SL Reaction pathways
• Deduce reaction pathway given the starting
materials and the product, e.g:
K Cr O
CH3CH2OH
CH3CH2CHO
• Conversions with more than two stages will
not be assessed. Reagents, conditions and
equations should be included
• The compound and reaction types in this topic
are summarized in the schemes on the next
slides
2
2 7
propanoic acid
oxidation
polypropene
propanal
oxidation
(M) polyaddition
1-propanol
propene
addition
addition
+H2
+HCl
(M) substitution
+OH-
1-chloro-propane
(M) substitution via radical reaction
1,2-dichloropropane
(M) substitution via radical reaction
propane
(M) further radical substitution to tri- and tetra-chloropropane
propanoic acid
Oxidation of primary alcohol with acidified K2Cr2O7.
Reflux to get the product
polypropene
Poly-addition. Radical mechanism.
Initiation, prolongation and termination
propanal
Oxidation of primary alcohol with acidified
K2Cr2O7. Distillation to get the product
1-propanol
propene
Addition reaction.
H2 and Ni-catalyst
1,2-dichloropropane
Addition reaction.
Hydrogen halide (HCl),
spontaneous at STP
(M) substitution reaction with NaOH;
SN1 or SN2
1-chloro-propane
(M) substitution via radical mechanism.
Induced by homolytic cleavage of Cl2
by UV-light
(M) substitution via radical mechanism.
Induced by homolytic cleavage of Cl2
by UV-light
propane
(M) further radical substitution to tri- and tetra-chloropropane
H H O
H
H C C CO
H
C
polyalkene
C
H
carboxylic acid
H H
H
CH3
oxidation
O
H
H
n
C
C
H
C
H
H
H
aldehyde
(M) polyaddition
oxidation
H
H
C
C
C
H
H
H
H
alkene
H
H
H
H
C
C
C
H
H
H
primary alcohol
OH
(M) substitution
+OH-
addition
addition +HCl
H
+Cl2
chloroalkane
H
H
H
C
C
C
H
H
H
Cl
H
H
C
l
C
C
l
C
C
H
(M) substitution via radical reaction
(M) substitution via radical reaction
H
H
H
dichloroalkane
H
(M) further radical substitution to tri- and tetra-chloropropane
H
H
H
C
C
C
H
H
H
H
alkane
What is formed?
oxidation
oxidation
(M) polyaddition
addition
addition
+H2
+HCl
(M) substitution
+OH-
1-chloro-butane
(M) substitution via radical reaction
(M) substitution via radical reaction
butane
(M) further radical substitution to tri- and tetra-chloropropane
propanone
polypropene
oxidation
(M) polyaddition
2-propanol
1-propene
addition
(M) substitution
+HCl
addition
+H2
+OH-
2-chloro-propane
1,2-dichloropropane
(M) substitution via radical
reaction
(M) substitution via radical reaction
(M) further radical substitution
to tri- and tetra- chloropropane
propane
propanone
Oxidation of secondary alcohol with acidified
K2Cr2O7
polypropene
2-propanol
(M) polyaddition
(M) substitution +OH-
1-propene
addition
addition
2-chloro-propane
+HCl
+Cl2
(M) substitution via radical reaction
1,2-dichloropropane
(M) substitution via radical
reaction
propane
(M) further radical substitution to tri- and tetra chloropropane
H
H
polyalkene
C
C
H
CH3
H
H
O
H
C
C
C
ketone
H
H
H
n
oxidation
(M) polyaddition
H
H
H
C
C
C
H
H
H
H
alkene
H
O H
H
C
C
C
H
H
H
addition
+HCl
addition
+H2
secondary
alcohol
H
(M) substitution +OHH
H
C
l
secondary
C
H
C
C
H
chloroalkane
H
H
H
(M) substitution via radical
reaction
H
H
C
l
C
C
l
C
C
H
H
H
H
(M) substitution via radical reaction
dichloroalkane
H
(M) further radical substitution to tri- and tetra chloropropane
H
H
H
C
C
C
H
H
H
H
alkane
What is formed?
