Class Functional gp Suffix Example Formula

Alkane C - C - ane ethane CnH2n+2

H H

׀ ׀

H - C – C – H

׀ ׀

H H

H ׀

H - C – H

׀ H

H H H

׀ ׀ ׀

H - C – C – C – H

׀ ׀ ׀

H H H

H H H H

׀ ׀ ׀ ׀

H - C – C – C – C – H

׀ ׀ ׀ ׀

H H H H

Number carbon

Word IUPAC name

Structure formula Molecular formula

1 Meth Methane CH4 CH4

2 Eth Ethane CH3CH3 C2H6

3 Prop Propane CH3CH2CH3 C3H8

4 But Butane CH3(CH2)2CH3 C4H10

5 Pent Pentane CH3(CH2)3CH3 C5H12

6 Hex Hexane CH3(CH2)4CH3 C6H14

7 Hept Heptane CH3(CH2)5CH3 C7H16

8 Oct Octane CH3(CH2)6CH3 C8H18

9 Non Nonane CH3(CH2)7CH3 C9H20

10 Dec Decane CH3(CH2)8CH3 C10H22

methane ethane propane butane

Saturated hydrocarbon (C – C single bond)

Chemical rxn Alkane Reactivity for Alkanes

Combustion rxn

Complete combustion – produce CO2 + H2O • C2H6 + 7/2O2 → 2CO2 + 3H2O Incomplete combustion – produce C, CO, CO2, H2O • 2C3H8 + 7O2 → 2C + 2CO + 8H2O + 2CO2

Free Radical Substitution rxn

Free Radical Substitution Mechanism

- Homolytic fission- bond break by radical form. - Covalent bond split, each atom obtain one electron (unpair e) - UV needed

- Radical react with molecule

- Radical + radical → molecule

CH4 + CI2 → CH3CI + HCI

• Low reactivity - Strong stable bond bet C - C, C - H • Low reactivity - Low polarity of C - H bond • Saturated hydrocarbon – Non polar bond

Initiation

Propagation

Radical (dot)

Termination

homolytic fission

Radical recycle again

1

2

H H

׀ ׀

C = C

׀ ׀

H H

H H H

׀ ׀ ׀

C = C – C - H

׀ ׀

H H

H H H H

׀ ׀ ׀ ׀

C = C – C – C - H

׀ ׀ ׀

H H H

Unsaturated hydrocarbon (C = C double bond)

H H H H H

׀ ׀ ׀ ׀ ׀

C = C – C – C – C - H

׀ ׀ ׀ ׀

H H H H

ethene propene butene pentene

Reactivity for Alkene

- High reactivity - Unstable bond bet C = C - High reactivity – Weak pi bond overlap bet p orbital - Unsaturated hydrocarbon – ᴨ bond overlap

Combustion rxn

Chemical rxn Alkane

Complete combustion – produce CO2 + H2O C2H4 + 3O2 → 2CO2 + 2H2O Incomplete combustion – produce C, CO, CO2, H2O 2C2H4 + 7/2O2 → 2C + CO + 4H2O + CO2

CH2 = CH2 + Br2 → CH2BrCH2Br CH2 = CH2 + HCI → CH3CH2CI CH2 = CH2 + H2O → CH3CH2OH

Addition rxn

H H

׀ ׀

C = C

׀ ׀

H H

H H

׀ ׀

H - C – C – H

׀ ׀

CI CI

Class Functional Suffix Example Formula

Alkene Alkenyl - ene ethene CnH2n

H H

׀ ׀

H - C – C – H

׀ ׀

Br Br

H H

׀ ׀

H - C – C – H

׀ ׀

H CI

H H

׀ ׀

H - C – C – H

׀ ׀

H OH

1

2

Polymerization (Addition rxn) 3

Polymers are long chains molecules (plastics) • Join repeat units call monomers • Addition and condensation polymerization

• Monomers double bond (unsaturated) • Repeat units join together by covalent bond without loss of any molecule

ethene polyethene

add monomer

polymer

propene polypropylene

add monomer

H CH3 H CH3

monomer

monomer

chloroethene polychloroethene (PVC)

tetrafluoroethene polytetrafluoroethene (PTFE)

