Chapter 28- Amines Flashcards
What are amines and what are their classes?
Amines are produced when one or more H atoms in ammonia are replaced by an organic group.
They can be primary, secondary or tertiary depending on the number of organic groups.
How are amines produced via nucleophilic substitution?
Haloalkane reacts with two ammonia molecules in nucleophilic substitution to produce a primary amine and ammonium salt.
What happens if there is excess haloalkane during nucleophilic substitution to produce amines?
Amines produced are nucleophiles and can react with haloalkane in nucleophilic substitution so 2°, 3° amines and quaternary ammonium cations can be produced
What is a quaternary ammonium cation?
After all hydrogens of N are replaced, the N can bond with a fourth R group so it has a positive charge and a quaternary ammonium cation is produced
What is the problem with production of amines via nucleophilic substitution and how is it solved?
With excess haloalkane, many possible subs can occur so multiple products are produced. Reaction has low efficiency and reaction conditions have to be changed to cause one sub.
Excess ammonia can be used to produce just 1° amine or mixture can be separated using fractional distillation
How are amines produced via reduction of nitriles?
Nitriles reduced via hydrogenation, requires LiAlH4 in acidic conditions or hydrogen and nickel catalyst (catalytic hydrogenation).
C N triple bond becomes CH2NH2
What is the benefit of producing amines through reduction of nitriles?
Only one possible product meaning reaction has higher efficiency than Nu sub method and no separation of products required
How can amines be produced from nitrobenzenes?
Aromatic amines can be produced from nitrobenzenes through reduction with concentrated HCl and tin catalyst.
-NO2 group becomes -NH2
What are cationic surfactants?
Molecules that are complex with a positive and negative end making the good conditioners as each end is attracted to different substances, preventing static from building up on surfaces. They are useful in industry.
Why do amines have base properties?
Amines are weak bases as the nitrogen atom has a lone pair of electrons available to donate to H+ ions
How does base strength of amines vary?
Base strength depends on how available the lone pair of electrons is to bond with H+ ions, more available stronger the base
How does availability of the lone pair vary with different groups so how do different amine’s base strength compare?
Benzene rings- negative inductive effect, draw electron density away from N making lone pair less available
Alkyl R groups- positive inductive effect, push electron density towards N making lone pair more available
So aromatic amines are weaker bases than aliphatic amines
Why do amines have nucleophilic properties and what reactions can they undergo?
Nitrogen’s lone pair is attracted to partial positive regions.
Nu sub replacing halides in haloalkanes.
Nu add elim with acyl chlorides and acid anhydrides
