Post on 15-May-2020
ESTERS ORGANIC AND BIOLOGICAL CHEMISTRY
• Esters are organic compounds which contain the functional
group –COO–
• Properties:
– Volatile – they are liquids that become vapours easily
– Distinctive smells, commonly sweet and ‘fruity’
Ester Functional Group
Preparation of Esters - Esterification
• Esters are derived from a carboxylic acid and an alcohol
CARBOXYLIC ACID ALCOHOL
Preparation of Esters - Esterification
• Esters are derived from a carboxylic acid and an alcohol
• Esters are formed by reacting a carboxylic acid and an
alcohol under reflux conditions in the presence of an acid
catalyst to produce an ester and water.
– Reactions that produce water in this way are called
condensation reactions.
heat
Preparation of Esters - Esterification
• Esters are derived from a carboxylic acid and an alcohol
• Esters are formed by reacting a carboxylic acid and an
alcohol under reflux conditions in the presence of an acid
catalyst to produce an ester and water.
– Reactions that produce water in this way are called
condensation reactions.
heat
FROM THE CARBOXYLIC ACID
FROM THE ALCOHOL
WATER
You need to be able to:
1. Draw the ester that is prepared from a carboxylic acid
and an alcohol
2. Draw the structure of the carboxylic acid and alcohol
which are used to prepare an ester
Drawing Esters
heat
FROM THE CARBOXYLIC ACID FROM THE ALCOHOL
1. Draw the ester that is prepared from a carboxylic acid and an alcohol
Drawing Esters
CARBOXYLIC
ACID ALCOHOL
1. Draw the ester that is prepared from a carboxylic acid and an alcohol
Drawing Esters
CARBOXYLIC
ACID ALCOHOL
WATER
1. Draw the ester that is prepared from a carboxylic acid and an alcohol
Drawing Esters
CARBOXYLIC
ACID ALCOHOL
WATER
ESTER
1. Draw the ester that is prepared from a carboxylic acid and an alcohol
Drawing Esters
CARBOXYLIC
ACID ALCOHOL
WATER
ESTER
FROM THE
CARBOXYLIC
ACID FROM THE
ALCOHOL
1. Draw the ester that is prepared from a carboxylic acid and an alcohol
Drawing Esters
CARBOXYLIC
ACID ALCOHOL
1. Draw the ester that is prepared from a carboxylic acid and an alcohol
Drawing Esters
CARBOXYLIC
ACID ALCOHOL
WATER
1. Draw the ester that is prepared from a carboxylic acid and an alcohol
Drawing Esters
CARBOXYLIC
ACID ALCOHOL
WATER
ESTER
1. Draw the ester that is prepared from a carboxylic acid and an alcohol
Drawing Esters
CARBOXYLIC
ACID ALCOHOL
WATER
ESTER
2. Draw the structure of the carboxylic acid and alcohol which are used to
prepare an ester
Drawing Esters
ESTER
2. Draw the structure of the carboxylic acid and alcohol which are used to
prepare an ester
Drawing Esters
ESTER
2. Draw the structure of the carboxylic acid and alcohol which are used to
prepare an ester
Drawing Esters
ESTER
SPLIT APART Where does the
carbonyl group
come from? The
carboxylic acid or
the alcohol?
REMEMBER:
Water is the
molecule that is
lost.
2. Draw the structure of the carboxylic acid and alcohol which are used to
prepare an ester
Drawing Esters
ESTER
SPLIT APART Where does the
carbonyl group
come from? The
carboxylic acid or
the alcohol?
REMEMBER:
Water is the
molecule that is
lost.
2. Draw the structure of the carboxylic acid and alcohol which are used to
prepare an ester
Drawing Esters
ESTER
SPLIT APART Where does the
carbonyl group
come from? The
carboxylic acid or
the alcohol?
REMEMBER:
Water is the
molecule that is
lost. CARBOXYLIC ACID ALCOHOL
2. Draw the structure of the carboxylic acid and alcohol which are used to
prepare an ester
Drawing Esters
ESTER
SPLIT APART Where does the
carbonyl group
come from? The
carboxylic acid or
the alcohol?
REMEMBER:
Water is the
molecule that is
lost. CARBOXYLIC ACID ALCOHOL
2. Draw the structure of the carboxylic acid and alcohol which are used to
prepare an ester
Drawing Esters
ESTER
2. Draw the structure of the carboxylic acid and alcohol which are used to
prepare an ester
Drawing Esters
ESTER
2. Draw the structure of the carboxylic acid and alcohol which are used to
prepare an ester
Drawing Esters
ESTER
SPLIT APART Where does the
carbonyl group
come from? The
carboxylic acid or
the alcohol?
REMEMBER:
Water is the
molecule that is
lost.
2. Draw the structure of the carboxylic acid and alcohol which are used to
prepare an ester
Drawing Esters
ESTER
SPLIT APART Where does the
carbonyl group
come from? The
carboxylic acid or
the alcohol?
REMEMBER:
Water is the
molecule that is
lost.
2. Draw the structure of the carboxylic acid and alcohol which are used to
prepare an ester
Drawing Esters
ESTER
SPLIT APART Where does the
carbonyl group
come from? The
carboxylic acid or
the alcohol?
REMEMBER:
Water is the
molecule that is
lost.
CARBOXYLIC ACID ALCOHOL
2. Draw the structure of the carboxylic acid and alcohol which are used to
prepare an ester
Drawing Esters
ESTER
SPLIT APART Where does the
carbonyl group
come from? The
carboxylic acid or
the alcohol?
REMEMBER:
Water is the
molecule that is
lost.