H CI H CI

F F

F F

F F

F F

polymerization

polymer

Alkene decolourize brown liq Br2

OH

׀ CH3-C – CH3 + [O] No product ׀ CH3

OH O

‖ ׀ CH3- C–CH3 + [O] CH3- C – CH3 + H2O

H

׀

CH3 – C – OH

׀

H

Class Functional Suffix Example Formula

Alcohol Hydroxyl - ol methanol CnH2n+1OH

Number carbon

IUPAC name Structure formula Molecular

formula

1 Methanol CH3OH CH3OH

2 Ethanol CH3CH2OH C2H5OH

3 Propanol CH3CH2CH2OH C3H7OH

4 Butanol CH3(CH2)2CH2OH C4H9OH

methanol ethanol propanol butanol

H

׀

H - C – OH

׀

H

H H

׀ ׀

H - C – C – OH

׀ ׀

H H

H H H

׀ ׀ ׀

H - C – C – C – OH

׀ ׀ ׀

H H H

H H H H

׀ ׀ ׀ ׀

H - C – C – C – C – OH

׀ ׀ ׀ ׀

H H H H

Hydrocarbon skeleton Functional gp

Chemical rxn Alcohol Reactivity for Alcohol

Primary 1 0

1 alkyl /R gp bond to C attach to OH

CH3 H

׀ ׀

CH3 – C – C – OH

׀ ׀

CH3 H

Combustion rxn

Complete combustion–produce CO2 + H2O C2H6OH + 3O2 → 2CO2 + 3H2O Incomplete combustion-produce C, CO, CO2, + H2O 2C2H5OH + 4O2 → C + 2CO + 6H2O + CO2

Oxidation rxn

Secondary 2 0

2 alkyl/R gp bond to C attach to OH

H

׀

CH3 – C – OH

׀

CH3

H H H

׀ ׀ ׀

H - C – C – C – H

׀ ׀ ׀

H OH H

Tertiary 3 0

3 alkyl/R gp bond to C attach to OH

CH3

׀

CH3 – C – OH

׀

CH3

R

׀

R – C – OH

׀

R

H ׀ CH3-CH2-OH + [O] CH3- C = O + H2O MnO4

- /H

+

K2Cr2O7/H+

Primary 10 – Oxidised to Aldehyde and Carboxylic acid

H OH ׀ ׀ CH3- C= O + [O] CH3-C= O

Secondary 20 - Oxidised to Ketone

Tertiary 30 - Cannot be Oxidised

MnO4- /H

+

K2Cr2O7/H+

MnO4- /H

+

K2Cr2O7/H+

MnO4- /H

+

K2Cr2O7/H+

1

1

Esterification rxn 3

O H

׀ ‖

H - C – O – C – H + H2O

׀

H

H

׀

H- O – C – H

׀

H

O

‖

H - C – O-H +

Chemical rxn Alcohol

Oxidation rxn – oxidized carbon attach to OH

Primary 10 – Oxidised to Aldehyde and Carboxylic acid

Secondary 20 - Oxidised to Ketone Tertiary 30 - Cannot be Oxidised

OH

׀ CH3-C – CH3 + [O] No product ׀ CH3

MnO4- /H

+

K2Cr2O7/H+

MnO4- /H

+

K2Cr2O7/H+

MnO4- /H

+

K2Cr2O7/H+

Alcohol to Aldehyde (Distillation) 1. Acidified dichromate(VI)/permanganate(VII)

2.Warm it , collect distillate (Distillation)

Aldehyde Carboxylic acid

-1 + 1

ON carbon increase Alcohol

H OH ׀ ׀

CH3- C= O + [O] CH3- C =O

H H ׀ ׀

CH3- C -O-H + [O] CH3- C = O

׀ H

+ 1 + 3

ON carbon increase Aldehyde

Primary 10 – Oxidised to Aldehyde and Carboxylic acid

Alcohol to Carboxylic acid (Reflux) 1. Acidified dichromate(VI)/permanganate(VII)

2.Warm it , collect distillate (Distillation)

Alcohol oxidize to Aldehyde • MnO4

- reduce from purple (Mn7+) to pink (Mn2+) • Cr2O7

2- reduce from orange (Cr6+) to green (Cr3+)

0 + 2

ON carbon increase Alcohol Ketone

Alcohol to Ketone (Reflux) 1. Acidified dichromate(VI)/permanganate(VII)

2.Warm it , collect distillate (Distillation) Click here oxidation alcohol

RCH2OH + [O] → RCHO + H2O RCH2OH + 2[O] → RCOOH + H2O RCH(OH)R + [O] → RCOR + H2O

Oxidation eqn (addition of O)

