Module 6: Chapter 27 - Amines, Amino Acids, and Polymers Flashcards
What are amines?
Amines are organic compounds derived from ammonia, in which one or more of the hydrogen atoms in ammonia have been replaced by a carbon chain or ring
What is an aliphatic amine?
An aliphatic amine is an amine in which the nitrogen atom is attached to at least one straight or branched carbon chain (Alkyl group, R)
What is an aromatic amine?
An aromatic amine is an amine in which the nitrogen atom is attached to an aromatic ring (aryl group)
What is Aniline?
Phenylamine
What are the 3 classifications of amine?
- Primary
- Secondary
- Tertiary
What is a primary amine?
An amine where the nitrogen atom is bonded to 1 carbon atom
What is a secondary amine?
An amine in which the nitrogen atom is bonded to 2 carbon atoms
What is a tertiary amine?
An amine in which the nitrogen atom is bonded to 3 carbon atoms
How do you name amines according to the IUPAC nomenclature rules?
- If it is a simple carbon chain containing an amine group as the highest priority group, simply use the suffix “amine” and name as normal, i.e: butan-2-amine or propan-1-amine
- If the amine group is non-primary (i.e it contains a substituent), name as normal an include “N” rather than a number to identify the location of the substituent, i.e: N-methylbutan-1-amine or N,N-diethylcyclohexanamine
- If there are multiple amine group add “di”, “tri”, “tetra” etc prefix to the amine (and remember to keep full alkane name!), i.e: heptane-1,7-diamine
- If the amine group is not the highest priority group, use the prefix “amino” rather than the suffix, i.e: 4-aminopentan-2-ol or 6-amino-4-oxo-hexanoic acid
What is the distinctive odour of amines?
A foul “fishy” smell
Name this molecule:
butan-2-amine
Name this molecule:
propan-1-amine
Name this molecule:
N-methylbutan-1-amine
Name this molecule:
N,N-diethylcyclohexanamine
Name this molecule:
heptane-1,7-diamine
Name this molecule:
4-aminopentan-2-ol
Name this molecule:
6-amino-4-oxohexanoic acid
What do amines behave as in their chemical reactions?
Bases
Why do amines behave as bases in their chemical reactions?
The lone pair of electrons on the nitrogen atom can accept a proton
What is important to remember when drawing the structure of an amine?
Draw the lone pair on the nitrogen!!!!!
What happens when an amine accepts a proton?
When an amine accepts a proton, a dative covalent bond is formed between the lone pair of electrons on the nitrogen atom and the proton. The amine acts as a base, forming and ammonium ion
What is the reaction between an amine and an acid?
Amine + Acid -> Ammonium Salt
What is the reaction between propan-1-amine and hydrochloric acid?
propan-1-amine + hydrochloric acid -> propylammonium chloride
How do the common names for amines differ from the IUPAC systematic names?
Simple amines are often names as “alkylamines” rather than “alkanamines”
For example:
* IUPAC systematic name = Ethanamine, Common name = Ethylamine
Be aware of this as exam question may use common name!!!
What is the reaction between ethanamine and sulfuric acid?
ethanamine + sulfuric acid -> ethylammonium sulfate
How can you form a primary aliphatic amine?
React ammonia with a haloalkane in ethanolic conditions to produce an ammonium salt. Then add an aqueous alkali (such as NaOH) to generate the amine from the salt
Explain how a primary aliphatic amine can be formed from a haloalkane
- Ammonia has a lone pair of electrons which allows it to act as a nucleophile in a nucleophilic substitution reaction with a haloalkane.
- The product of this substitution is an ammonium salt
- Aqueous alkali (such as NaOH) is then added to generate the amine from the salt
What is the reaction for forming a primary aliphatic amine from a haloalkane?
- Salt formation: Haloalkane + ammonia -> ammonium salt
- Amine formation: Ammonium salt + aqueous alkali -> primary amine + salt + water
Explain the conditions for the formation of a primary aliphatic amine from a haloalkane?
- Ethanol is used as the solvent. This prevents any substitution of the haloalkane by water to produce alcohols
- Excess ammonia is used. This reduces further substituion of the amine group to form secondary and tertiary amines
How can you form secondary and tertiary amines?
React a primary/secondary amine with a haloalkane in ethanolic conditions to produce an ammonium salt. Then add an aqueous alkali (such as NaOH) to generate the amine from the salt
Explain how a secondary/tertiary aliphatic amine can be formed from a haloalkane
- A primary amine has a lone pair of electrons on the nitrogen atom which allows it to act as a nucleophile in a nucleophilic substitution reaction with a haloalkane.
- The product of this substitution is an ammonium salt
- Aqueous alkali (such as NaOH) is then added to generate the amine from the salt
A tertiary amine can also be formed by the further reaction of a secondary amine with a haloalkane
What is the reaction for forming a secondary/tertiary aliphatic amine from a haloalkane?
Salt formation: Haloalkane + primary amine -> ammonium salt
Amine formation: Ammonium salt + aqueous alkali -> secondary amine + salt + water
A tertiary amine can also be formed by the further reaction of a secondary amine with a haloalkane
How can you produce aromatic amines (specifically phenylamine)?
