IB Chemistry on Electrophilic Addition and Synthetic routes

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Transcript of IB Chemistry on Electrophilic Addition and Synthetic routes

  • 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 + -

    electron

    Electron deficient carbon

    OH ..

    - +

    Nucleophilic Substitution rxn

    CH3CH2CI + OH- CH3CH2OH + CI

    -

    H H

    H - C C CI

    H H

    + OH- + -

    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

    + -

    Nucleophilic Substitution Electrophilic Addition

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

    C = C Electron rich electron

    - -

    H +

    C = C - -

    E +

    E+ Electron deficient Nu

    -

    -

    Nucleophile Lone pair electron Donate electron pair - Lewis Base

    H H

    C = C

    H H

    CH2=CH2 + Br2 CH2BrCH2Br

    + Br Br - +

    H H

    H - C C H

    Br Br

    vs

    CH2=CH2 + HCI CH3CH2CI

    H H

    C = C

    H H

    - + H CI

    +

    H H

    H - C C H

    H CI

    Electrophilic Addition rxn

  • -

    Electron rich region

    Electrophilic Substitution rxn

    C6H6 + Br2 C6H5Br + HBr

    + Br-Br +

    + NO2+

    +

    Electrophilic Substitution

    vs

    C = C Electron rich electron

    - -

    +

    C = C - -

    E +

    E+ Electron deficient

    E +

    H H

    C = C

    H H

    CH2=CH2 + Br2 CH2BrCH2Br

    + Br Br - +

    H H

    H - C C H

    Br Br

    vs

    CH2=CH2 + HCI CH3CH2CI

    H H

    C = C

    H H

    - + H CI +

    H H

    H - C C H

    H CI

    Electrophilic Addition rxn

    E

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

    + + 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 bond overlap

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

    C6H6 no reaction with brown Br2(I)

    ethene decolourize brown Br2(I)

    Benzene stable (unreactive) toward addition rxn

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

    H

    Electrophilic Addition

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

    C - Br OH .. - +

    Nucleophile Electrophile

    +

    C = C -

    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

    +

    -

    H H

    H - C C CI

    H H

    + OH-

    H H

    H - C C OH + CI-

    H H

    - + H

    E + + H

    E +

    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 .. - +

    Nucleophile Electrophile

    H +

    C = C -

    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

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

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

    C = C Electron rich electron

    - - Br +

    H H

    C = C

    H H

    + H Br - +

    H H

    H - C C H

    + H

    Electrophilic Addition

    Symmetrical Alkene

    HBr polar

    CH2=CH2 + HBr CH3CH2Br

    : Br-

    H H

    H - C C H

    H Br

    CH2=CH2 + Br2 CH2BrCH2Br

    Electrophilic addition to symmetrical alkene

    H H

    C = C

    H H

    + Br Br + -

    Br2 non polar : induced dipole due to C=C

    H H

    H - C C H

    + Br

    : Br-

    H H

    H - C C H

    Br Br

    carbocation

    carbocation

    Heterolytic fission

    Heterolytic fission

    CH2=CH2 + Br2/H2O CH2BrCH2Br

    H H

    C = C

    H H

    + Br Br

    Heterolytic fission

    + -

    H H

    H - C C H

    + Br

    : Br-

    H H

    H - C C H

    Br Br

    H H

    H - C C H

    + Br

    : OH- from

    H2O

    H H

    H - C C H

    Br OH

    H H

    C = C

    H H

    H H

    CH3 C = C CH3

    + H Br

    H H

    H - C C H

    H Br

    + H Br

    H