mechanisms 1

Question 1

(free radical substitution) Methane reacts vigorously with chlorine gas in the presence of UV light, as represented by the equation: (4)
write the equations and give the names

Answer 1

1) Stage 1 - Initiation
UV light breaks the Cl-Cl bond in chlorine via homolytic fission to give two chlorine radicals (Cl*):
Cl2 ➔ 2Cl *

2) Stage 2 - Propagation
The chlorine radical attacks a methane molecule in a substitution reaction:
Cl* + CH4 ➔ CH3* + HCl
The methyl radical (CH3) attacks another chlorine molecule:
CH3 + Cl2 ➔ CH3Cl + Cl*
This propagation cycle continues until reagents are used up.

3) Stage 3 - Termination
Two radicals join to form a stable covalent bond:
Cl* + CH3* ➔ CH3Cl
Other combinations like 2CH3* ➔ C2H6 or 2Cl* ➔ Cl2 are also possible.
4) The end products of the termination step depend on which reagent is in excess:
Excess chlorine - Further substitution on products like chloromethane occurs, producing a mixture of products such as CH3Cl, CH2Cl2, CHCl3, and CCl4.
Excess methane - Predominantly single substitution occurs to form chloromethane.

Question 2

( nucleophilic substitution) bromoethane reacts with cyanide to form … : (draw mechanism)

Answer 2

ethanenitrile https://cognitoedu.org/coursesubtopic/c3-alevel-aqa_PwogFJjU

Question 3

( nucleophilic substitution) bromoethane reacts with ammonia to form… : (draw mechanism)

Answer 3

ethylamine
https://cognitoedu.org/coursesubtopic/c3-alevel-aqa_PwogFJjU

Question 4

(elimination reaction)
2-iodopropane reacts with OH- : (draw mechanism)

Answer 4

propene
https://cognitoedu.org/coursesubtopic/c3-alevel-aqa_gjGLXoJA