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Organic 2:
Carboxylic acid
derivatives and
polymers
Carboxylic acids
Remember Yr11 patterns?!:
metal + acid  salt + hydrogen
MASH
base + acid  salt + water
BASH O
CASH OCO carbonate + acid  salt + water + carbon dioxide
2
2
2
For weak acids, the metal in each case
attaches to the COO- group to form the salt
Reactions:
• Making esters with alcohol
• Making acyl chloride
• acid + PCl5 or PCl3 or SOCl2 → acyl cloride + HCl + rest
(nucleophilic substitution)
• Lucas will not work (can disting. COOH & OH)
Carboxylic acids
Explain why an acid turns damp litmus red:
-COOH + H2O → -COO- + H3O+
Not really the right place but...
Explain why an amine turns damp litmus blue:
-NH2 + H2O → -NH3+ + OH-
Acyl chlorides
HCl is produced in every reaction!
• Acyl chloride + H2O → Carboxylic acid + HCl
• Nucleophilic substitution
• Acyl chloride + alcohol → ester + HCl
• Condensation
• Doesn’t require heat/catalyst so preferred
method for making ester
• Remember crocodile is an alcoholic!!!!
• Acyl chloride + NH3(alc) → 1 amide + HCl
• Nucleophilic substitution
• HCl will further react with NH3 to form NH4Cl
• Acyl chloride + amine → 2 amide + HCl
• Nucleophilic substitution
Esters
• Carboxylic acid + alcohol → Ester + H2O
• Slow. Requires reflux/catalyst conc. H2SO4
• Distillation separates products. Esters come off
first
• Formation of triglycerides:
• Glycerol (alcohol) + fatty acids (long chain
carboxylic acids)
•
•
•
•
Hydrolysis of esters: Using water to split them
needs weak acid (forms alcohol + carbox acid)
or weak alkali (acid product reacts to form salt)
this is how soap is formed
Amides
• Neutral. Do not react with acids to form salts
(different to amines)
• Acyl chloride + NH3(alc) → amide + HCl
• Ester + NH3(alc) → amide + alcohol
(Slow)
• Hydrolysis of amides. Heating with mineral acid
or alkali
• Amide + H3O+ → Carboxylic acid + NH4+
• Amide + OH- → -COO- + NH3
• Popular with examiners
Polymers
From Yr12: addition polymers
• monomers containing a double bond form a long
chain containing single bonds
• e.g. Polyethene, PVC, polypropylene, polystyrene
Condensation polymers: H2O or HCl is lost at each join
Polyesters
• reacting diol with
dicarboxylic acid
• Could have one
monomer containing
both groups
• e.g. Terylene
• HOCH2CH2OH +
HOOC-C6H6-COOH
Polyamides
• reacting diamine with
dicarboxylic acid or
acyl chloride
• e.g. Nylon
• hydrolysed by dilute
acid into carboxylic
acid + amine
HOOC-
-COOH HO-
-OH HOOC-
-COOH HO-
-OH
HOOC-
+H2O
+H2O
+H2O
-COO-
-OOC-
-COO-
Look for the ester link
(COO). To write the
monomers from the polymer,
split the Os and add H to
the O and OH to CO
-OH
HOOC-
-COOH H2N-
-NH2HOOC-
-COOH H2N- -NH2
HOOC-
+H2O
-COHN-
+H2O
+H2O
-NH OC-
-COHN-
Look for the amide
O
link (CNH). To write the
monomers from the polymer,
split between the O and H,
adding OH to the O and H to
the NH
-NH2
Natural Polymers
Protein
• Amino acids
contain a
carboxylic acid
group and an
amine group
• Condensation
• forms amide
links known as
peptide links
H
HOOC-C-NH2
R
Carbohydrate
• Glucose
(C6H12O6)
molecules join to
form starch
• neighbouring
OH meet to
expel H2O
Look for the CONH link
OH
ONa
2
OH
ONa
2
ONa
ONa
In acid conditions, the COOH group
would remain
and
tothe
CO NH
group
-OH
2 would
InAdd
OH
, Hthe
COOH
will
react become
Add
to
NH
groups
NH3+
to form salt...
Define
word
Using‘polymer’
generic using
structures,
Define
‘polyester’
giving
lots
‘monomer
write monomers
of detail and their
polymermade from the joining of
A polymer is a long chain molecule
repeating units called monomers.
A polyester is formed from the joining of monomers
containing an alcohol group and a carboxylic acid via
condensation to form an ester link ejecting a molecule of
water or HCl
Polyester could be formed from two different monomers:
HOOC-R-COOH + HO-R-OH → HOOC-R-COO-R-OH
Or one monomer:
HOOC-R-OH + HOOC-R-OH → HOOC-R-OOC-R-OH
Use your
knowledge of
reactions!
KOH(aq)
How are you
going to
substitute Br
for OH?
What type of
chemical is
this? What
will it do to
OH?
HOOC(CH2)6COOH
PCl5 or PCl3 or SOCl2
How will you
get from this
to an acyl
chloride?
How are you
going to
substitute Br
with NH2?
NH3(alc)
Look at what
You’re aiming
you have
for an amide
available...
link (COHN)
ClOC(CH2)4COHN(CH2)6NH2
HCl
In
Acid, the
Acids out
only
You worked
Add OH
to the
COOH remains
hydrolyse
the structure
CO group and a
the
polyamides
and NH2 is
of nylon
in and
the
H to
the NH
protonated to
polyesters
previous
Q
group
NH3+
ClOC(CH2)4COHN(CH2)6NH2
ClOC(CH2)4COOH +
+H N(CH ) NH +
H23N(CH22)NH
6
23
Nylon is easily hydrolysed by acid
as it breaks the amide link to form
the 2 monomers.
Teflon is not hydrolysed by acid as
the addition polymer only contains
single C-C bonds that are not easily
broken
-
Draw the 3
monomers next
to each other
first
-
Remove an H from
one side and an
It says ‘repeating’
OH from the
so make the ends
other to form
open ended with a
ester links
bond