6.2.1 Amines: Module 6: Organic Chemistry & Analysis Chemistry OCR A A Level

How do you name amines?

-amine or amino-

Why are amines so reactive?

The lone pair of electrons on the Nitrogen - due to polar N-H bond.

What shape are amines around the N? Bond angle?

What shape are amines around the N? Bond angle? Trigonal pyramidal, 107° due to lone pair on N.

What kind of intermolecular forces do they have? Why?

Hydrogen bonding due to polar N-H bond and lone pair of electrons on N atom.

Do amines have intermolecular forces which are stronger than or weaker than alcohols? Why?

Weaker, as N has a lower electronegativity than O → Weaker hydrogen bonding

How can/when do amines act as bases?

The lone pair on the nitrogen atom accepts a proton.

How can/when do amines act as nucleophiles?

When they bond with an electron-deficient C atom (donate lone pair from N).

In order to be the strongest base, what must a particular amine have (out of a set of amines)?

Greatest electron density around the N atom, making it a better electron pair donor (attracts protons more).

What effect do alkyl groups have (on electron density and base strength)?

Positive inductive effect - increase electron density around N → stronger base

How can primary amines then form 2°, 3° amines and 4° ammonium ions?

Multiple substitutions; primary amine is a nucleophile that attacks the original haloalkane etc.

What are the problems with this method?

Not efficient as low yield of 1° amine due to multiple substitution.

How would you maximise the yield of the primary amine?

Use excess ammonia.

What type of mechanism is the reaction of a haloalkane with a cyanide ion?

Nucleophilic substitution

What conditions does this reaction require? What is the product formed?

Ethanol as a solvent. A nitrile is formed.

How do you get from a nitrile to a primary amine? (name of reaction type and reagents/catalysts).

Reduction using Nickel / Hydrogen catalyst.

Why is this a purer method of synthesising amines?

Only the primary amine can be formed.

What conditions are needed to form nitrobenzene from benzene?

Concentrated H2SO4 and HNO3 to form the NO2+ ion for electrophilic attack.

How do you form an ammonium chloride salt from nitrobenzene? What conditions are needed?

Reduce the nitrile using Tin / HCl → forms an ammonium salt with Cl - ions Room temperature

Equation for the reaction of nitrobenzene → phenylamine.

C6H5NO2 + 6[H] → C6H5NH 2 + 2H2O

What mechanism is used for forming amides from acyl chlorides and amines?

Nucleophilic addition/elimination.