Aldehyde Alcohol

Alcohol

Alcohol

Carboxylic acid

Ketone

Alcohol oxidize to Carboxylic acid • MnO4

- reduce from purple (Mn7+) to pink (Mn2+) • Cr2O7

2- reduce from orange (Cr6+) to green (Cr3+)

distillation

reflux

Aldehyde turn to carboxylic acid

Aldehyde Alcohol

reflux

Alcohol turn to ketone

OH O

‖ ׀

CH3- C – CH3 + [O] CH3- C – CH3 + H2O

Class Functional Suffix Formula

Ester Ester - oate R –COO-R

Number carbon

IUPAC name Structure formula Molecular formula

1 Methyl methanoate HCOOCH3 R–COO-R

2 Methyl ethanoate CH3COOCH3 R–COO-R

3 Methyl propanoate CH3CH2COOCH3 R–COO-R

4 Methyl butanoate CH3CH2CH2COOCH3 R–COO-R

methyl methanoate methyl ethanoate methyl propanoate

O H

׀ ‖

H - C – O – C - H

׀

H

H O H

׀ ‖ ׀

H - C - C – O - C - H

׀ ׀

H H

H H O H

׀ ‖ ׀ ׀

H - C – C – C – O - C - H

׀ ׀ ׀

H H H

Hydrocarbon skeleton Functional gp

Esterification

O

‖

H - C – O-H

H

׀

H- O – C – H

׀

H

O H

׀ ‖

H - C – O – C – H + H2O

׀

H

Ester

Condensation rxn

↔ +

Methanoic acid Methanol Methyl methanoate

Esterification (reversible rxn) After reflux – reach equilibrium

Acid and alcohol (reflux) Conc H2SO4 (catalyst) used

Water produced

condensation

reflux

Ester purified and distill Click here ester preparation

H O H

׀ ‖ ׀

H - C - C – O - C – H + H2O

׀ ׀

H H

H

׀

H- O – C – H

׀

H

H O

‖ ׀

H - C - C – OH

׀

H

CH3COOH + CH3OH → CH3COOCH3 + H2O

H O H H

׀ ׀ ‖ ׀

H – C – C– O - C–C-H

׀ ׀ ׀

H H H

+

Ethanoic acid Methanol Methyl ethanoate

↔

H H

׀ ׀

H- O- C– C – H

׀ ׀

H H

H O

‖ ׀

H – C – C - OH

׀

H

condensation

CH3COOH + CH3CH2OH → CH3COOCH2CH3 + H2O

+

condensation

↔

Ethanoic acid Ethanol Ethyl ethanoate

+ H2O

H

׀

CH3 – C – CI

׀

H

H

׀

H - C – CI

׀

H

H H

׀ ׀

H - C – C – CI

׀ ׀

H H

H H H

׀ ׀ ׀

H - C – C – C – CI

׀ ׀ ׀

H H H

Hydrocarbon skeleton Functional gp

Primary 1 0

1 alkyl /R gp bond to C attach to CI

Secondary 2 0

2 alkyl/R gp bond to C attach to CI

H

׀

CH3 – C – CI

׀

CH3

H H H

׀ ׀ ׀

H - C – C – C – H

׀ ׀ ׀

H CI H

Tertiary 3 0

3 alkyl/R gp bond to C attach to CI

CH3

׀

CH3 – C – CI

׀

CH3

R

׀

R – C – CI

׀

R

Reactivity for Halogenoalkane

Class Functional Prefix Example

Halogenoalkane F, CI, Br, I - chloro chloroethane

Number carbon

IUPAC name Structure formula Molecular formula

1 chloromethane CH3CI CH3CI

2 chloroethane CH3CH2CI C2H5CI

3 chloropropane CH3CH2CH2CI C3H7CI

4 chlorobutane CH3(CH2)2CH2CI C4H9CI

chloromethane chloroethane chloropropane

Reactivity for halogenoalkane • Carbon bond to halogen – F, CI, Br, I • High electronegativity on halogen gp • High reactivity – due to polarity of C+- Br -

Nucleophile – Lone pair electron – Donate electron pair (Lewis base)

Chemical rxn Halogenoalkane

C - Br ᵟ+ ᵟ-

electron

Electron deficient

carbon

O–H ..

..

