C H 3 C H H Br C H 3 C H H OH - HO: + :Br - δ + δ - C H 3 C H H CN C H 3 C H H Br - NC: + :Br - δ + δ - :OH - C C H H CH 3 Br H H C C H CH 3 H H + Br - + H 2 O C C H H H H C C H H Br Br H H C + C Br H H H H Br Br δ + δ - :Br - C + C H CH3 H H C H3 C C H CH 3 H H C H 3 Br C C CH 3 H H C H 3 δ + δ - :Br - H Br H OSO 2 OH C C H H H C H 3 δ + δ - - :OSO 2 OH C + C H H H C H3 H C C H H H C H 3 H OSO 2 OH STEP ONE Initiation Br 2 2Br . Essential condition: UV light CH 3 CH 3 + Br . HBr + CH 3 CH 2 . STEP TWO Propagation CH 3 CH 2 . + Br 2 CH 3 CH 2 Br + Br . STEP THREE Termination CH 3 CH 2 . + Br . CH 3 CH 2 Br CH 3 CH 2 . + CH 3 CH 2 . CH 3 CH 2 CH 2 CH 3 Mechanism Summary for A-level AQA Chemistry Nucleophilic Substitution of Halogenoalkanes with aqueous hydroxide ions. Nucleophilic Substitution of Halogenoalkanes with cyanide ions. Elimination of Halogenoalkanes with ethanolic hydroxide ions Electrophilic Addition of Alkenes with Bromine Electrophilic Addition of Alkenes with hydrogen bromide Electrophilic Addition of Alkenes with sulphuric acid Free Radical Substitution of Alkanes with Bromine : C H 3 C CH 3 O H H C H 3 C CH 3 O + H H H C C + CH 3 H H H H H + H + C C CH 3 H H H Acid catalysed elimination mechanism: alcohols alkenes The H + comes from the conc H 2 SO 4 or conc H 3 PO 4 C C H H H H C C + H H H H H O H H C C O + H H H H H H H C C O H H H H H H H + H + Acid catalysed addition mechanism for hydration of ethene The H + comes from the conc H 3 PO 4 Dr.Ashar Rana www.chemistryonlinetuition.com [email protected]
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Mechanism Summary for A-level AQA Chemistry...Mechanism Summary for A-level AQA Chemistry Nucleophilic Substitution of Halogenoalkanes with aqueous hydroxide ions. Nucleophilic Substitution
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Transcript
CH3 C
H
H
Br CH3 C
H
H
OH-HO:
+ :Br -δ+ δ-
CH3 C
H
H
CNCH3 C
H
H
Br-NC:
+ :Br -δ+ δ-
:OH-
C C
H
H
CH3
Br
H
H C C
H
CH3
H
H
+ Br - + H2O
C C
H
H
H
H
C C
H
H
Br Br
H
H
C+
C
Br
H
HH
H
Br
Brδ+
δ-
:Br -
C+
C
H
CH3
HH
CH3
C C
H
CH3
HH
CH3
Br
C C CH3
HH
CH3
δ+
δ- :Br -
H
Br
H
OSO2OH
C C H
HH
CH3
δ+
δ-
-:OSO2OH
C+
C H
HH
CH3
H
C C H
HH
CH3
HOSO2OH
STEP ONE Initiation
Br2 2Br .Essential condition: UV light
CH3CH3 + Br. HBr + CH3CH2.
STEP TWO Propagation
CH3CH2. + Br2 CH3CH2Br + Br.
STEP THREE TerminationCH3CH2
. + Br. CH3CH2Br
CH3CH2. + CH3CH2
. CH3CH2CH2CH3
Mechanism Summary for A-level AQA Chemistry
Nucleophilic Substitution ofHalogenoalkanes with aqueous hydroxideions.
Nucleophilic Substitution of Halogenoalkaneswith cyanide ions.
Elimination of Halogenoalkanes with ethanolichydroxide ions
Electrophilic Addition of Alkenes with Bromine Electrophilic Addition of Alkenes with hydrogenbromide
Electrophilic Addition of Alkenes with sulphuric acid