CARBOXYLIC ACID ALCOHOL
• Esters are systematically named based upon the
carboxylic acid and alcohol from which they are prepared
Systematic Naming of Esters
CARBOXYLIC ACID ALCOHOL
The R group from the carboxylic acid forms the base
name of the ester.
The –ic ending is changed to –oate. (eg. If the carboxylic acid name is ethanoic acid, the contribution to the
systematic ester name is ethanoate)
The R group from the alcohol is named as an alkyl
group with the ending –yl. (eg. If the alcohol name is methanol, the contribution to the systematic ester
name is methyl)
Systematic Naming of Esters
CARBOXYLIC
ACID ALCOHOL
The systematic name of the ester is written with the
contribution from the alcohol first, followed by the
contribution from the carboxylic acid. (eg. Contribution from the alcohol is methyl and contribution from the
carboxylic acid is ethanoate, so the systematic ester name is
methyl ethanoate)
Systematic Naming of Esters
CARBOXYLIC
ACID ALCOHOL
Systematic Naming of Esters
CARBOXYLIC
ACID ALCOHOL
This ester is prepared from the following carboxylic acid and alcohol:
BUTANOIC ACID METHANOL
Systematic Naming of Esters
CARBOXYLIC
ACID ALCOHOL
This ester is prepared from the following carboxylic acid and alcohol:
BUTANOIC ACID METHANOL
Contribution to ester name: butanoate Contribution to ester name: methyl
Systematic Naming of Esters
CARBOXYLIC
ACID ALCOHOL
This ester is prepared from the following carboxylic acid and alcohol:
BUTANOIC ACID METHANOL
Contribution to ester name: butanoate Contribution to ester name: methyl
The systematic name of the ester is
methyl butanoate
Systematic Naming of Esters
CARBOXYLIC
ACID ALCOHOL
This ester is prepared from the following carboxylic acid and alcohol:
Systematic Naming of Esters
CARBOXYLIC
ACID ALCOHOL
This ester is prepared from the following carboxylic acid and alcohol:
PENTANOIC ACID BUTANOL
Contribution to ester name: pentanoate Contribution to ester name: butyl
The systematic name of the ester is
butyl pentanoate
• After learning how to draw esters from a carboxylic acid
and alcohol, and vice versa, you should be able to
quickly identify which parts of the molecule come from
which reactant.
• Using this knowledge and what you already know about
the IUPAC naming rules, you have the skills to be able to
name an ester without specifically knowing the names of
the carboxylic acid or alcohol.
Systematic Naming of Esters
CARBOXYLIC
ACID ALCOHOL
Systematic Naming of Esters
CARBOXYLIC
ACID ALCOHOL
Determining the systematic name of an ester without knowing the names
of the carboxylic acid or alcohol from which it is derived
Systematic Naming of Esters
CARBOXYLIC
ACID ALCOHOL
Determining the systematic name of an ester without knowing the names
of the carboxylic acid or alcohol from which it is derived
This part of the molecule comes from the carboxylic acid, so it
will contribute __oate to the ester name.
Systematic Naming of Esters
CARBOXYLIC
ACID ALCOHOL
Determining the systematic name of an ester without knowing the names
of the carboxylic acid or alcohol from which it is derived
This part of the molecule comes from the carboxylic acid, so it
will contribute __oate to the ester name.
This section is named
in a similar way to
naming a normal
carboxylic acid. The
longest carbon chain
in this section of the
molecule contains two
carbons with single
bonds only. So
according to IUPAC
rules, the base name
for the carboxylic acid
would be ethane.
Systematic Naming of Esters
CARBOXYLIC
ACID ALCOHOL
Determining the systematic name of an ester without knowing the names
of the carboxylic acid or alcohol from which it is derived
This part of the molecule comes from the carboxylic acid, so it
will contribute __oate to the ester name.
This section is named
in a similar way to
naming a normal
carboxylic acid. The
longest carbon chain
in this section of the
molecule contains two
carbons with single
bonds only. So
according to IUPAC
rules, the base name
for the carboxylic acid
would be ethane.
The carboxylic acid contribution to the
systematic ester name is ethanoate
Systematic Naming of Esters
CARBOXYLIC
ACID ALCOHOL
Determining the systematic name of an ester without knowing the names
of the carboxylic acid or alcohol from which it is derived
ETHANOATE
This part of the molecule comes from the alcohol, so it will
contribute __yl to the ester name.
Systematic Naming of Esters
CARBOXYLIC
ACID ALCOHOL
Determining the systematic name of an ester without knowing the names
of the carboxylic acid or alcohol from which it is derived
ETHANOATE This section is named
in a similar way to
naming a normal
alcohol. The longest
carbon chain in this
section of the
molecule contains two
carbons with single
bonds only. So
according to IUPAC
rules, the base name
for the carboxylic acid
would be ethane.
This part of the molecule comes from the alcohol, so it will
contribute __yl to the ester name.
Systematic Naming of Esters
CARBOXYLIC
ACID ALCOHOL
Determining the systematic name of an ester without knowing the names
of the carboxylic acid or alcohol from which it is derived
ETHANOATE This section is named
in a similar way to
naming a normal
alcohol. The longest
carbon chain in this
section of the
molecule contains two
carbons with single
bonds only. So
according to IUPAC
rules, the base name
for the carboxylic acid
would be ethane.
The alcohol contribution to the
systematic ester name is ethyl
This part of the molecule comes from the alcohol, so it will
contribute __yl to the ester name.