ᵟ- ᵟ+

C ᵟ+

Substitution rxn

CH3CH2CI + OH- → CH3CH2OH + CI-

H H

׀ ׀

H - C – C – CI

׀ ׀

H H

+ OH- ᵟ+ ᵟ-

H H

׀ ׀

H - C – C – OH + CI-

׀ ׀

H H

H Br H

׀ ׀ ׀

H - C – C – C – H

׀ ׀ ׀

H H H

CH3CHBrCH3 + OH- → CH3CHOHCH3 + Br-

+ OH-

H OH H

׀ ׀ ׀

H - C – C – C – H + Br-

׀ ׀ ׀

H H H

ᵟ+

ᵟ-

CH3 H

׀ ׀

CH3 – C – C – CI

׀ ׀

CH3 H

Electrophile - Electron deficient - Accept lone pair - Positive charge - Lewis Acid

C - Br

Reactivity for halogenoalkane • Carbon bond to halogen – F, CI, Br, I • High electronegativity on halogen gp • High reactivity – due to polarity of C+- CI -

C - Br ᵟ+ ᵟ-

electron

Electron deficient carbon

OH ..

ᵟ- ᵟ+

Nucleophilic Substitution rxn

CH3CH2CI + OH- → CH3CH2OH + CI-

H H

׀ ׀

H - C – C – CI

׀ ׀

H H

+ OH- ᵟ+ ᵟ-

H H

׀ ׀

H - C – C – OH + CI-

׀ ׀

H H

H Br H

׀ ׀ ׀

H - C – C – C – H

׀ ׀ ׀

H H H

CH3CHBrCH3 + OH- → CH3CHOHCH3 + Br-

+ OH-

H OH H

׀ ׀ ׀

H - C – C – C – H + Br-

׀ ׀ ׀

H H H

ᵟ+ ᵟ-

Nucleophile and Substitution Electrophile and Addition

vs Reactivity of Alkene - High reactivity - Unstable bond bet C = C - High reactivity – Weak pi bond overlap bet p orbital - Unsaturated hydrocarbon – ᴨ bond overlap

C = C Electron rich π electron

ᵟ- ᵟ-

H ᵟ+

C = C ᵟ- ᵟ-

E ᵟ+

E+ Electron deficient Nu

ᵟ-

ᵟ-

Nucleophile – Lone pair electron – Donate electron pair - Lewis Base

H H ׀ ׀

C = C

׀ ׀ H H

CH2=CH2 + Br2 → CH2BrCH2Br

+ Br – Br ᵟ- ᵟ+

H H ׀ ׀

H - C – C – H

׀ ׀ Br Br

vs

CH2=CH2 + HCI → CH3CH2CI

H H ׀ ׀

C = C

׀ ׀ H H

ᵟ- + H – CI

ᵟ+

H H ׀ ׀

H - C – C – H

׀ ׀ H CI

Electrophilic Addition rxn

Electrophile - Electron deficient - Accept lone pair - Positive charge - Lewis Acid

ᵟ-

Electron rich region

Electrophilic Substitution rxn

C6H6 + Br2 C6H5Br + HBr

+ Br-Br ᵟ+

+ NO2+

ᵟ+

Electrophile and Substitution Electrophile and Addition

vs

C = C Electron rich π electron

ᵟ- ᵟ-

ᵟ+

C = C ᵟ- ᵟ-

E ᵟ+

E+ Electron deficient

E ᵟ+

H H ׀ ׀

C = C

׀ ׀ H H

CH2=CH2 + Br2 → CH2BrCH2Br

+ Br – Br ᵟ- ᵟ+

H H ׀ ׀

H - C – C – H

׀ ׀ Br Br

vs

CH2=CH2 + HCI → CH3CH2CI

H H ׀ ׀

C = C

׀ ׀ H H

ᵟ- + H – CI ᵟ+

H H ׀ ׀

H - C – C – H

׀ ׀ H CI

Electrophilic Addition rxn

E

Electrophile - Electron deficient - Accept lone pair - Positive charge - Lewis Acid

ᵟ+ + H E

+ H

Electron rich region

H Br

+ HBr

C6H6 + HNO3 C6H5NO2 + HCI

AICI3 dry ether

warm/Conc H2SO4

H NO2

Reactivity of Alkene - High reactivity - Unstable bond bet C = C - High reactivity – Weak pi bond overlap bet p orbital - Unsaturated hydrocarbon – ᴨ bond overlap

Reactivity of Benzene (Unreactive) - Delocalization of electron in ring - Stability due to delocalized π electron - Substitution instead of Addition

ethene decolourize brown Br2(I)

benzene –stable (unreactive) toward addition rxn

H

C6H6 – no rxn with brown Br2(I)

Electrophile - Electron deficient - Accept lone pair - Positive charge - Lewis Acid

C - Br OH .. ᵟ- ᵟ+

Nucleophile Electrophile

ᵟ+

C = C ᵟ-

Nucleophile – Lone pair electron – Donate electron pair - Lewis Base

Organic Rxn

Addition rxn Substitution rxn

Nucleophilic Substitution

Free Radical Substitution

Electrophilic Substitution Electrophilic Addition rxn

Free radicle

CI CI

CI CI . .

