Module 6.2 - Nitrogen compounds, polymers and synthesis Flashcards
How do you get an amine?
If one or more of the hydrogens in ammonia is replaced with an organic group.
If a nitrogen atom is bonded to two alkyl groups and 1 hydrogen atom, what type of amine is it?
Secondary amine.
What makes amines bases?
There’s a lone pair of electrons on the nitrogen atom of an amine that’s able to accept protons (H+ ions).
What is produced when amines are neutralised by acids?
Ammonium salts.
How can aliphatic amines be made from haloalkanes?
Amines can be made by heating a haloalkane with an excess of ethanolic ammonia (ammonia dissolved in ethanol).
Why would you need to separate the products of aliphatic amines using fractional distillation?
In the experiment, you will get a mixture of primary, secondary and tertiary amines and quaternary ammonium salts, as more than one hydrogen is likely to be substituted.
What kind of reaction is the reaction using haloalkanes to form amines?
A nucleophilic substitution reaction.
Describe the 2 steps of how aromatic amines are made by reducing a nitrocompounds such as benzene?
1) Heat a mixture of a nitro compound, tin metal and concentrated hydrochloric acid under reflux - this makes a salt.
2) To get the aromatic amine, you have to add sodium hydroxide.
Why do amides behave differently to amines?
The carbonyl group pulls electrons away from the rest of the -CONH2 group.
What is the functional groups of amides?
-CONH2
What is the general formula of an amino acid?
RCH(NH2)COOH
How can amino acids react with acids and alkalis?
The carboxylic acid in an amino acid can react with an alkali to form a conjugate base which can combine with a positive ion to form a salt. The amine group can also react with an acid to form a salt of the conjugate acid.
How can amino acids form esters?
The carboxylic acid group in an amino acid can react with an alcohol in the presence of a strong acid catalyst (normally sulfuric acid) to form an ester.
What does amino acids being amphoteric mean?
They can act as both acids and bases.
How is a zwitterion formed?
The acidic carboxyl group and the basic amine interact with each other to form a salt called a zwitterion, at a specific pH called the isoelectric point.
What happens to an amine if the pH is increased, more alkaline?
The molecule will have a negative charge, the amine group will lose a hydrogen and equilibrium is driven to the right.
What happens to an amine if the pH is decreased, more acidic?
The molecule will have a positive charge and the O will bond to a hydrogen atom, the equilibrium is driven to the left.
What conditions do you need when preparing an aromatic amine?
> Reducing agent of a mix of HCI and tin.
>100 degrees under reflux.
Why are aliphatic amines stronger bases than aromatic amines?
Aromatic amines donate their lone pairs into the benzene ring making them less potent and therefore, less likely to attract a H+ ion.
What is a chiral (asymmetric) carbon?
One which has 4 different groups attached to it.
What are molecules called that can arrange the groups around the chiral carbon in two different ways?
Enantiomers or optical isomers.
What is an enantiomer?
Mirror images of each other and no matter which may you turn/rotate them, they can’t be superimposed.
What does it mean when optical isomers are optically active?
They rotate plane-polarised light. One enantiomer rotates it in a clockwise direction, the other rotates it the same amount but in an anticlockwise direction.
What are the two types of polymerisation?
Addition and condensation polymerisation.
Describe addition polymerisation?
Where the double bonds open up, and molecules join together to make long chains.
Give 2 examples of condensation polymers?
Polyesters and polyamides.
How can condensation polymerisation be reversed?
Hydrolysis - water molecules are added back in and the links are broken.
In practice is water used to hydrolyse polymers and why is this?
Water isn’t used because hydrolysis with just water is far too slow, so the reaction is done with an acid or base.
Do polyamides hydrolyse faster with acids or bases?
Acids.
What is formed when a polyamide is hydrolysed with an acid?
Dicarboxylic acid and diamine.
Polyesters hydrolyse more easily with a base. What is formed?
Dicarboxylic acid salt and a diol.
