what does a single headed curly arrow represent?

movement of a single e^-

what does a double headed curly arrow represent?

movement of an e^- pair

what is a free radical?

a molecule w/ an odd no. of e^- and so an unpaired e^-

how reactive are free radicals?

very reactive!

name the steps of free rad sub:

1. initiation

2. propagation

3. termination

give the overall eqn for the reaction of methane w/ chlorine:

CH₄ + Cl₂ → CH₃Cl + HCl

describe and give the eqn for the initiation step of free rad sub of the reaction of methane w/ chlorine:

• UV light breaks Cl molecules into free radicals by providing the E to break the Cl-Cl bond

• Cl : Cl → . Cl + . Cl

which side are the radicals on in initiation?

RHS

describe and give the eqn for the propagation step of free rad sub of the reaction of methane w/ chlorine:

• Cl radicals react w/ alkanes in a chain reaction where the Cl radical acts as a catalyst

• for each H replaced, there is a pair of propagation steps

• . Cl + CH₄ → HCl + . CH₃

• . CH₃ + Cl₂ → CH₃Cl + . Cl

which side are the radicals on in propagation?

both sides

describe and give the eqns for the termination step of free rad sub of the reaction of methane w/ chlorine:

• when any 2 free radicals meet, they react to form a molecule w/ no unpaired e^-, stopping the chain reaction

• . Cl + .Cl → Cl₂

• OR . Cl + . CH₃ → CH₃Cl

• OR . CH₃ + . CH₃ → C₂H₆