:

Radical (unpair electron)

uv radiation

H H ׀ ׀

C = C

׀ ׀ H H

+ Br – Br

H H ׀ ׀

H - C – C – H

׀ ׀ Br Br

ᵟ+

ᵟ-

H H

׀ ׀

H - C – C – CI

׀ ׀

H H

+ OH-

H H

׀ ׀

H - C – C – OH + CI-

׀ ׀

H H

ᵟ- ᵟ+ H

E + + H

E ᵟ+

H H

׀ ׀

C = C

׀ ׀

H H

H H

׀ ׀

H - C – C – H

׀ ׀

CI CI

H H

׀ ׀

H - C – C – H

׀ ׀

H CI

H H

׀ ׀

H - C – C – H

׀ ׀

H OH

Add HCI

CI2 / UV

H H

׀ ׀

H - C – C – CI

׀ ׀

H H

H H

׀ ׀

H - C – C – OH + CI-

׀ ׀

H H

H H

׀ ׀

H - C – C – NH2 + CI-

׀ ׀

H H

H H

׀ ׀

H - C – C – CN + CI-

׀ ׀

H H

NH3

OH-

CN-

H

׀

H - C – H

׀

H

H

׀

H - C – CI + H

׀

H

CI2 → 2 CI•

CH3• + CI2 → CH3CI + CI•

CI• + CH4 → HCI + CH3•

H

Electrophile - Electron deficient - Accept lone pair - Positive charge - Lewis Acid

C - Br OH .. ᵟ- ᵟ+

Nucleophile Electrophile

H ᵟ+

C = C ᵟ-

Nucleophile – Lone pair electron – Donate electron pair - Lewis Base

Free radicle

CI CI

CI CI . .

:

Radical (unpair electron)

uv radiation

H H

׀ ׀

C = C

׀ ׀

H H

H H

׀ ׀

H - C – C – H

׀ ׀

CI CI

H H

׀ ׀

H - C – C – H

׀ ׀

H CI

H H

׀ ׀

H - C – C – H

׀ ׀

H OH

Add HCI

CI2 / UV

H H

׀ ׀

H - C – C – CI

׀ ׀

H H

H H

׀ ׀

H - C – C – OH + CI-

׀ ׀

H H

H H

׀ ׀

H - C – C – NH2 + CI-

׀ ׀

H H

H H

׀ ׀

H - C – C – CN + CI-

׀ ׀

H H

NH3

OH-

CN-

H

׀

H - C – H

׀

H

H

׀

H - C – CI + H

׀

H

CI2 → 2 CI•

CH3• + CI2 → CH3CI + CI•

CI• + CH4 → HCI + CH3•

Alkene – Addition rxn Halogenoalkane – Substitution rxn Alkane - Radical substitution

