Transcript Level 3: Organics Part I

Level 3:
Organics Part II
Amides
Acid Chlorides
Amino Acids
Polymers
Author: J R Reid
Amides - Introduction
Amides look very much like a cross
between amines and carboxylic
acids
There are two types of amides;
primary and secondary. We will
look at these in more detail on the
next page
All (except methanamide) are solid
at room temperature
They have no smell (unlike amines)
They are weak bases compared to
amines
Amides can be found in nature as
Urea (a component of urine and an
important fertiliser)
H 3C
C
O
NH2
Amides - Continued
There are three types of amines: primary,
secondary and tertiary. Unfortunately we use these
words slightly differently than we do with alcohols:
Identify the trend…
Secondary
Primary
O
H 3C
C
NH2
H3C
NH
CH3
C
O
We only need to name primary amides this year.
The names of amides has the suffix “–amide” e.g.
ethanamide, octanamide…etc
Amides – Reactions
Making amides
Acid chlorides and concentrated ammonia
H3C
C
Cl
+
H3C
NH3
C
NH2
+
HCl
O
O
Esters and concentrated ammonia
H3C
C
O
CH3
+
H3C
NH3
C
+
NH2
H3C
OH
O
O
Hydrolysis
Amides can be hydrolysed (they can break up water) in
acid and alkaline conditions:
H3C
C
NH2
+
+
H3O
H3C
O
H3C
C
O
C
+
OH
+
NH4
O
NH2
+
-
HO
H3C
-
C O
O
+
NH3
Acid Chlorides Introduction
(Acyl Chorides)
As we have seen earlier acid
chlorides can be used to make
amides
They are very similar in
structure to carboxylic acids
except the –OH is replaced by
a –Cl
They are very reactive and
acidic organic compounds
Their names end in the
suffixes –oyl chloride e.g.
propanoyl chloride
H 3C
C
Cl
O
Acid Chloride Introduction II
Acid chlorides are strongly polar. This a low
melting point, but they don’t dissolve in water (see
why on the next page)
They are so reactive that they even react with water
vapour in the air to give a fuming appearance (the
production of HCl gas)
Production – Acid chlorides don’t survive long in
nature, so they have to be made in the lab:
Acid chlorides are made by the nucleophilic substitution
of carboxylic acids with PCl5, SOCl2, and PCl3 e.g.
H3C
C
O
OH
+
PCl 5
H3C
C
O
Cl
+ POCl 3
+
HCl
Acid Chlorides - Reactions
Reactions of acid chlorides:
Hydrolysis – acid chlorides can break
water apart
H3C
C
Cl
+ H 2O
H3 C
C
+
OH
HCl
O
O
Condensation – (esterification)
H3C
C
O
Cl
+
H3C
OH
H3C
C
O
CH3
+
O
Amide production – as we saw earlier
HCl
Amino Acids
Amino acids are the building blocks
of all proteins. There are many
different amino acids but they all
have two things in common:
R
H2 N
Amino – they have an amine group
attached somewhere to their
structure
Acid – they also have a carboxylic
acid group
Amino acids can be linked together
into long chains called
polypeptides (or proteins). The
bonds between two amino acids is
called a peptide bond
A peptide bond is a bond formed
between the carboxylic acid group
and a neighbouring amine group
bond (releasing water as a
byproduct)
C
C
H
O
OH
R
R
H2N
C
C
H
O
OH
H
R
H2N
+ H2N C C OH
O
R
C
C
NH C
C
H
O
H
O
OH
Other Polymers
Polymers are made up of small units (monomers)
that are linked together into long, repeating chains.
We saw on the previous page one example: The
monomer is an amino acid. When linked together it
forms a chain, a polymer called a polypeptide
There are a number of different types of polymers.
Chemists have grouped some together based on
how they are made:
Addition polymers – these link together with no byproducts. This is normally because to the breaking of a
double bond
Condensation polymers – these produce a by-product
(normally water) when the monomers link together
Polymers II
Addition polymers
Examples of addition polymers are: Polythene (many ethenes),
poly vinyl chloride (PVC), polypropylene and polystyrene
Polythene is made by linking together many ethene molecules:
H
H
C
+
C
H
H
H
H
H
H
C
H
+
C
H
C
+
C
H
H
H
H
C
H
H
H
H
H
H
H
H
H
C
C
C
C
C
C
C
C
H
H
H
H
H
H
H
H
H
C
H
H
Condensation polymers
Examples of condensation polymers include: Polyesters,
polypeptides (proteins), polyamides and polysaccharides (many
sugars)
See the next page for examples of these polymers
Polymers - Examples
Polyester
A polyester is created by reacting carboxylic acids and alcohols together.
In order to create long chains of them the chemicals need to be ‘double
ended.’ The two ended alcohol is called a ‘dialcohol’, and the two ended
carboxylic acid is called a ‘dicarboxylic acid’
CH
HO
C
CH
C
O
CH
C
CH
C
OH
+
HO
CH2 CH2 OH
O
C
C
C
O
O
CH
H
CH
CH
C
O
CH2 CH2 O
H
O
CH
Polyamide
A polyamide is a sort of long chain secondary amide. These are created
from double ended amines (diamines) and carboxylic acids (dicarboxylic
acids) reacting
H
N
H
R
N
H
H
+
HO
C
O
R
C
O
OH
H
N
H
R
N
C
H
O
R
C
O
H
Polysaccharides – another
polymer
Sugars such as glucose can be turned into polymers for food
storage. If we link many glucose molecules we create the
chemical we know as starch
Simple sugars (monosaccharides) bonded in pairs are called
disaccharides. An example of this is sucrose (cane sugar)
H
C
C
H
H
OH C
OH
O
H
C
H
C
+
OH
H
C
H
O
C
C
H
H
OH C
OH
OH
H2COH
H
C
H2COH
H2COH
H2COH
O
H
C
H
C
+
OH
H
H
C
H
C
OH
OH
H
C
O
H
C
C
O
H
H
OH C
H
C
OH
OH
H2COH
O
C
H
C
H
C
OH
OH
H2COH
O
H
H
C
H
C
OH
OH
H
C
O
H
C
C
O
H
H
C
H
C
OH
OH
H
C
O
H