Systematic Naming of Esters
CARBOXYLIC
ACID ALCOHOL
Determining the systematic name of an ester without knowing the names
of the carboxylic acid or alcohol from which it is derived
ETHANOATE ETHYL
The systematic name of the ester is
ethyl ethanoate
Systematic Naming of Esters
CARBOXYLIC
ACID ALCOHOL
Determining the systematic name of an ester without knowing the names
of the carboxylic acid or alcohol from which it is derived
Systematic Naming of Esters
CARBOXYLIC
ACID ALCOHOL
Determining the systematic name of an ester without knowing the names
of the carboxylic acid or alcohol from which it is derived
From the alcohol = _yl
Three carbons in chain with single bonds = propane
Contribution to systematic ester name = propyl
From the carboxylic acid = _oate
One carbon in chain with single bonds = methane
Contribution to systematic ester name = methanoate
The systematic name of the ester is
propyl methanoate
• Polyesters are molecules that are made up of a
chain of repeating monomers that are held
together by ester groups (links).
• Ester links are created through a condensation
reaction between the monomers.
• Polyesters are very strong and have a range of
uses depending on how they are processed.
Polyesters
• Polyesters are prepared through a condensation
reaction between diol and dicarboxylic acid
monomers
Polyesters
DICARBOXYLIC ACID DIOL
Polyesters
DICARBOXYLIC ACID DIOL
Drawing polyesters
Polyesters
DICARBOXYLIC ACID DIOL
Drawing polyesters
Water
Polyesters
DICARBOXYLIC ACID DIOL
Drawing polyesters
Water
Polyesters
DICARBOXYLIC ACID DIOL
Drawing polyesters
Water
ESTER LINK
Polyesters
DICARBOXYLIC ACID
Drawing polyesters
EXISTING POLYMER CHAIN WITH
FREE ALCOHOL GROUP
Polyesters
DICARBOXYLIC ACID
Drawing polyesters
EXISTING POLYMER CHAIN WITH
FREE ALCOHOL GROUP
Water
Polyesters
DICARBOXYLIC ACID
Drawing polyesters
EXISTING POLYMER CHAIN WITH
FREE ALCOHOL GROUP
Water
Polyesters
DICARBOXYLIC ACID
Drawing polyesters
ESTER LINK
EXISTING POLYMER CHAIN WITH
FREE ALCOHOL GROUP
Water
Polyesters
DIOL
Drawing polyesters
EXISTING POLYMER CHAIN WITH
FREE CARBOXYLIC ACID
Polyesters
DIOL
Drawing polyesters
EXISTING POLYMER CHAIN WITH
FREE CARBOXYLIC ACID
Water
Polyesters
DIOL
Drawing polyesters
EXISTING POLYMER CHAIN WITH
FREE CARBOXYLIC ACID
Water
ESTER LINK
… and these condensation reactions continue to form a long polymer chain.
• Drawing the monomer units which make up a
polyester can be done in the same way to that
for single ester compounds
Polyesters
• Drawing the monomer units which make up a
polyester can be done in the same way to that
for single ester compounds
Polyesters
FROM THE
DICARBOXYLIC ACID FROM THE DIOL
• Drawing the monomer units which make up a
polyester can be done in the same way to that
for single ester compounds
Polyesters
FROM THE
DICARBOXYLIC ACID FROM THE DIOL
SPLIT APART
DIOL MONOMER DICARBOXYLIC ACID
MONOMER
• The polyester that has been shown here is
Polyethene terephthalate (PET)
• The repeating unit of the polyester can be
written in square brackets as shown below:
Polyesters
Polyethene terephthalate (PET)
• Polyethene terephthalate (PET) is commonly
used in:
– Fibres for clothing
– Containers for liquids and foods
– Thermoforming in manufacturing (heating a plastic
sheet which is formed into a desired shape using a
mold)
Polyesters
Esterification
• Successful esterification
reactions require
– Reflux conditions
– Presence of an acid
catalyst
Esterification
Reflux Conditions
• Reflux: a process whereby a reaction mixture is heated
for a prescribed period of time. Involves the use of a
heat source and a condenser.
• Esterification reactions are quite slow, so to achieve a
satisfactory yield in a reasonable time, the reaction
requires an extended period of heating
• Heating – increases reaction rate.
• Condenser – prevents the loss of volatile reactant and
product vapours. Upon cooling the vapours condense
and return to the reaction mixture.
Esterification
Presence of an Acid Catalyst
• Concentrated sulfuric acid is most commonly used.
• Role of the catalyst:
– Speeds up the reaction
– Acts as a dehydrating agent, forcing the equilibrium to the
product side which results in a greater yield of the ester
• Only small amounts of acid catalyst are required.
Ester Hydrolysis
• Esters undergo hydrolysis when refluxed with
aqueous acid or base
• Hydrolysis can be considered as the reverse of
esterification – water is consumed as a reactant
in a hydrolysis reaction
Ester Hydrolysis
Acidic Conditions
• Products of acidic hydrolysis are a carboxylic acid and
an alcohol
• Reaction is catalysed by acid
+
H+
reflux
+
CARBOXYLIC ACID ALCOHOL
Ester Hydrolysis
Acidic Conditions
• Products of acidic hydrolysis are a carboxylic acid and
an alcohol
• Reaction is catalysed by acid
+
H+
reflux
+
CARBOXYLIC ACID ALCOHOL
Ester Hydrolysis
Basic Conditions
• Products of basic hydrolysis are a carboxylate salt and
an alcohol
• Basic conditions created by using a sodium hydroxide
solution
+ reflux
+
CARBOXYLATE
SALT
ALCOHOL
Ester Hydrolysis
Basic Conditions
• Products of basic hydrolysis are a carboxylate salt and
an alcohol
• Basic conditions created by using a sodium hydroxide
solution
+ reflux
+
CARBOXYLATE
SALT
ALCOHOL
• We will be completing an esterification practical
in the laboratory.