H OH

׀ ׀

H - C – C – H

׀ ׀

H H

H O

‖ ׀

H - C – C – H

׀

H

H O

‖ ׀

H - C – C – OH

׀

H

H O H

׀ ‖ ׀

H - C – C – C – H

׀ ׀

H H

H OH H

׀ ׀ ׀

H - C – C – C – H

׀ ׀ ׀

H H H

H OH H

׀ ׀ ׀

H - C – C – C – H

׀ ׀ ׀

H CH3 H

Alcohol – Oxidation rxn

10 alcohol 20 alcohol 30 alcohol

carboxylic acid aldehyde ketone

no reaction

׀ ׀ C- C –OH ׀ ׀

O ‖ C – C – C

O ‖ C – C – H

O ‖ C – C – OH

O ‖ C –C – C– O – C – C

O H ׀ ‖ C – C – N – C – C

No reaction

1o alcohol

[O]/Cr2O7/H+

Aldehyde

Ketone Carboxylic Acid

Free radical substitution

CI2/ UV

Halogenoalkane

Alkane

3o alcohol

[O]/ Cr2O7/H+

Substitution

warm / OH-

Alcohol

Substitution / CN-

Amine

Nitrile

Alcohol

Condensation

Amide

Amine

Carboxylic Acid

Alkene

Elimination

100C /Conc alcoholic OH-

Alkane Halogenoalkane Dihalogenoalkane

Condensation

Ester

Addition

Polymerisation

X

׀ ׀ C – C – CI ׀ ׀

׀ ׀ C = C ׀ ׀

׀ ׀ ׀ ׀ C – C – C – C ׀ ׀ ׀ ׀

׀ ׀ C – C ׀ ׀ H CI

׀ ׀ C – C ׀ ׀ CI CI

׀ ׀ C – C ׀ ׀ Br Br

׀ ׀ C – C ׀ ׀

׀ ׀ C – C – OH ׀ ׀

׀ ׀ C – C – CN ׀ ׀

׀ ׀ C – C – NH2 ׀ ׀ ׀ ׀ ׀

C – C – C –NH2 ׀ ׀ ׀

׀ ׀ C – C – COOH ׀ ׀

Start here

PolyAlkene

׀ ׀ C – C ׀ ׀ H H

H

׀

CH3 – C – Br

׀

H

CH3 H

׀ ׀

CH3 – C – C – Br

׀ ׀

CH3 H

Reactivity for halogenoalkane • Carbon bond to halogen – F, CI, Br, I • High electronegativity on halogen • High reactivity – polarity of C+- Br -

Nucleophile – Lone pair electron – Donate electron pair - (Lewis base)

Chemical rxn Halogenoalkane

C - Br ᵟ+ ᵟ-

electron

Electron deficient

carbon

O–H ..

.. ᵟ-

C ᵟ+

H H

׀ ׀

H - C – C – Br

׀ ׀

H H

+ OH- ᵟ+ ᵟ-

H H

׀ ׀

H - C – C – OH + Br-

׀ ׀

H H

Nucleophilic Substitution

Primary 10 - SN2

Primary 10 - SN2

- Experimentally rate expression = k [CH3CH2Br][OH-] - Rate dependent on conc- CH3CH2Br and OH-

- Molecularity = 2 - No bulky alkyl gp, less steric effect - Allow nucleophile to attack electron deficient carbon from opposite site (Inversion of configuration)

CH3CH2Br + OH- → CH3CH2OH + Br-

SN2 Substitution

Bimolecular collision bet 2 molecule

Nucleophilic

Bimolecular Nucleophilic Substitution

OH- + CH3CH2Br [ HO---CH2(CH3)---Br]- CH3CH2OH + Br-

HO-

Bond breaking and making in transition state

+ Br-

One step mechanism – Bond break and making in transition state

nucleophile attack

leaving gp

Click here to view SN2

slow step (RDS)

fast step

slow step (RDS) fast step

✓ 1ₒ SN2

Hydrolysis bromoethane (1o)

H

׀

OH- + CH3 – C – Br

׀

H

Bond Breaking and Making at transition state Br leaving gp substituted with OH-

H H

׀ ׀ CH3 - C – Br + OH- CH3 – C – OH + Br - ׀ ׀ H H

Nucleophile collide with bromoethane

CH3CH2Br + OH- → CH3CH2OH + Br- Single step

Nucleophilic Substitution

Click here view SN2

SN2 Substitution

Nucleophilic

Bimolecular Nucleophilic Substitution

Bimolecular collision bet 2 molecule

- Experimentally rate expression = k [CH3CH2Br][OH-] - Rate dependent on conc = CH3CH2Br and OH-

- Molecularity = 2 - No bulky alkyl gp, less steric effect - Allow nucleophile to attack electron deficient carbon from the opposite site (Inversion of configuration)

Formation of ethanol

1 step mechanism (concerted)

SN2 1ₒ

Nucleophile – Lone pair electron – Donate electron pair - (Lewis base)

CH3

׀

CH3 – C – Br

׀

CH3

CH3

׀

CH3 – C – Br

׀

CH3

R

׀

R – C – Br

׀

R

Reactivity for halogenoalkane • Carbon bond to halogen gp – F, CI, Br, I • High electronegativity on halogen gp • High reactivity – polarity of C+- Br -

Chemical rxn Halogenoalkane

C - Br ᵟ+ ᵟ-

electron

Electron deficient

carbon

O–H ..

