DJA 3). Mechanisms

Question 1

free radical

Answer 1

A chemical species with an unpaired electron - usually highly reactive`

Question 2

how many stages to free radical substitution

Answer 2

3

Question 3

what are the stages of free radical substitution (short)

Answer 3

initiation propagation termination

Question 4

initiation

Answer 4

free radicals are produced

Cl₂ ——-> •Cl + •Cl

Question 5

Propagation

Answer 5

‘Recycling the free radical’

a) . Cl• + CH₃CH₃ ——–> CH₃•CH₂ + HCl (dot usually above C)
b) . CH₃•CH2 + Cl₂ —–> CH₃CH₂Cl + Cl •

free radical used and then reformed

Question 6

Termination

Answer 6

Two free radicals colliding

CH₃•CH₂ + Cl• ——->CH₃CH₂Cl

Cl• + Cl• ——–> NO JUST REFORMS WITH UV LIGHT

CH₃•CH₂ + CH₃•CH₂ ——-> CH₃CH₂CH₂CH₃

Question 7

Further substitution

Answer 7

If Cl₂ is in excess then the product will react with more and more Cl₂.

Then that new product wil react with more Cl₂ and so on….

Question 8

what is a nucleophile

Answer 8

a species that contains a lone pair of electrons

Question 9

3 examples of nucleophiles correctly written

Answer 9

negative (xx) OH

(xx) NH₃

negative (xx) CN

Question 10

What happens during nucleophlic substitution

Answer 10

The nucleophile will swap places with another nucleophile on a molecule

Question 11

Least reactive haloalkane

Answer 11

fluoro….

Question 12

most freactive haloalkane

Answer 12

iodo…..

Question 13

strongest haloalkane bond

Answer 13

fluoro….

Question 14

weakest haloalkane bond

Answer 14

iodo…

Question 15

explanation for strongest bond

Answer 15

shortest bond, electron pair in the bond is closest to the nucleus of F and there is little shielding therefore it is more strongly attracted

Question 16

explanation for weakest bond

Answer 16

longest bond, electron pair in covalent bond is further away from the nucleus and there is more shielding so held less strongly

Question 17

elimintaion

what does negative (xx) OH act as

Answer 17

a base