• We will be preparing a quantity of the ester ethyl
ethanoate. Three processes will be used during
the practical:
– Esterification (preparation of the ester)
– Distillation (purification of the ester)
– Isolation of the ester (separating the ester
from other compounds)
Summative Esterification Practical
• Esterification – Preparation of the ester
– The reaction mixture will be heated under reflux for 10 minutes and then cooled.
• Distillation – The ester is separated from other components in the
reaction mixture due to differences in boiling point. This leads to greater purity in the ester product.
• Separation – During the distillation, some unreacted alcohol will distil
with the ester.
– Using a separating funnel, the ester can be separated from the alcohol using sodium carbonate – ethanol is very soluble in sodium carbonate, whereas ethyl ethanoate is only slightly soluble. This creates two layers in the funnel, and the layer containing the ester can be obtained.
Summative Esterification Practical
• The write-up for the practical will be due one week from the day of completion of the practical.
• The write-up should include:
– An introduction with relevant chemistry concepts explained
– Hypothesis
– Variables
– Materials list
– Procedure
– Any relevant safety considerations
– Results
– A discussion, including analysis of results, evaluation of procedures and indentification of sources of error
– A conclusion with justification
• The report should be a maximum of 1500 words (NOTE: materials list, procedure, safety considerations and results ARE NOT included in the word count)
Summative Esterification Practical
• As per usual, safety glasses, a lab coat and
closed-in shoes are required for the entire
duration of the practical. Long hair must also be
tied back.
• There is some pre-lab work which must be
completed and checked before beginning the
practical. No extra time will be given if this work
has not been completed prior to the lesson.
Summative Esterification Practical
AMIDES ORGANIC AND BIOLOGICAL CHEMISTRY
Amide Functional Group
• Amides are organic compounds with the functional group –CON–
• The most common example of amides is proteins, where the polypeptide chain is joined together with amide linkages.
• The R’ and R” groups could be hydrogen atoms or other carbon-based groups.
Preparation of Amides- Esterification
• Amides are derived from a carboxylic acid and an amine
CARBOXYLIC ACID AMINE
Preparation of Amides- Esterification
• Amides are derived from a carboxylic acid and an amine
• Amides are formed through a condensation reaction, by
reacting a carboxylic acid and amine under reflux conditions
+ reflux
+
Preparation of Amides- Esterification
• Amides are derived from a carboxylic acid and an amine
• Amides are formed through a condensation reaction, by
reacting a carboxylic acid and amine under reflux conditions
+ reflux
+
Water
Preparation of Amides- Esterification
+ reflux
+
Water
+ reflux
+
Water
Preparation of Amides- Esterification
+ reflux
+
Water
+ reflux
+
Water
+ reflux
+
Water
Preparation of Amides- Esterification
+ reflux
+
Water
+ reflux
+
Water
+ reflux
+
Water
Drawing Amides
You need to be able to:
1. Draw the amide that is prepared from a carboxylic acid
and an amine
2. Draw the structure of the carboxylic acid and amine
which are used to prepare an amide
FROM THE CARBOXYLIC ACID FROM THE AMINE
+ reflux
+
1. Draw the amide that is prepared from a carboxylic acid and an amine
Drawing Amides
CARBOXYLIC
ACID AMINE
1. Draw the amide that is prepared from a carboxylic acid and an amine
Drawing Amides
CARBOXYLIC
ACID AMINE
Water
1. Draw the amide that is prepared from a carboxylic acid and an amine
Drawing Amides
CARBOXYLIC
ACID AMINE
Water
AMIDE
1. Draw the amide that is prepared from a carboxylic acid and an amine
Drawing Amides
CARBOXYLIC
ACID AMINE
Water
AMIDE
FROM THE
CARBOXYLIC
ACID
FROM THE
AMINE
1. Draw the amide that is prepared from a carboxylic acid and an amine
Drawing Amides
CARBOXYLIC
ACID AMINE
1. Draw the amide that is prepared from a carboxylic acid and an amine
Drawing Amides
CARBOXYLIC
ACID AMINE
Water
1. Draw the amide that is prepared from a carboxylic acid and an amine
Drawing Amides
CARBOXYLIC
ACID AMINE
Water
AMIDE
1. Draw the amide that is prepared from a carboxylic acid and an amine
Drawing Amides
CARBOXYLIC
ACID AMINE
Water
AMIDE
2. Draw the structure of the carboxylic acid and amine which are used to
prepare an amide
Drawing Amides
AMIDE
2. Draw the structure of the carboxylic acid and amine which are used to
prepare an amide
Drawing Amides
AMIDE
2. Draw the structure of the carboxylic acid and amine which are used to
prepare an amide
Drawing Amides
AMIDE
SPLIT APART
2. Draw the structure of the carboxylic acid and amine which are used to
prepare an amide
Drawing Amides
AMIDE
SPLIT APART
CARBOXYLIC ACID AMINE
2. Draw the structure of the carboxylic acid and amine which are used to
prepare an amide
Drawing Amides
AMIDE
SPLIT APART
CARBOXYLIC ACID AMINE
2. Draw the structure of the carboxylic acid and amine which are used to
prepare an amide
Drawing Amides
AMIDE
2. Draw the structure of the carboxylic acid and amine which are used to
prepare an amide
Drawing Amides
AMIDE
2. Draw the structure of the carboxylic acid and amine which are used to
prepare an amide
Drawing Amides
AMIDE
SPLIT APART
2. Draw the structure of the carboxylic acid and amine which are used to
prepare an amide
Drawing Amides
AMIDE
SPLIT APART
CARBOXYLIC ACID AMINE
2. Draw the structure of the carboxylic acid and amine which are used to
prepare an amide
Drawing Amides
AMIDE
SPLIT APART
CARBOXYLIC ACID AMINE
Polyamides
• Polyamides are molecules that are made up of a
chain of repeating monomers that are held
together by amide groups (links).
