Unit 3.4.7 - Amines Flashcards
What are amines?
Where one or more of the hydrogens in ammonia is replaced with a functional group
What is a primary amine?
Where one hydrogen has been replaced in ammonia
What is a secondary amine?
Where two hydrogens have been replaced in ammonia
What is a tertiary amine?
Where three hydrogens have been replaced in ammonia
What is a quaternary ammonium ion?
Where a forth functional group had been added to a tertiary amine
What are quaternary ammonium salts?
Where a positively charged ammonium ion has bonded with a negatively charged ion
What types of amines smell similar to ammonia?
Small amines
What do small amines smell of?
Slightly fishy
What do large amines smell of?
Very fishy
What suffix is used to name amines?
-amine
What suffix is used to name quaternary ammonium ions?
-amine ion
What is the difference between aromatic amines and aliphatic amines?
Aromatic amines contain a benzene ring where as aliphatic ones don’t
What is an aromatic amine?
An amine that contains a benzene ring
What is an aliphatic amine?
An amine that doesn’t contain a benzene ring
Amines can act as bronsted-lowry …. ? And why?
Bronsted-lowry bases as they can accept protons as there is a lone pair of electrons on the nitrogen
The strength of an anime as a base depends on what?
How available the nitrogen’s lone pair of electrons is , the more available the more likely it is to accept a proton and the stronger a base it will be
What is the order of the strength of these bases: ammonia, primary aliphatic amines and aromatic amines, from least to most?
Aromatic amines, ammonia, primary aliphatic amines
Why are aromatic amines the weakest base?
The benzene ring draws electrons towards itself and the nitrogen’s lone pair gets partially delocalised into the ring, so the electron density on the nitrogen decreases and so the pair is much less available to accept a proton making it a weak base
Why is ammonia a stronger base than aromatic bases?
They don’t have any aromatic groups to pull the lone pair of electrons away from the nitrogen
Why are primary aliphatic amines the strongest base?
The alkyl group pushes the electron density onto the nitrogen atom and so its electron density increases and so the lone pair is more available to accept a proton making it a strong base
What three ways can you produce aliphatic amines?
1.) By heating a haloalkane with excess ammonia or amine 2.) Reducing a nitrile 3.) Reflux a nitrile with sodium metal and ethanol
What is produced when you heat haloalkanes with excess ammonia?
A mixture of primary, secondary and tertiary amines and quaternary ammonium salts
How would you separate a mixture of primary, secondary and tertiary amines and quaternary ammonium salts?
By fractional distillation
What is the name for the mechanism between ammonia and haloalkanes?
Nucleophilic substitution
Why do you produce a mixture of primary, secondary and tertiary amines and quaternary ammonium salts when you react ammonia with haloalkanes?
Because further hydrogens are substituted
Give the five steps in the reaction between ammonia and haloalkanes.
1.) The NH₃ is attracted to the slightly positive carbon and it attacks it donating a pair of its electrons forming a blind with the carbon 2.) As carbon can only have four bonds, it cause the C-X bond to break releasing X⁻ and leaving an alkyl ammonium salt 3.) This cause the hydrogen to break of the alkyl ammonium salt and join the ammonia to form NH₄⁺ 5.) This leaves a primary amine, and NH₄X
What is the nucleophile in the reaction between ammonia and haloalkanes? and why?
Ammonia - it has a lone pair of electrons
Why do you get further substitutions after reacting ammonia with a haloalkane?
The primary amine still has a lone pair of electrons
Why does substitution stop at quaternary ammonium salts?
There are no more lone pair of electrons
What are surfactants?
Compounds which are partly soluble and partly insoluble in water
What are surfactants with a positive charge called?
Cationic surfactants
What can be used as cationic surfactants?
Quaternary ammonium salts
Which quaternary ammonium salts are suitable to use as cationic surfactants? And why?
Ones with at least one long hydrocarbon tails the long hydrocarbon chain is insoluble in water and positively charged head is soluble
Name two uses of cationic surfactants?
Fabric conditioner and hair products
Why are cationic surfactants used in fabric conditioner or hair products?
When the hair or fabric gets wet they pick up negative charges on their surface, the positively charged part of the surfactant is attracted to his and forms a coating over the surface, this coating prevents the build up of static electricity to keep fabric smooth or hair flat
How can you produce a primary aliphatic amine by reduction?
Mix a nitrile with a strong reducing agent like LiAlH₄, followed by dilute acid
How can you produce a primary aliphatic amine by reflux?
Reflux a nitrile with sodium metal and ethanol
As both LiAlH₄ and Na is too expensive what method is used in industry to make primary aliphatic amines? And what is required for it?
Catalytic hydrogenation by using a metal catalyst such as platinum or nickel at a high temperature and pressure
How can you produce aromatic amines?
By reducing a nitro compound such as nitrobenzene, by heating it under reflux with tin metal and concentrated HCl
What are the two steps in producing aromatic amines?
1.) Heat the nitro compounds with tin metal and concentrated hydrochloric acid under reflux to make a salt 2.) Add sodium hydroxide to turn the salt not an aromatic amine
Draw the general structure of ammonia, a primary amine, a seconday amine, a tertiary amine and a quaternary ammonium ion
Draw an example of a cationic surfactant.
Draw the equation for reducing ethanenitrile used LiAlH4
Draw the equation of the reduction of a nitrobenzene to a aromtic amine.
