Amines Flashcards
(23 cards)
What is the shape of primary amines?
Pyramidal
What is the bond angle of a primary amine?
107 degrees
Why are the H bonds between amines less strong than the H bonds between alcohols?
N is less electronegative than O.
What is the solubility of primary amines?
Up to four, are very soluble in water and alcohols as they form H bonds with them.
What is the reactivity of amines?
They have a lone pair of electrons which can form a bond with,
- H+, when the amine is acting as a base
- electron-deficient C atom, when amine is acting as a nucleophile
What are amines called when they act as a base/ accept a H+ ion?
Bronsted Lowry bases
What forms when an amine reacts with acids?
Salts- which as ionic compounds and will crystallise as the water evaporates.
What happens if a strong base (NaOH) is added to the ionic compound?
Regenerates the insoluble amine.
What does the strength of bases depend on?
How readily it will accept a proton.
What do alkyl groups do in terms of electrons?
Release electrons.
Why are tertiary alkylamines not stronger bases than secondary?
Less soluble in water
What do aryl groups do in terms of electrons?
Withdraw electrons.
Why do aryl groups withdraw electrons?
Because the lone pair of electrons on the N overlaps with the delocalised system on the benzene ring.
What is produced when ammonia reacts with a halogenoalkane?
A mixture of primary, secondary, tertiary and quaternary ammonium salts.
How do you get a better yield of primary amine when reacting ammonia with a halogenoalkane?
Large excess of ammonia
What are the steps for producing amines?
- Halogenoalkanes react with cyanide ion in aq ethanol. Cyanide ion replaces the halide ion by nucleophilic substitution.
- Nitriles then reduces to primary amines with Ni/H2 catalyst. (Only primary amine formed)
What catalyst is used to reduce nitriles to primary amines?
Ni/H2
What are the steps for producing phenylamine?
- Benzene reacted with conc. HNO3 and conc. H2SO4 to produce nitrobenzene.
- Nitrobenzene is reduced to phenylamine using a Sn/HCl catalyst.
- The salt is formed (as HCl us used) and NaOH is added yo liberate the free amine.
What catalyst is used to reduce nitrobenzene to phenylamine?
Sn/HCl
What is formed when an amine reacts with acids chlorides and acid anhydrides?
N substituted amides
What are quaternary ammonium compounds used industrially in the manufacturing of?
Hair and fabric conditioners
How do quaternary ammonium compounds acts as conditioners?
They have a long hydrocarbon chain and a positively charged organic group, so they form cations. Both wet hair and wet fabric pick up negative charges on their surfaces. So the positive charges of the cations attract them to the wet surface and form a coating that prevents the build up of static electricity. This keeps the fabric smooth and prevents fly away hairs.
Why are ammonium compounds called cationic surfactants?
In aq solution the ions cluster with their charged ends in the water and their hydrocarbon tails on the surface.