• Amide links are created through a condensation
reaction between the monomers.
Polyamides
• Polyamides are prepared through a
condensation reaction between diamine and
dicarboxylic acid monomers
DICARBOXYLIC ACID DIAMINE
Polyamides
Drawing polyamides
DICARBOXYLIC ACID DIAMINE
Polyamides
Drawing polyamides
DICARBOXYLIC ACID DIAMINE
Water
Polyamides
Drawing polyamides
DICARBOXYLIC ACID DIAMINE
Water
Polyamides
Drawing polyamides
DICARBOXYLIC ACID DIAMINE
Water
AMIDE LINK
Polyamides
Drawing polyamides
EXISTING POLYMER CHAIN WITH
FREE AMINE GROUP DICARBOXYLIC ACID
Polyamides
Drawing polyamides
EXISTING POLYMER CHAIN WITH
FREE AMINE GROUP DICARBOXYLIC ACID
Water
Polyamides
Drawing polyamides
EXISTING POLYMER CHAIN WITH
FREE AMINE GROUP DICARBOXYLIC ACID
Water
Polyamides
Drawing polyamides
EXISTING POLYMER CHAIN WITH
FREE AMINE GROUP DICARBOXYLIC ACID
Water
AMIDE LINK
Polyamides
Drawing polyamides
EXISTING POLYMER CHAIN WITH FREE
CARBOXLYIC ACID GROUP DIAMINE
Polyamides
Drawing polyamides
EXISTING POLYMER CHAIN WITH FREE
CARBOXLYIC ACID GROUP DIAMINE
Water
Polyamides
Drawing polyamides
EXISTING POLYMER CHAIN WITH FREE
CARBOXLYIC ACID GROUP DIAMINE
Water
AMIDE LINK
… and these condensation reactions continue to form a long polymer chain.
Polyamides
• Polyamides can also be prepared through a
condensation reaction between
aminocarboxylic acid monomers
AMINOCARBOXYLIC ACID
Polyamides
AMINOCARBOXYLIC ACID AMINOCARBOXYLIC ACID
Polyamides
AMINOCARBOXYLIC ACID AMINOCARBOXYLIC ACID
Water
Polyamides
AMINOCARBOXYLIC ACID AMINOCARBOXYLIC ACID
Water
Polyamides
AMINOCARBOXYLIC ACID AMINOCARBOXYLIC ACID
Water
AMIDE LINK
Polyamides
• Drawing the monomer units which make up a
polyamide can be done in the same way to that
for single amide compounds
Polyamides
• Drawing the monomer units which make up a
polyamide can be done in the same way to that
for single amide compounds
FROM THE
DICARBOXYLIC ACID FROM THE DIAMINE
Polyamides
• Drawing the monomer units which make up a
polyamide can be done in the same way to that
for single amide compounds
FROM THE
DICARBOXYLIC ACID FROM THE DIAMINE SPLIT APART
DIAMINE MONOMER DICARBOXYLIC ACID
MONOMER
Bonding Between Polyamide Chains
• Polyamides such as nylon and kevlar are strong due to
the interactions that are occurring between polymer
chains.
• Hydrogen bonding – the hydrogen atom bonded to the
nitrogen atom forms a hydrogen bond with the carbonyl
group in the amide link on the adjacent chain.
Amide Hydrolysis
• Amides undergo hydrolysis when refluxed for an
extended period of time under strongly acidic
or basic conditions
• Hydrolysis of amide linkages in proteins occurs
more readily when catalysed by enzymes
Amide Hydrolysis
Acidic Conditions
• Products of acidic hydrolysis are a ammonium or
substituted ammonium salt and a carboxylic acid.
• The reaction uses concentrated hydrochloric acid.
+ reflux
+
+ reflux
+
AMMONIUM SALT CARBOYXLYIC ACID
AMMONIUM CARBOYXLYIC ACID
Amide Hydrolysis
Acidic Conditions
• Products of acidic hydrolysis are a ammonium or
substituted ammonium salt and a carboxylic acid.
• The reaction uses concentrated hydrochloric acid.
+ reflux
+
+ reflux
+
AMMONIUM SALT CARBOYXLYIC ACID
AMMONIUM CARBOYXLYIC ACID
Amide Hydrolysis
Basic Conditions
• Products of acidic hydrolysis are a ammonia or an amine
and a carboxylate salt.
• The reaction uses concentrated sodium hydroxide
solution.
+ reflux
+
+ reflux
+
AMINE CARBOXYLATE SALT
AMMONIA CARBOXYLATE SALT
Amide Hydrolysis
Basic Conditions
• Products of acidic hydrolysis are a ammonia or an amine
and a carboxylate salt.
• The reaction uses concentrated sodium hydroxide
solution.
+ reflux
+
+ reflux
+
AMINE CARBOXYLATE SALT
AMMONIA CARBOXYLATE SALT
TRIGLYCERIDES ORGANIC AND BIOLOGICAL CHEMISTRY
Triglycerides
• Triglycerides are edible fats and oils derived from
plants and animals.
• Triglycerides are triesters – they are made up of a
propane-1,2,3-triol backbone (common name
glycerol) and three long, straight chain carboxylic
acids which are attached to the glycerol backbone with
ester linkages.