.. ᵟ-

C ᵟ+

+ OH- ᵟ+ ᵟ-

Nucleophilic Substitution

Tertiary 30 – SN1

Tertiary 30 – SN1

- Experimentally rate expression = k [(CH3)3CBr] - Rate dependent on conc - (CH3)3CBr

- Molecularity = 1 - 3 Bulky alkyl gp, Steric hindrance effect - 30 carbocation more stable due to inductive effect • 3 alkyl gp stabilize carbocation by inductive effect push electron to carbocation (reducing positive charge) making it more stable

SN1 Substitution

Unimolecular (1 molecule)

Nucleophilic

Unimolecular Nucleophilic Substitution

+ :OH-

carbocation (Intermediate)

+ Br-

1st step mechanism – carbocation formation

nucleophile attack

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(CH3)3CBr + OH- → (CH3)3COH + Br-

CH3

׀

CH3 – C – OH + Br -

׀

CH3

slow step (RDS)

heterolytic fission Br leaving gp

fast step

2nd step mechanism – OH attack carbocation

(CH3)3CBr → (CH3)3C+ + Br- 1st step (slow)

(CH3)3C+ + OH- → (CH3)3COH 2nd step (fast)

✓ 3ₒ SN1

Formation of 2 methylpropan-2-ol

Hydrolysis 2-bromo- 2- methylpropane (3o)

CH3 │

CH3 - C – Br

│

CH3

Carbocation formation (Intermediate) Nucleophile OH- attack carbocation

Heterolytic fission - Carbocation and Br- form

(CH3)3CBr → (CH3)3C+ + Br- 1st step (slow)

(CH3)3C+ + OH- → (CH3)3COH 2nd step (fast)

CH3 CH3

׀ ׀ CH3 - C – Br + OH- CH3 –C – OH + Br - ׀ ׀ CH3 CH3

Nucleophilic Substitution

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- 3 Bulky alkyl gp - Steric hindrance effect - 30 carbocation more stable due to inductive effect • 3 alkyl gp stabilize carbocation by inductive effect push electron to carbocation (reducing positive charge) making it more stable

SN1 Unimolecular (1 molecule)

Substitution

Nucleophilic

Unimolecular Nucleophilic Substitution

2 step mechanism

3ₒ SN1

H Br H

׀ ׀ ׀

H - C – C – C – H

׀׀ ׀ ׀ ׀

H H H

+ :OH- ᵟ+

Nucleophilic Substitution

Secondary 20 - SN1 and SN2

- Experimentally rate expression = k [CH3CHBrCH3][OH-] - Rate dependent conc = CH3CHBrCH3 and OH-

- Molecularity = 2 - No bulky alkyl gp, less steric effect - Allow nucleophile to attack electron deficient carbon from opposite site (Inversion of configuration)

SN2 Substitution

Bimolecular collision bet 2 molecule

Nucleophilic

Bimolecular Nucleophilic Substitution

HO-

Bond breaking and making in transition state

+ Br-

One step mechanism – Bond break and making in transition state

nucleophile attack

leaving gp

slow step (RDS)

fast step

CH3CHBrCH3 + OH- → CH3CH(OH)CH3 + Br-

H OH H

׀ ׀ ׀

H - C – C – C – H + Br -

׀ ׀ ׀

H H H

CH3 CH3 CH3

SN1 Substitution

Nucleophilic

Unimolecular (1 molecule)

Unimolecular Nucleophilic Substitution

heterolytic fission Br leaving gp

slow step (RDS)

carbocation (Intermediate)

+ Br-

nucleophile attack

+ :OH-

CH3

1st step mechanism – carbocation formation

fast step

+

+

2nd step mechanism – OH attack carbocation

CH3

Click here SN1 vs SN2

1 step mechanism (concerted)

CH3CHBrCH3 → CH3CH+ CH3 + Br- 1st step (slow)

CH3CH+ CH3 + OH- → CH3CHOHCH3 2nd step (fast)

2 step mechanism CH3CHBrCH3 + OH- → CH3CH(OH)CH3 + Br-

Click here SN1 vs SN2 Khan academy

✓

2ₒ SN1 SN2

Electrophile - Electron deficient - Accept lone pair - Positive charge - Lewis Acid

C - Br OH .. ᵟ- ᵟ+

Nucleophile Electrophile

H ᵟ+

C = C ᵟ-

Nucleophile – Lone pair electron – Donate electron pair - Lewis Base

Free radicle

CI CI

CI CI . .