Phenyl amine is produced by the reduction of nitrobenzene. This is done by heating nitrobenzene under reflux with tin and hydrochloric acid to produce the ammonium salt. This is then reacted with excess sodium hydroxide to produce the aromatic amine, phenylamine. The tin and hydrochloric acid act as a reducing agent
What is the reaction for the production of an aromatic amine (specifically phenylamine)?
What are the reagents for the production of an aromatic amine (specifically phenylamine)?
- Nitrobenzene + Hydrochloric acid and tin
- Excess sodium hydroxide
What is the reducing agent in the reduction of nitrobenzene?
Hydrochloric acid and tin
How can you produce an amine from an ammonium salt?
React it with sodium hydroxide
What is the reaction between an ammonium salt and sodium hydroxide?
Ammonium salt + sodium hydroxide -> amine + salt + water
What is an amino acid?
An amino acid is an organic compound containing both amine, NH₂, and carboxylic acid, COOH, functional groups
What is an α-amino acid (alpha amino acid)?
An amino acid in which the amine group is attached to the α-carbon atom - the second carbon atom, next to the carboxyl group
What are the α (alpha), β (beta), and γ (gamma) carbon atoms?
- The α-carbon atom is the second carbon atom. It is the carbon atom that is attached to the carbon atom of the functional group
- The β-carbon atom is the third carbon atom
- The γ-carbon atom is the fourth carbon atom
What is the general formula of an α-amino acid?
RCH(NH₂)COOH
What is significant about the amino acids found in the body?
There are 20 common amino acids in the body that can be built into proteins. They are all α-amino acids
What is a β-amino acid (beta amino acid)?
An amino acid in which the amine group is attached to the β-carbon atom - the third carbon atom
What is a γ-amino acid (gamma amino acid)?
An amino acid in which the amine group is attached to the γ-carbon atom - the fourth carbon atom
What reactions do amino acids have?
Amino acids have the reactions similar to both carboxylic acids and amines as they contain both functional groups
What is the reaction of an amino acid with acids?
The amine group of amino acids is basic and so reacts with acids to form salts:
Amino acid + acid -> ammonium salt
What is the reaction of an amino acid with aqueous alkalis?
The carboxylic acid group is acidic and can react with alkalis to form salts and water:
Amino acid + aqueous alkali -> carboxylate salt + water
What is the reaction of an amino acid with alcohols (in the presence of concentrated sulfuric acid)?
The carboxylic acid group can react with an alcohol in an esterification reaction and the acidic conditions of the reaction protonate the basic amine group:
Amino acid + alcohol + concentrated sulfuric acid -> ester + water
How are amide groups common in nature?
Amide groups are found in nature as the amine and carboxylic acid in amino acids bond together to form proteins
What are optical isomers?
Stereoisomers that are non-superimposable mirror images of each other; they are known as “enantiomers”
What is optical isomerism?
Optical isomerism is a type of stereoisomerism that is found in molecules that contain a chiral centre. The presence of a chiral centre leads to the existence of two non-superimposable mirror image structures. These 2 molecules are known as optical isomers or enantiomers
What are enantiomers?
Optical isomers
How many optical isomers are there for a molecule?
For each chiral centre the molecule contains, there is one pair of optical isomers
What is a chiral centre?
An atom in a molecule that is bonded to four different chemical species, allowing for optical isomerism
What is the chiral centre in organic chemistry?
A carbon atom that is attached to four different atoms or groups of atoms
Where is optical isomerism observed in amino acids?
All α-amino acids (with the exception of glycine) contain a chiral carbon atom and there exhibit optical isomerism. The general structure of an α-amino acid is shown below and the chiral carbon is marked with an asterisk
What is glycine?
It is the simplest α-amino acid and has the structural formula “H₂NCH₂COOH”
Explain why glycine does not have an enantiomer
Glycine has the structural formula “H₂NCH₂COOH”. As it does not contain a chiral centre (the central carbon atom only contains 3 different groups of atoms) it cannot display optical isomerism and therefore does not have an enantiomer
How are pairs of optical isomers drawn?
They are drawn to show the 3D tetrahedral arrangement of the four different groups around the central chiral centre. Once onw has been drawn, the other is drawn as a mirror image, reflecting the first structure
Draw the pair of optical isomers for butan-2-ol:
Identify any chiral carbons in this molecule:
Identify any chiral carbons in this molecule:
Identify any chiral carbons
What is condensation polymerisation?
The joining of monomers, with the loss of a small molecule usually water (the condensation) or hydrogen chloride
Why do enantiomers (optical isomers) have different biological properties?
Different enantiomers fit differently into the various enzymes that drive biochemistry and therefore interact differently with enzymes, proteins, receptors etc of the body
What are 2 examples of condensation polymers?
- Polyesters
- Polyamides
How are polyesters produced?