– The straight chain carboxylic acids are commonly referred to as
“fatty acids”
Triglycerides
+
• The ester linkages between the fatty acid chains
and glycerol are prepared through a
condensation reaction
ALCOHOL
(GLYCEROL)
CARBOXYLIC ACID
(FATTY ACIDS) TRIGLYCERIDE
Triglycerides
+
• The ester linkages between the fatty acid chains
and glycerol are prepared through a
condensation reaction
ALCOHOL
(GLYCEROL)
CARBOXYLIC ACID
(FATTY ACIDS)
H2O
H2O
H2O
TRIGLYCERIDE
Triglycerides
+
• The ester linkages between the fatty acid chains
and glycerol are prepared through a
condensation reaction
ALCOHOL
(GLYCEROL)
CARBOXYLIC ACID
(FATTY ACIDS)
H2O
H2O
H2O
Glycerol backbone
TRIGLYCERIDE
Ester links
Triglycerides
• The carboxylic acid chains almost always
contain an even number of carbon atoms,
including the carbon atom in the carbonyl group.
• These chains can be saturated (single bonds
only) or unsaturated (contains at least one
double bond)
– If more than one double bond is present in the carbon
chain, it is described as polyunsaturated
Drawing Triglycerides
Drawing triglycerides given the structural formula of the carboxylic
acid(s) from which it is derived
Drawing Triglycerides
Drawing triglycerides given the structural formula of the carboxylic
acid(s) from which it is derived
H2O
H2O
H2O
Drawing Triglycerides
Drawing triglycerides given the structural formula of the carboxylic
acid(s) from which it is derived
H2O
H2O
H2O
Triglycerides Hydrolysis
• Fats and oils are highly concentrated stores of energy.
Triglyceride hydrolysis is required to release this energy
for use in the body.
• Triglyceride hydrolysis is catalysed by enzymes called
lipases. Without these enzymes, hydrolysis would only
be able to occur under severe conditions.
• Water is also required for triglyceride hydrolysis.
• The products of triglyceride hydrolysis is glycerol and
three fatty acid molecules.
Triglycerides Hydrolysis
General equation for hydrolysis
+ +
GLYCEROL 3 FATTY ACID MOLECULES TRIGLYCERIDE
Triglycerides Hydrolysis
General equation for hydrolysis
+ +
GLYCEROL 3 FATTY ACID MOLECULES TRIGLYCERIDE
NOTICE: 3 molecules of water are required
Triglycerides Hydrolysis
Drawing hydrolysis products
Triglycerides Hydrolysis
Drawing hydrolysis products
FROM
GLYCEROL
FROM THE FATTY ACID MOLECULES
Triglycerides Hydrolysis
Drawing hydrolysis products
FROM
GLYCEROL
FROM THE FATTY ACID MOLECULES
SPLIT APART
Triglycerides Hydrolysis
Drawing hydrolysis products
GLYCEROL THREE FATTY ACID MOLECULES
Saturated and Unsaturated Triglycerides
• Triglycerides can be classified as saturated or
unsaturated depending on the fatty acid chains
that they are made of.
SATURATED UNSATURATED
Saturated and Unsaturated Triglycerides
SATURATED TRIGLYCERIDE
(SINGLE BONDS ONLY)
UNSATURATED TRIGLYCERIDE
(DOUBLE BONDS)
Saturated and Unsaturated Triglycerides
• The physical state of a fat or oil is determined by the degree
of unsaturation of the triglyceride.
• Saturated triglycerides
‒ Have an ordered and compact structure, allowing the molecules
to pack very closely together. Fats/oils with a high percentage of
saturated triglycerides are generally solid at room temperature.
• Unsaturated triglycerides
‒ Have a disordered and loose structure, causing the molecules to
not be able to pack closely together. Fats/oils with a high
percentage of unsaturated triglycerides are generally liquid at
room temperature.
Saturated and Unsaturated Triglycerides
• Edible fats are solids at room temperature and are
generally derived from animals.
• Edible oils are liquids at room temperature and are
generally derived from plants or fish.
• Animal fats contain a greater percentage of saturated
triglycerides than vegetable oils.
Melting Point of Fats/Oils
• Melting point increases as the length of the fatty acid
chains in the triglyceride increase. This is caused by
an increase in dispersion forces between triglyceride
molecules.
• Melting points decrease as the degree of
unsaturation (number of double bonds) in the fatty
acid chains increases. This is caused by disordered
and loose packing between molecules. Dispersion forces
are weaker as chains are further apart.
Addition Reactions Across C=C Groups
• Unsaturated molecules – contain C=C double bonds.
• C=C groups can undergo addition reactions with
diatomic molecules such as bromine (Br2)/iodine (I2) and
hydrogen (H2).
Addition Reactions Across C=C Groups
Addition Reactions Across C=C Groups with Bromine (Br2) and Iodine
(I2) = Determining The Degree Of Unsaturation
• The degree of unsaturation of a triglyceride (how many double
bonds in the molecule) can be determined by reacting a
triglyceride solution with bromine (Br2) or iodine (I2).
• After adding Br2 solution, the orange bromine colour
disappears, as the products of the addition reaction are
colourless.
• The degree of unsaturation is determined from the end point
(the point at which no more Br2 reacts with the triyglyceride)
• Addition of I2 across C=C double bonds does not occur as
readily as that for Br2. However, the degree of unsaturation is
usually quoted as an iodine number.
Addition Reactions Across C=C Groups
Addition Reactions Across C=C Groups with Bromine (Br2) and
Iodine (I2) = Determining The Degree Of Unsaturation
Conical flask
containing fat/oil
in cyclohexane
Burette containing
bromine in
cyclohexane
• Add solution of Br2 to known
volume of fat/oil in
cyclohexane
• End point = first sign of
permanent orange colour in
the flask
• The greater the amount of
bromine that reacts, the
greater the degree of
unsaturation
Addition Reactions Across C=C Groups
Addition Reactions Across C=C Groups with Bromine (Br2) and
Iodine (I2) = Determining The Degree Of Unsaturation
+
Addition Reactions Across C=C Groups
Addition Reactions Across C=C Groups with Bromine (Br2) and
Iodine (I2) = Determining The Degree Of Unsaturation
+
Addition Reactions Across C=C Groups
Addition Reactions Across C=C Groups with Bromine (Br2) and
Iodine (I2) = Determining The Degree Of Unsaturation
The iodine/bromine number of a fat or oil is the mass of iodine/bromine as I2 / Br2 that reacts with exactly with
100 grams of the fat or oil. The greater the value of the iodine/bromine number, the greater the
degree of unsaturation.
