Amines Flashcards
(9 cards)
1
Q
Recall how a halogenoalkane can form a quarternary ammonium salt.
Reaction?
Conditions?
A
Nucleophilic substitution:
- Haloalkane to primary amine with excess ammonia
- Primary to secondary amine to tertiary amine
- Tertiary amine to quaternary ammonium salt with excess halogenoalkane
2
Q
Recall the base strength of amines.
A
Aliphatic > ammonia > aromatic
3
Q
Explain why aromatic amines are weaker bases than ammonia. [3]
A
- Electrons on the N delocalise into the ring
- Lone pair less readily avaliable so weaker base
4
Q
Explain why primary amines are stronger bases than ammonia. [3]
A
- Alkyl groups push electrons away
- Greater electron density on N atom (positive inductive effect)
- Lone pair is more readily avaliable so stronger base than ammonia
5
Q
Why is ammonia a base?
A
It can accept a proton to form an ammonium ion.
6
Q
Amines are…
A
weak bases
7
Q
Recall how the nitrocompounds can be reduced, using nitrobenzene as an example. Include reagents and conditions.
A
Reagent: Sn / Conc HCl, aqueous NaOH
Conditions: heat under reflux
8
Q
What are the 3 methods of preparing amines?
A
- Reaction of excess ammonia and halogenoalkanes (nucleophilic sub)
- Reduction of nitriles (using catalytic hydrogenation or LiAlH4)
- Reduction of nitrocompounds to form aromatic amines (using Sn + HCl)
9
Q
Recall how the nitriles can be reduced, usingCH3CN as an example.
A
CH3CN + 4[H] —-> CH3CH2NH2
with LiAlH2 and aqueous ethanol