oxidation
substitution
+OH-
2-chloro-butane
substitution via radical
reaction
butane
Draw structural formula of reactants and products, name them
and give reaction pathway
K2Cr2O7
CH3CH2CHO
H2
CH3CH=CHCH3
CH3Br
CH3CH3
NaOH
K2Cr2O7
UV-light, Cl2
CH3CH=CHCH2CH3
HI
Answers
K2Cr2O7
CH3CH2CHO
CH3CH2COOH
propanal
propanoic acid
H2
CH3CH=CHCH3
butane
NaOH
methylbromide
CH3CH3
addition
CH3CH2CH2CH3
2-butene
CH3Br
oxidation
UV-light, Cl2
ethane
CH3CH=CHCH2CH3
2-pentene
K2Cr2O7
CH3OH
methanol
substitution
CH2O
methanal
radical substitution
CH2ClCH3
chloroethane
HI
CH3CHICH2CH2CH3
2-iodopentane
addition
oxidation
1-3. Substitution via radical mechanism. Induced by homolytic cleavage of Cl2
by UV-light.
4. Addition reaction. Hydrogen halide, spontaneous at STP
5. Addition reaction. H2 and Ni-catalyst
6. Addition reaction. Halogene, spontaneous at STP
7. Poly-addition. Radical mechanism. Initiation, prolongation and termination
8. Substitution reaction with NaOH; SN1 or SN2
9. Oxidation of primary alcohol with acidified K2Cr2O7. Distillation to get the
product
10. Oxidation of primary alcohol with acidified K2Cr2O7. Reflux to get the
product
11. Oxidation of secondary alcohol with acidified K2Cr2O7
HL Reaction pathways
(M) Substitution reaction. SN1 or SN2
CN-
1-chloro-propane
propene
(M) Elimination reaction.
Hot, concentrated and reflux
1-propanol
butanenitrile
Reduction with H2
and Ni-catalyst
(M) Substitution reaction.
SN1 or SN2
NH3
propylamine,
butylamine
Condensation reaction.
Acid catalyst (or alkaline catalyst,
but more common when hydrolysis of ester).
Equilibrium reaction.
propanoic acid
1-propyl
propanoate
Condensation reaction.
Acid catalyst (or alkaline
catalyst).
Equilibrium reaction.
propyl amide
HL Reaction pathways
alkene
H
H
(M) Elimination
H
H
C
C
C
H
H
H
(M) Substitution
CN-
H
C
C
C
H
H
H
H
H
H
H
H
C
C
H
H
H
C
H
Cl
H
H
nitrile
H
C
C
C
H
H
H
(M) Substitution
OH
H
H
Condensation
N
Reduction
chloropropane
alcohol
C
H
H
H
C
C
C
H
H
H
H
NH2
H
H
H
H
C
C
C
C
H
H
H
H
NH 2
amine
carboxylic acid
Condensation
H H O
H
H C C CO
ester
HH O
H H
amide
O
H
HH H H
H
H
H
C
C
C
C
N
C
HC C CO C C C
H
H
C
H
HH
H
H
H
H
HH H H
H
What is formed?
substitution CN-
1-chloro-butane
elimination
reduction H2
substitution NH3
1-butanol
Condensation reaction.
Acid catalyst (or alkaline catalyst,
but more common when hydrolysis of ester).
Equilibrium reaction.
butanoic acid
Condensation reaction.
Acid catalyst (or alkaline
catalyst).
Equilibrium reaction.
HL Reaction pathways
alkene
6
1. Elimination reaction. Hot, concentrated and reflux
2. Substitution reaction. SN1 or SN2
3. Substitution reaction. SN1 or SN2. (Can be substituted up 4 times to a
quarternary ammonum salt)
4. Condensation reaction. Acid catalyst (or alkaline catalyst, but more common
when hydrolysis of ester). Equilibrium reaction.
5. Condensation reaction. Acid catalyst (or alkaline catalyst). Equilibrium
reaction.
6. Nitrile to amin: Reduction with H2 and Ni-catalyst