Addition Reactions Across C=C Groups
Addition Reactions Across C=C Groups with Hydrogen (H2)
= Hydrogenation
• Hydrogenation involves adding across H2 C=C double
bond
• The reaction involves heating a liquid oil with hydrogen
gas under pressure in the presence of a nickel catalyst.
• Using this process on unsaturated fats and oils to be
converted from liquids forms to solid forms.
– Adding H2 decreases the degree of unsaturation (less double
bonds), triglyceride molecules become more ordered and
become able to pack together very closely, hence becoming
solid.
Addition Reactions Across C=C Groups
Addition Reactions Across C=C Groups with Hydrogen (H2)
= Hydrogenation
• Elevated temperature, high pressure and a nickel
catalyst are all used to increase the rate of addition
reaction between the unsaturated molecules and
hydrogen.
– Elevated temperature: increases the energy of colliding
reactant molecules, causing more collisions which lead to the
formation of products.
– High pressure: increases the concentration of the hydrogen
gas, leading to more productive collisions between reactants.
– Nickel catalyst: provides an alternative reaction pathway with a
lower activation energy.
Addition Reactions Across C=C Groups
Addition Reactions Across C=C Groups with Hydrogen (H2)
= Hydrogenation
+
Addition Reactions Across C=C Groups
Addition Reactions Across C=C Groups with Hydrogen (H2)
= Hydrogenation
+
Triglyceride Hydrolysis
• Soap and detergents are able to be produced
when triglycerides are hydrolysed under
alkaline conditions.
• This process is referred to as saponification. – Animal fats or vegetable oils are boiled with concentrated
sodium hydroxide solution
– The products of alkaline conditions are glycerol and three long
chain carboxylate ions
Alkaline Hydrolysis of Triglycerides
+
GLYCEROL 3 CARBOXYLATE IONS
heat
Alkaline Hydrolysis of Triglycerides
CARBOXYLATE ION
• Carboxylate ions have hydrophilic (water loving)
and hydrophobic (water fearing) regions.
• Carboxylate ions in soap are able to move non-
polar substances through aqueous solutions
through micelle formation
Micelles
CARBOXYLATE ION
Polar head group,
hydrophilic
Non-polar hydrocarbon
chain, hydrophobic
• The hydrophobic, non-polar hydrocarbon chain attaches
to the non-polar dirt or grease.
• The hydrophilic, polar head interacts with the polar
water molecules.
• These interactions together create a globule of
dirt/grease.
Micelles
• With some agitation to the system, the globule dislodges
from the surface it is attached to and the carboxylate ions
come together to form spheres called micelles.
Micelles
• The centre of the micelle is hydrophobic and contains
the globules of dirt/grease.
• The ionic heads interact with the polar water because it
is hydrophilic. Since the ionic heads are negatively
charged, micelles repel each other, preventing the
dirt/grease globules from joining back together.
• The interactions between the ionic head and the water
allows the micelle to be soluble in water. As a result,
when the water is washed away, the micelle
(containing the dirt/grease) is also washed away,
leaving a clean surface behind.
PROTEINS ORGANIC AND BIOLOGICAL CHEMISTRY
Amino Acids
General structure of amino acids
AMINE GROUP
CENTRAL CARBON ATOM
ONE OTHER ATOMS OR
GROUP OF ATOMS
(REPRESENTED AS “R”)
CARBOXYL
GROUP
HYDROGEN ATOM
Amino Acids
• Amino acids are the building blocks of proteins. – Proteins are made up of one or more polypeptide chains.
These chains are made up of amino acids that are held together with peptide bonds.
– There are 500 different amino acids, however the human genetic code only directly encodes 20.
Amino Acids
ESSENTIAL amino acids:
must be obtained from the diet.
NON- ESSENTIAL amino acids:
can be synthesised in the body.
Amino Acids
• Amino acids can undergo self-ionisation in a
neutral environment (pH=7.0).
• The product of self-ionisation is a dipolar ion called
a zwitterion.
The amine group has a
pair of non-bonding
electrons, making it a
base capable of
accepting a proton
The carboxyl group
can lose a proton due
to the polarity of the
group
Amino Acids
• Amino acids can undergo self-ionisation in a
neutral environment (pH=7.0).
• The product of self-ionisation is a dipolar ion called
a zwitterion.
ZWITTERION
Amino Acids
Drawing products of self-ionisation (zwitterions)
Amino Acids
Drawing products of self-ionisation (zwitterions)
Amino Acids
pH < 7 (acidic)
pH > 7 (basic)
pH = 7 ZWITTERION
Proteins
• Amino acids can undergo a condensation
reaction to form a polypeptide chain.
• The condensation reaction occurs between the
carboxyl group of one amino acid and the amine
group of another amino acid.
+
AMINO ACID 1 AMINO ACID 2
Proteins
• Amino acids can undergo a condensation
reaction to form a polypeptide chain.
• The condensation reaction occurs between the
carboxyl group of one amino acid and the amine
group of another amino acid.
+
AMINO ACID 1 AMINO ACID 2
H2O
Proteins
• Amino acids can undergo a condensation
reaction to form a polypeptide chain.
• The condensation reaction occurs between the
carboxyl group of one amino acid and the amine
group of another amino acid.
