Amines
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What are amines derivatives of?
Ammonia
What is the structure of a primary amine?
RNH2
What is the structure of a secondary amine?
R2NH
What is the structure of a tertiary amine?
R3N
What is the reactivity of amines important for?
Useful as intermediates in the synthesis of new molecules.
How do you name amines?
Using the suffix -amine.
Describe the shape of ammonia.
Pyramidal molecule. Bond angles 107 Lone pair on NH3 repels more than the bonding pairs.
Are amines polar?
Yes
How do primary amines form hydrogen bonds?
Using their NH2 group.
Describe the strength of the hydrogen bonds in primary amines?
Weaker than those of alcohols as nitrogen is less electronegative than oxygen. Thus the boiling points of primary amines are less than those of alcohols.
What are short chain primary amines at room temperature?
Gases
What are longer chain primary amines at room temperature?
Volatile liquids
What smell do primary amines have?
Fishy. These smells are produced when proteins decompose.
Describe the solubility of amines.
Primary amines with a chain length of up to 4 carbons are very soluble in water and in alcohols because they form hydrogen bonds with these solvents.
Describe the reactivity of amines.
Amines have a lone pair of electrons. The lone pair can be used to form a bond with a H+ ion when the amine acts as a base or an electron deficient carbon atom when the amine acts as a nucleophile. Also they have a polar N-H bond.
Why is phenylamine not very soluble?
The benzene ring can’t form hydrogen bonds.
Why are amines a Bronsted Lowry Base?
They can accept a proton.
What is formed when an amine reacts with an acid?
Salts which are ionic compounds. These crystallise as the water evaporated.
What does the strength of a base depend on?
How readily it will accept a proton.
Describe the inductive effect of amines.
Alkyl groups release electrons away from the alkyl group and towards the nitrogen atom. This is shown by an arrow. The inductive effect of the alkyl group increases the electron density on the nitrogen atom and thus makes it a better electron pair donor. Thus primary alkylamines are stronger bases than ammonia.
Why are secondary alkylamines stronger bases the primary alkylamines?
They have two inductive effects.
Why are tertiary alkylamines not stronger bases than secondary ones?
Tertiary alkylamines are less soluble in water.
Order ammonia,ethylamine and phenylamine from strongest base to weakest base?
Ethylamine>Ammonia>Phenylamine
What does the lone pair of electrons from an amine do?
Attacks positively charged carbon atoms. Acts as nucleophiles.