:

Radical (unpair electron)

uv radiation

H+ Br+ NO2+ :OH- :CN- H2O: :NH3

Homolytic fission Heterolytic fission

CI CI : uv radiation

CI CI . . fish hook arrow Single electron movement

A B :

A B :

A – B A + :B

Double headed arrow pair electron movement

Control by electronic factor (charges)

vs vs

vs

Nucleophilic Substitution

Primary 10 - SN2 Secondary 20 -SN1 and SN2 Tertiary 30 – SN1

SN1

SN2

Control by steric factor (alkyl gp)

SN2 SN1

Favour 10 30

Nature mechanism

1 step (transition state)

2 step (carbocation)

Rate lower higher

Solvent Polar aprotic Polar protic

Reaction profile

Click here SN1 vs SN2

Factor affecting Rate of Nucleophilic Substitution

• Bond polarity decrease ↓ • Bond strength decrease ↓

• Rate fastest (Halogen leave easily) Iodo > Bromo > Chloro > Fluoro

Nucleophilic Substitution

• SN 1 > SN 2 mechanism • 3o > 2o > 1o

• 3o – SN 1 - Carbocation - faster • 1o - SN 2 – Transition state - slower

Nature of solvent

Nature of Halogen

CH3

׀

CH3 – C – Br

׀

CH3

H

׀

CH3 – C – Br

׀

CH3

H

׀

CH3 – C – Br

׀

H

> > CH3CH2 – I > CH3CH2 – CI > CH3CH2 – F

fastest slowest

weak bond strong bond

C - Br OH Nucleophile

ᵟ-

H bond to O or N H2 bonding/donate H+

H2O, NH3 CH3OH, CH3CH2OH Able to solvate cation and anion

Polar protic Polar aprotic

Lack acidic H, no H2 Bonding Acetone/CH3COCH3, DMSO, CH3CN

Solvate cation–nucleophile free for SN2

H H

׀ ׀

H - C – C – OH

׀ ׀

H H

H

׀

H -– C – OH

׀

H

ᵟ+

Nature of Halogenoalkane

SN1

polar + H2 bonding

:O:

‖

CH3 – C – CH3

:O:

‖

CH3 – S – CH3

polar only

SN2

Rate of hydrolysis of halogenoalkane

C4H9CI + H2O → C4H9OH + H+ + CI-

C4H9Br + H2O → C4H9OH + H+ + Br-

C4H9I + H2O → C4H9OH + H+ + I-

Reaction Time ppt to appear Observation

1-chlorobutane slowest white ppt 1-bromobutane cream ppt

1-iodobutane fastest yellow ppt

Method:

- Prepare 3 test tube contain 2 ml of ethanol each

- Pipette 0.1ml of chloro, bromo and iodobutane to each test tube

- Leave 3 test tube in 60C bath.

- Add 1ml AgNO3, mix and record time ppt to form

Ag+ react CI- → AgCI (white ppt) Ag+ react Br- → AgBr (cream ppt) Ag+ react I- → AgI (yellow ppt)

fastest slowest

1-iodobutane 1-chlorobutane ✓

+ Ag+

Factor affecting Rate of Nucleophilic Substitution

Click here protic/aprotic solvent

Nucleophilic Substitution

Nature of solvent

H bond to O or N H2 bonding/donate H+

H2O, NH3 CH3OH, CH3CH2OH Able to solvate cation and anion

+ Br-

Polar protic Polar aprotic

Lack acidic H, no H2 Bonding Acetone/CH3COCH3, DMSO

Solvate cation–nucleophile free for SN2

NaOH → Na+ + OH-

SN1 SN2

H2O solvate carbocation and Br- form Stabilize it – exist in intermediate state

H H

׀ ׀

H - C – C – Br

׀ ׀

H H

+ OH-

H H

׀ ׀

H - C – C – OH + Br-

׀ ׀

H H

H H

׀ ׀

H - C – C – OH

׀ ׀

H H

CH3 │

CH3 - C – Br

│

CH3

carbocation solvated by H2O

anion solvated by H2O

H

׀

H -– C – OH

׀

H

Acetone solvate cation – nucleophile free for SN2 No H2 bond- unable to solvate anion/nucleophile

:O:

‖

CH3 – C – CH3

: O

:

‖

CH

3 –

C –

CH

3

Na+ solvated by CH3COCH3

nucleophile free to attack

C - Br OH Nucleophile

ᵟ+ ᵟ-

Click here protic/aprotic solvent

:O:

‖

CH3 – C – CH3

:O:

‖

CH3 – S – CH3

Click here expt protic/aprotic solvent