+
AMINO ACID 1 AMINO ACID 2 DIPEPTIDE
H2O
Proteins
• Amino acids can undergo a condensation
reaction to form a polypeptide chain.
• The condensation reaction occurs between the
carboxyl group of one amino acid and the amine
group of another amino acid.
+
AMINO ACID 1 AMINO ACID 2 DIPEPTIDE
H2O
Peptide link
or bond
Remember: proteins are the most common
example of an amide. You may notice that the
peptide bond is the same as an amide bond.
The condensation reaction between a carboxylic
acid and amine is very difficult to achieve in the
laboratory. However in nature this occurs very
readily.
• The continuation of condensation reactions involving many
amino acids forms a long molecule called a polypeptide,
which contains many peptide bonds.
Proteins
Drawing polypeptide chains
+
• The continuation of condensation reactions involving many
amino acids forms a long molecule called a polypeptide,
which contains many peptide bonds.
Proteins
H2O
Drawing polypeptide chains
+
• The continuation of condensation reactions involving many
amino acids forms a long molecule called a polypeptide,
which contains many peptide bonds.
Proteins
H2O
Drawing polypeptide chains
+
• The continuation of condensation reactions involving many
amino acids forms a long molecule called a polypeptide,
which contains many peptide bonds.
Proteins
H2O
Drawing polypeptide chains
+
• The continuation of condensation reactions involving many
amino acids forms a long molecule called a polypeptide,
which contains many peptide bonds.
Proteins
Drawing polypeptide chains
+
EXISTING DIPEPTIDE
• The continuation of condensation reactions involving many
amino acids forms a long molecule called a polypeptide,
which contains many peptide bonds.
Proteins
H2O
Drawing polypeptide chains
+
EXISTING DIPEPTIDE
• The continuation of condensation reactions involving many
amino acids forms a long molecule called a polypeptide,
which contains many peptide bonds.
Proteins
H2O
Drawing polypeptide chains
+
EXISTING DIPEPTIDE
• The continuation of condensation reactions involving many
amino acids forms a long molecule called a polypeptide,
which contains many peptide bonds.
Proteins
H2O
Drawing polypeptide chains
+
EXISTING DIPEPTIDE
• The continuation of condensation reactions involving many
amino acids forms a long molecule called a polypeptide,
which contains many peptide bonds.
Proteins
Drawing polypeptide chains
+
EXISTING POLYPEPTIDE
• The continuation of condensation reactions involving many
amino acids forms a long molecule called a polypeptide,
which contains many peptide bonds.
Proteins
H2O
Drawing polypeptide chains
+
EXISTING POLYPEPTIDE
• The continuation of condensation reactions involving many
amino acids forms a long molecule called a polypeptide,
which contains many peptide bonds.
Proteins
H2O
Drawing polypeptide chains
+
… and these condensation reactions continue to form a long polypeptide chain.
EXISTING POLYPEPTIDE
Protein Structure
• The structure of proteins is described at four levels: primary,
secondary, tertiary and quaternary.
SECONDARY
TERTIARY QUATERNARY
PRIMARY
Protein Structure
Interactions in polypeptide chains
• Peptide bonds are polar. This allows interactions to occur both
within a polypeptide chain and between polypeptide chains or
molecules.
– The secondary structure of a protein refers to the shape the
polypeptide folds or twists into.
– Two main folding patterns: α-helix and β-pleated sheet
– Polypeptide chains are held in these configurations by hydrogen
bonding.
Protein Structure
α-helix β
Protein Structure
Interactions in polypeptide chains
• Peptide bonds are polar. This allows interactions to occur both
within a polypeptide chain and between polypeptide chains or
molecules.
– The tertiary structure of a protein refers to the folding that the
α-helix and β-pleated sheet exhibit.
– The tertiary structure is stabilised by a number of interactions:
• Ionic bonding
• Hydrogen bonding
• Dispersion forces
• Covalent bonding
Protein Structure
Interactions in polypeptide chains
• Peptide bonds are polar. This allows interactions to occur both
within a polypeptide chain and between polypeptide chains or
molecules.
– The quaternary structure of a protein refers to the 3-
dimensional arrangement of more than one polypeptide chain.
– Dispersion forces between non-polar R groups stabilize the
quaternary structure.
Protein Structure
Hydrogen bonding in polypeptide chains
• Hydrogen bonding can also occur between polypeptide chains or
molecules.
Hydrogen
bonding
between chains
Protein Structure
Hydrogen bonding in polypeptide chains
• Hydrogen bonding can also occur between polypeptide chains or
molecules.
Hydrogen
bonding
between protein
chains and water molecules
Protein Denaturation
• The structure of a protein and its biological functions are closely
linked. If the secondary, tertiary or quaternary structure of a
protein is altered, the protein loses it capacity to perform
biological functions.
• Altered structure and hence loss of function is referred to as
denaturation.
• Two factors commonly cause denaturation: pH and temperature
Protein Denaturation
Unravelling of a protein
to the primary structure
(simple polypeptide chain). Function is lost.
Protein Denaturation
All enzymes function at optimum temperature and pH conditions.
Effect of pH
• Increase or decrease in pH effects ionic bonding interactions,
causing structure destabilisation.
Effect of temperature
• Increasing the temperature causes secondary interactions
(dispersion forces, dipole-dipole interactions and hydrogen bonds)
to break, causing the entire protein to unravel to the primary
structure. – Decreasing temperature also impacts on the rate of enzyme activity.
Protein Denaturation
Unravelling of the protein structure results in its active site being no
longer available to catalyse reactions.
pH or temperature
Rate of enzyme
activity
Maximum rate of activity
occurs when the
optimum conditions are
met. The optimum
conditions are unique for each enzyme.