When making polyesters, monomers are joined together by ester linkages in a long chain to form the polymer. Polyesters can be produced in 2 different ways:
* From one monomer containing both a carboxylic acid group and an alcohol group
* From 2 monomers, one containing 2 carboxylic acid groups and the other conaining 2 alcohol groups
Explain the process of forming polyesters made from one monomer containing 2 different functional groups
For this type of polymerisation, a monomer containing a hydroxyl group, -OH, and a carboxyl group, -COOH, is required. The carboxyl group in one molecule will react with the hydroxyl group in another molecule to form the ester linkage and water.
Draw the repeat unit for the polymer produced in this reaction
Explain the process of forming polyesters made from two different monomers, each containing 2 identical functional groups
For this type of polymerisation, a monomer containing 2 hydroxyl groups, -OH, known as a diol is required and a monomer containing 2 carboxyl groups, -COOH, known as a dicarboxylic acid is required. A carboxyl group in a dicarboxylic acid will react with a hydroxyl group in a diol to form the ester linkage and water.
Draw the repeat unit for the polymer formed in this reaction
What is the general equation for the formation of a polyester formed from 2 different monomers?
n dicarboxylic acid + n diol -> n repeat units + 2n-1 H₂O
How are polyamides produced?
When making polyamides, monomers are joined together by amide linkages in a long chain to form the polymer. Polyamides can be produced in 2 different ways:
* From one monomer containing both a carboxylic acid (or acyl chloride) group and an amine group
* From 2 monomers, one containing 2 carboxylic acid (or acyl chloride) groups and the other conaining 2 amine groups
Explain the process of forming polyamides made from one monomer containing 2 different functional groups
Amino acids contain both an amine group and a carboxylic acid group. Amino acids undergo condensation polymerisation to form polypeptides or proteins (polyamides). The amine group in one molecule will react with the carboxylic acid (or acyl chloride) group in another molecule to form the ester linkage and water (or hydrogen chloride).
What do amino acids react with each other to form?
Polypeptides/proteins (polyamides) in a condensation polymerisation reaction
What are polypeptides/proteins?
They contain many different amino acids all linked together by amide bonds. Therefore they are polyamides
Explain the process of forming polyamides made from two different monomers, each containing 2 identical functional groups
For this type of polymerisation, a monomer containing 2 carboxyl groups (or acyl chloride groups) known as a dicarboxylic acid (or di acyl chloride) is required and a monomer containing 2 amine groups, known as a diamine is required. A carboxyl group in a dicarboxylic acid (or an acyl chloride group) will react with an amine group in a diamine to form the amide bond and water (or hydrogen chloride).
One reaction using a dicarboxylic acid and the other using a diacyl chloride
What is the general equation for the formation of a polyamide formed from 2 different monomers?
- n diamine + n dicarboxylic acid -> n repeat units + 2n-1 H₂O
- n diamine + n diacyl chloride -> n repeat units + 2n-1 HCl
What is hydrolysing condensation polymers?
Polyesters and polyamides can be hydrolysed by using a hot aqueous alkali, such as Sodium Hydroxide, or by using a hot aqueous acid, such as hydrochloric acid.
What are the products of the base hydrolysis of a polyester?
- Dicarboxylate salt
- Diol
What are the products of the acid hydrolysis of a polyester?
- Dicarboxylic acid
- Diol
Draw the products of the base hydrolysis of this molecule:
Dicarboxylate salt + diol
Draw the products of the acid hydrolysis of this molecule:
diol + dicarboxylic acid
What are the products of the base hydrolysis of a polyamide?
- Dicarboxylate salt
- Diamine
What are the products of the acid hydrolysis of of a polyamide?
- Dicarboxylic acid
- Diammonium ion
Draw the products of the base hydrolysis of this molecule:
Dicarboxylate salt + diamine
Draw the products of the acid hydrolysis of this molecule:
diammonium ion + dicarboxylic acid
What is used in base hydrolysis?
hot aqueous alkali - such as sodium hydroxide
What is used in acid hydrolysis?
hot aqueous acid - such as hydrochloric acid
Identify the repeat unit and monomers for this polymer:
Draw the products of acid and alkanline hydrolysis for this molecule:
Draw the products of acid and alkanline hydrolysis for this molecule:
What is the order of the base strength of amines?
- Tertiary amines
- Secondary amines
- Primary amines
- Ammonia
- Aromatic amine
Explain the order of the base strength of amines:
The more alkyl groups that are subsituted onto the N atom in place of H atoms, the more electron density is pushed onto the N atom. This is due to inductive effect of alkyl groups compared to H atoms. Therefore, the more alkyl groups, the higher the electron density of the lone pair on the N, so the stronger the base. However, with aromatic amines, the lone pair on the N atom partially delocalises into the benzene ring, leading to a reduction in the electron density on the N atom - decreasing the base strength
Give both the common name and IUPAC systematic name for this molecule:
Common name: Diethylamine
IUPAC systematic name: N-ethylethanamine
Give both the common name and IUPAC systematic name for this molecule:
Common name: N,N-dimethylpropylamine
IUPAC systematic name: N,N-dimethylpropan-1-amine
What are the properties of optical isomers?
Optical isomers are optically active. This means that they rotate plane polarised light. One enantiomer will rotate the plane polarised light in a clockwise direction and the other rotates it by the same amount but in an anticlockwise direction.
