Slide 1 - Papanui High School

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Describe the structural
formulae and reactions of
compounds containing
selected functional groups
4 credits
Selected organic functional groups are limited to:
• Haloalkane
• Alcohol
• Alkene
• Alkyne
• Ester
• Carboxylic acid
Compounds are limited to:
Those containing no more than 8 carbons.
Larger organic molecules may be used in Qs
linking structure & reactivity.
Naming
compounds
Structural and
geometric
isomers
Knowledge of
primary,
secondary &
tertiary
alcohols &
haloalkanes
polymerisation
Organic Chemistry
Reactions of
alkenes
H2/Pt
Br2
Distinguishing
tests
Cl2
MnO4H2O/H+ & HCl
identify major
& minor
products
Acid reactions
of carboxylic
acid
Halogenation
of alkanes
Elimination of
water from
alcohol
Oxidation of
primary
alcohols to
carboxylic acid
Formation &
hydrolysis of esters
e.g. triglycerides
Fats, oils and soaps
•Triglyceride is a fat that contains 3 ester links
•Made from 3, long-chain carboxylic acids +
glycerol (triol)
•In the esterfication reaction, 3H20 is formed
(OH from acid + H from glycerol)
Beware;
they can
change the
orientation
Divide between
C and O, add
Hs to form
triol and OHs
to form acid
Fats, oils and soaps
Like all esters, triglycerides undergo hydrolysis.
This reaction can be catalysed by either acid or
base.
1.With acid
An acid catalyst is used (not conc. acid) to form
glycerol (triol) and carboxylic acid again:
2.With alkali (OH-)
If NaOH is used, it reacts with the carboxylic
acid to form a sodium salt and glycerol. The
sodium salt in this case is called ‘soap’ and the
reaction is called ‘saponification’
Acid conditions: glycerol and palmitic acid formed.
Alkali conditions: glycerol and the sodium salt of palmitic
acid formed
Notice
there are 3
diff. acids
In basic conditions: glycerol would still form but instead of
the acid a sodium salt would form.
Na
Polymerisation
•A polymer is a large molecule made of small
molecules called monomers
•In addition polymerisation, nothing else is made
•All monomers are alkenes
•Could be asked to draw monomers from polymers
or vice versa
Isolate 2 OH
carbons
to form the
basis
CH=CH
2
of the alkene
monomer
Break the double
bond, attach to
next monomer
Isolate 2 carbons,
straighten them
and put the double
bond in
Naming compounds
Learn functional groups and endings!
Group
Alkane
Alkene
Alkyne
Alcohol
Haloalkane
Carboxylic
acid
Ester
Structure
C-C
C=C
C=C
-OH
e.g. –Cl
OH
C=O
-C=O
O
Name ending
-ane
-ene
-yne
-anol
e.g Chloro-ane
-anoic acid
-thyl-anoate
Crocodiles! What
is eaten first is
named first!
1-chloropropane
methylpropanoate
Numbering
begins at ene
end
-anoic grp is
always on
carbon 1
Structural isomers
Same number of atoms in a different
arrangement
Geometric isomers
• Different arrangements of atoms in space
• Cis (same side) & trans (across)
• Due to double bond being unable to rotate
• Can have different properties e.g. polarity &
boiling point
Don’t need to give
number placing for
methyl and ene. They
can be nowhere else!
methylpropene
cyclobutane
But-1-ene
Cannot form cis &
trans because the
groups on each C
are not different
Base the drawing
around the double bond
to examine the groups
But-2-ene
Can form cis & trans because the
groups on each C are different and
the double bond doesn’t allow
rotation
Remember this! It’s the
stock answer for
explaining geometric
isomers
Reactions of alkenes
All types of
addition reactions
Reaction type
Reagent
Hydrogenation Hydrogen
Watch out for
Markovnikov’s!
Asymmetrical
Conditions
Product
alkene = 2 products
Hydration
Water
Pt/H2 or
Ni/H2
H+/H20
Halogenation
Halogen
Br2 or Cl2 Haloalkane
Halogenation
Hydrogen
HCl or
Haloalkane
halide
HBr
Potassium
H+/MnO4- Diol
Watch out for
permanganate
Oxidation
Markovnikov’s!
Asymmetrical
alkene = 2 products
Alkane
Alcohol
Primary, secondary & tertiary
• Classifications in alcohols and haloalkanes
• Look at the Carbon the alcohol/halogen is
attached to. Is this attached to 1, 2 or 3
carbons?
• Form straight line (!), T-shape or cross
primary
secondary
primary
tertiary
Reactions of alcohols
• Elimination of water (dehydration):
Conc. H2SO4
alcohol

Alkene + water
• Oxidation of 1° alcohol:
H+/Cr2O72-
1° alcohol  (aldehyde)  Carboxylic acid
Dichromate turns from orange
to green
Can use H+/MnO4- as oxidising agent instead. Purple to colourless
• Esterfication:
Conc. H2SO4
alcohol + Carboxylic acid  ester
This is a
dehydration
reaction
(elimination)
Alcohol + acid…
Oxidation of a
primary alcohol…
Potassium permanganate will turn from purple
to colourless
Reactions of carboxylic acids
• Normal acid reaction e.g. fizzing with metal 
H2 & fizzing with carbonates  CO2 & litmus
turning red
• Form metal salts involving the organic acid e.g.
sodium methanoate
• Form esters when reacted with alcohols
Distinguishing tests
Group
H+/Cr2O72-
Sodium
Smell
carbonate
sol.
Warm
H+/MnO4-
Alcohol
1° turns
from
orange to
green
Forms 1
layer
1° turns Stays
from
orange
purple to
colourless
Haloalkane
Stays
orange
Forms 2
layer
Stays
purple
Stays
orange
Stays
orange
pungent Stays
Forms 1
layer that
purple
fizzes
Stays
orange
Ester
Stays
orange
Forms 2
layers
Stays
purple
Stays
orange
Alkane
Stays
orange
Forms 2
layers
Stays
purple
Slowly
decolour
w/ uV
Alkene
Stays
orange
Forms 2
layers
Carbox.
Acid
Damp
litmus
Turns
red
fruity
strong
Bromine
water
Purple to Quickly
colourless decolour
Acidified potassium dichromate
(H+/Cr2O72-)
Propan-1-ol will turn acidified potassium dichromate from
orange to green. Propanoic acid will remain orange.
There are other
possible answers,
see how many you
can come up with!
hexane
Decolourises bromine slowly
with UV light
Saturated so undergoes a
substitution reaction
Forms 1-bromohexane
hex-1-ene
Decolourises bromine
quickly
unsaturated so undergoes an
addition reaction
Forms 1,2-dibromohexane
CH3CH2CH2CH2CH2CH3 + Br2
CH2CHCH2CH2CH2CH3 + Br2
CH2BrCH2CH2CH2CH2CH3 + HBr
CH2BrCBrCH2CH2CH2CH3 + HBr
So B must be a
primary alcohol
and reagent D
must be an
oxidant
Propan-2-ol
End
product =
ester. Reagent
= alcohol.
So C
To form
a
sodium saltmust
of be…
an ester…
NaOH
Adding water to
an asymmetric
alkene…but which
product goes
where?
Propan-1-ol
H+/Cr2O72-
Propanoic acid
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