Chapter 27- Amines, Amino Acids and Polymers Flashcards
What is the difference between an aliphatic amine and an aromatic amine ?
- Aliphatic - Nitrogen is attached to at least one straight or branched carbon chain
- Aromatic - Nitrogen is attached to an aromatic ring
What do amines often behave as?
Bases
How do amines behave as bases?
Nitrogen donates electron pair to H+
For the formation of primary amines, what is reacted together in the two steps?
- Haloalkane and salt
- Salt and sodium hydroxide
In primary amine formation, what is in excess and why?
- Ammonia is in excess
- Prevents product from reacting with more of the haloalkane
In primary amine formation, what is the purpose of ethanol?
It prevents substitution of haloalkane by water to produce alcohols
What are the two steps of forming a secondary amine from a primary amine?
- Primary amine + CH3Br and ethanol as solvent
- Salt product + NaOH forms secondary amine
How is phenylamine made from nitrobenzene?
- Nitrobenzene is heated under reflux with tin and HCl to form ammonium salt
- Ammonium salt is reacted with NaOH to produce phenylamine
What do tin and HCl act as in formation of phenylamine from nitrobenzene?
Reducing agents
What is an amino acid ?
An organic compound that contains both an amine and a carboxylic acid group
What do amino acids react similarly to ?
Amines and carboxylic acids
What properties does the amine group have ?
It is basic
What does the amine group react with ?
It reacts with an acid to make a salt
What does the carboxylic acid group react with ?
- Reacts with an alkali to form a salt
- Reacts with an alcohol to form an ester
Amino acid + aqueous alkali reaction
Forms a salt and water
Can amino acids undergo esterification ?
Yes
How do amino acids undergo esterification ?
- Heating with an alcohol
- In the presence of concentrated sulfuric acid
What do the acidic conditions in esterification lead to for an amino acid ?
The acidic conditions protonate the basic amine group of the ester
What is a zwitterion ?
It is when there is both a positive and negative charge present in the structure
Why does a zwitterion arise in an amino acid ?
The basic amine group can accept a proton from the carboxylic acid group
What is the charge of zwitterions ?
It is neutral
What is the isoelectric point of a zwitterion ?
- The pH at which the zwitterion is formed
- Each amino acid has its own unique isoelectric point
What happens when the amino acid is added to a solution with a pH greater than its isoelectric point ?
The amino acid behaves as an acid and loses a proton
What happens when the amino acid is added to a solution with a pH less than its isoelectric point ?
The amino acid behaves as a base and gains a proton
How are amides formed ?
Amides are the products of reactions of acyl chlorides with ammonia and amines
What is optical isomerism ?
It is a type of stereoisomerism
Where is optical isomerism found ?
In molecules that have a chiral centre
What is a chiral centre ?
It is a carbon that is attached to four different atoms or group of atoms
What does the presence of a chiral carbon atom lead to ?
- It leads to the existence of two non-superimposable mirror image structures
- These are known as enantiomers (optical isomers)
What do optical isomers have in common ?
Same physical properties
What are the two monomer types that form polyesters?
- Diols
- Dicarboxylic acids
How can polyesters be formed from one monomer?
- One end has an alcohol group
- One end has a carboxyl group
What is condensation polymerisation?
- Joining of monomers with loss of a small molecule, usually water or HCl
- Two different functional groups are needed
How can polyamides be formed from just one monomer?
Amino acids contain a carboxylic acid and an amine group
How can polyamides be formed from two monomers?
- Diamine
- Dicarboxylic acid
What is the common name for polyamides made from two monomers?
Nylon
What is required to undergo acid hydrolysis?
- Excess HCl
- Water
What is formed from polyester undergoing acid hydrolysis?
- Diol
- Dicarboxylic acid
What is formed from acid hydrolysis of polyamide?
- Diammonium salt
- Dicarboxylic acid
What is required to undergo base hydrolysis?
Excess NaOH
What is formed from polyester undergoing base hydrolysis?
- Diol
- Salt of dicarboxylic acid
What is formed from base hydrolysis of polyamide?
- Diamine
- Salt of dicarboxylic acid
How does addition polymerisation differ from condensation polymerisation with monomers?
- Addition - Monomer contains C=C bond
- Condensation - Two monomers with two functional groups or one monomer with two different functional groups
How does addition polymerisation differ from condensation polymerisation with backbone?
- Addition - Backbone of polymer is -C-C- bond
- Condensation - Polymer back bone contains ester or amide group
