Amines Flashcards
What is an amine
Produced when one or more of the hydrogen atoms in ammonia replaced with an alkyl group, primary/secondary/tertiary depending on how many alkyl groups bonded to nitrogen atom
How to name CH3CH2NH3
Ethylamine
How to name benzene ring with amine bonded to it
Phenylamine
Why are tertiary amines insoluble
As cannot form hydrogen bonds as no hydrogen bonded to nitrogen atom
Two factors that affect position of equilibrium of base reacting with water
Tendency of base to attract a proton (availability of electron pair, greater electron density means it is better able to donate lp) and stability of ion formed
How are amines produced
By nucleophilic substitution using ammonia/ reduction of nitriles
How are amines produced from nucleophilic substitution
Reaction between halogenoalkane with ammonia in sealed tube, one mole of halogenoalkane reacts with two moles of ammonia to produce primary amine and ammonium salt (ammonium ion and halide ion), ammonia acts as nucleophile with C delta positive then acts as base to remove H from NH3 to form NH4+ which reacts with halide
How can quaternary amine form
When lone pair on nitrogen atom forms dative covalent bond with R group to form positive ion
How to prevent mixture of products being produced in nucleophilic substitution to produce amines
Use ammonia in excess to form only primary amine so only ammonia acting as nucleophile/ mixture of products can be separated using fractional distillation
How can amines be produced by reduction of nitriles
By hydrogenation requiring reducing agent LiAlH4 in dry ether followed by dilute acid/ or combo of hydrogen gas with nickel catalyst at high temp and pressure
Why are amines weak bases
Because the lp on the nitrogen atom can accept protons
Why is phenylamine the weakest base of amines
As the benzene ring draws electron density away from the nitrogen making the lone pair less available to attract a proton
Why are secondary amines stronger bases than primary
As the extra alkyl group pushes electron density towards the nitrogen atom making the lone pair more available and increases electron density of nitrogen atom
Why do tertiary amines not act as bases
As insoluble as cannot form hydrogen bonds with water
Order of strength as bases for primary/secondary amines/ ammonia and phenylamine
Phenylamine < ammonia < primary amine < secondary amine
How to tell basicity of different amines using pKa values of conjugate acid
The higher the pKa of conjugate acid (weaker acid) the stronger the base eg NH4+ has higher pKa than C6H5NH3+ so NH3 stronger base than C6H5NH2
What is an amide
C=O bonded to NH/NH2
Advantage of reaction from nitrile over halogenoalkane
Produces pure product as no further reactions can occur ( as with lp on nitrogen with delta positive carbon of C-X), do not have to separate products
Equation for hydrogenation of nitrile
CH3CH2CH2CN (butanenitrile) + 2H2 —->CH3CH2CH2CH2NH2 (butylamine)
Equation for reduction of butanenitrile using LiAlH4
CH3CH2CH2CN + 4[H] —->CH3CH2CH2CH2NH2
