Amines Flashcards
What is an amine?
Molecules made from ammonia with 1 or more hydrogen’s replaced by an alkyl chain.
What is the structure for ammonia primary secondary and tertiary amines?
Ammonia:
NH3
Primary amine:
NH2R
Secondary amine:
NHRR’
Tertiary amine:
NRR’R’’
How are primary and secondary amines named?
Via their longest alkyl chain attached and adding the suffix amine is it has priority
Eg 2-ethyl butylamine
Secondary amines names by listing multiple prefixes in alphabetical order and using an indicator N
Eg N-butyl ethylamine
How do amines act as bases?
The lone pair of the nitrogen atom allows amines to accept protons (bronsted lowry bade) or donate a pair of electrons (Lewis base)
Their means amines are weak bases and will form a salt when reacted with a strong acid
What are the two ways in making a primary aliphatic amine?
Mixing with haloalkanes and ammonia
Reducing nitriles with LiAlH4
How are aliphatic primary amines created with haloalkanes and ammonia?
No aromatic ring!
Made by mixing a haloalkane ammonia and ethanol and heating this in a sealed test tube.
It forms a primary amine in two steps of nucleophilic substitution reactions.
Step 1:
Ammonium salt forms
CH3CH2Cl + NH3 ——> CH3CH2NH3Cl
Step 2:
Excess ammonia reactions to form the amine
CH3CH2NH3Cl + NH3 ——> CH3CH2NH2 + NH4Cl
How can primary amines be produced from nitriles?
Reducing nitriles using a reducing agent like LiAlH4 (source of hydride ions) I’m dry ether
RCH2CN + 4[H] ——> RCH2CH2NH2
How can secondary and tertiary aliphatic amines be produced?
By allowing more substitution textiles to take places as the lone pair of the nitrogen atom on the primary amine is able to act as a nucleophile
Use the previous product and another haloalkane
Explain the boiling point trend in amines.
Primary
Secondary
Tertiary
Primary amines can form hydrogen bonds with each other as well as having van der waals forces of attraction between the hydrocarbon chains.
Secondary amines are also able to from hydrogen bonds however having the nitrogen in the middle of the molecule as opposed to the end means that permanent dipole produced is slightly less strong and therefore have lower boiling points.
Tertiary amines have the lowest boiling points as they cannot form hydrogen bonds with themselves ( but can with water) since no hydrogen atoms are attached to the nitrogen.
Explain the solubility of amines in water.
All amines (tertiary included) can form hydrogen bonds with water and therefore are initially soluble. However the larger the hydrocarbon chains attached to the amines, the solubility falls off due to hydrocarbon chains being non polar and therefore not soluble past 6 carbons.
What happens when nitriles undergo hydrolysis? And what do we do to convert this to a carboxylic acid?
Forms an amide which then becomes an ammonium salt (but a slow insignificant reaction)
Use a strong acidic catalyst and heating under reflux to produce a carboxylic acid over an ammonium salt.
What is the inductive effect?
Alkyl groups are able to release electrons towards an adjacent electronegative atom.
Explain the trend in the basic properties of ammonia and primary secondary and tertiary amines and aryl amines.
Ammonia:
Ammonia is able to use its lone pair of electrons to accept hydrogen atoms and act as a base
Primary amines:
In Alkyl amines the alkyl group can release electrons towards the nitrogen atom (inductive effect) allowing the electrons of a primary amine to be donated more easily and hence allowing the primary amine to act as a stronger base than ammonia.
Secondary amines:
Secondary amines have more alkyl groups and therefore a more amplified inductive effect and are hence even stronger bases
Tertiary amines:
Although they have more alkyl groups, they are less soluble in water and therefor are not strong bases
Aryl amines:
Aryl amines are electron withdrawing as the electrons are attracted to the delocalised system of electrons in the benzene ring. Hence being weaker bases.
What happens when we mix amines and acyl chlorides?
Amines act as nucleophiles in addition elimination reactions with acyl chlorides.
They produce N-substituted amides.
How are aromatic amines produced?
Made by reducing nitroarenes
Reduced by refluxing them with a mixture of tin and concentrated HCL @100 degrees. Then adding sodium hydroxide In order to remove the excess acid.
