Original slide

prepared for the

Free Radical Substitution

Edexcel organic reaction mechanisms

Click a box below to go to the mechanism

Electrophilic Addition

Nucleophilic Substitution

Electrophilic Substitution

Nucleophilic Addition

Alkylation Acylation

Click here for advice

Heterolytic

Nitration

Free Radical Addition

Homolytic

Br2

SN1SN2

Original slide

prepared for the

CH4 + Cl2 CH3Cl + HCl

Overall reaction equation

Conditions

ultra violet lightexcess methane

i.e. homolytic breaking of covalent bonds

to reduce further substitution

Free radical substitution

chlorination of methane

Original slide

prepared for the

H3C

initiation step

two propagation steps

termination step

ultra-violet

CH3

minor termination step

Free radical substitution mechanism

Cl Cl

H3C H

Cl

Cl

H Cl

Cl Cl

Cl

H3C H3C Cl Cl

H3C Cl H3C Cl

H3C H3C CH3

Original slide

prepared for the

CH3Cl + Cl2 CH2Cl2 + HCl

Overall reaction equations

Conditions ultra-violet light

CH2Cl2 + Cl2 CHCl3 + HCl

CHCl3 + Cl2 CCl4 + HCl

excess chlorine

Further free radical substitutions

Original slide

prepared for the

n H2C=CH2

Overall reaction equation

polyethene

free radical source

i.e. homolytic breaking of covalent bonds

(a species that generates free radicals that allow the polymerisation of ethene molecules)

Free radical addition

addition polymerisation of ethene

[ CH2CH2 ]n

Conditions

ethene

Original slide

prepared for the

initiation step

Addition of H2C=CH2 repeats the same way until:

polyethene

Free radical addition mechanism

R R R R

R H2C CH2 H2C CH2 R

H2C CH2 H2C CH2R H2C CH2 CH2CH2R

R(CH2)nCH2

R(CH2)nCH2 CH2(CH2)mR

H2C(CH2)mR

chain propagation steps

termination step

Original slide

prepared for the

Electrophilic addition

CH3CH=CH2 + Br2 CH3CHBrCH2Br

bromine with propene

hydrogen bromide with but-2-ene

CH3CH=CHCH3+ HBr CH3CH2CHBrCH3

2-bromobutane

1,2-dibromopropane

mechanism

mechanism

Original slide

prepared for the

Br

Br

Br

Br

Electrophilic addition mechanism

CH3

H H

H

CC

+

-

CH3

H H

HCC

Br+

Br-

carbocation

CH3

H H

HCC

Br Br

1,2-dibromopropane

bromine with propene reaction equation

Original slide

prepared for the

Electrophilic addition mechanism

CH3

H CH3

H

CC

CH3

H H

CH3CC

H+

carbocation

CH3

H H

CH3CC

Br H

2-bromobutane

hydrogen bromide with trans but-2-ene

-

+

Br

H

reaction equation

Br-

Original slide

prepared for the

hydroxide ion with bromoethane

ethanolCH3CH2Br + OH- CH3CH2OH + Br-(aqueous)

Nucleophilic substitution

mechanism

hydroxide ion with 2-bromo,2-methylpropane

2-methylpropan-2-ol

(CH3)3CBr + OH- (CH3)3COH + Br-(aqueous)

mechanism

Original slide

prepared for the

+ -CH3

H

BrC

H

-OH

CH3

H

OHC

H Br-

hydroxide ion with bromoethane (SN2)

Nucleophilic substitution mechanism

ethanol

reaction equation

2(species reacting in the slowest step)

SN2

S (substitution)N(nucleophilic)

Original slide

prepared for the

+ -CH3

CH3

BrC

CH3

-OH

Br-

OH- ion with 2-bromo,2-methylpropane (SN1)

Nucleophilic substitution mechanism

2-methylpropan-2-ol

reaction equation

1(species reactingin the slowest step)

SN1

S (substitution)N(nucleophilic)

Br-

CH3

CH3

C

CH3

+ CH3

CH3

OHC

CH3

Original slide

prepared for the

Nucleophilic substitution

propanenitrile

CH3CH2I (ethanol) + CN-(aq) CH3CH2CN + I-

cyanide ion with iodoethane mechanism

cyanide ion with 2-bromo,2-methylpropane

2,2-dimethylpropanenitrile

(CH3)3CBr (ethanol) + CN-

(CH3)3CCN + Br-

(aqueous)

mechanism

Original slide

prepared for the

+ -CH3

H

IC

H

CN-

CH3

H

CNC

H I -

cyanide ion with iodoethane (SN2)

Nucleophilic substitution mechanism

propanenitrile

reaction equation

2(species reacting in the slowest step)

SN2

S (substitution)N(nucleophilic)

Original slide

prepared for the

+ -CH3

CH3

BrC

CH3

Br-

CN- ion with 2-bromo,2-methylpropane (SN1)

Nucleophilic substitution mechanism

2,2-dimethylpropanenitrile

1(species reactingin the slowest step)

SN1

S (substitution)N(nucleophilic)

Br-

CH3

CH3

C

CH3

+ CH3

CH3

CNC

CH3

CN-

reaction equation