6.2.1 Amines Flashcards
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?
Trigonal pyramidal, 107 degrees due to lone pair on N
What kind of intermolecular forces do they have? Why?
Hydrogen bonding due to polar N-H bond and long pair of electrons on N atom.
Do amines have intermolecular forces which are stronger 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)
What is the product from the basic action of an amine with water?
RNH3+ - ammonium ion, which forms a salt with an anion
Write an equation for methylamine with HCl
H3C-NH2 + HCl -> H3C-NH3+Cl-
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 eletron density and base strength)?
Positive inductive effect- increase electron density around N -> stronger base
How can primary amines then form secondary, tertiary amines and quarternary ammonium ions?
Multiple substitutions; primary amine is a nucleophile that attacks the original haloalkane etc.
What are problems with this method?
Not as efficient as low yield of primary amine due to multiple substitutions
How would you maximise yield of primary amine?
Use excess ammonia
What type of mechanism is reaction of haloalkane with a cyanide ion?
Nucleophilic substitution
What conditions does substitution of cyanide to a haloalkane need? What is product formed?
- Excess ethanol as a solvent
- A nitrile is formed
How do you get from a nitrile to a primary amine?
Reduction using nickel catalyst and hydrogen
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 NO2+ ion for electrophilic attack
How do you form an ammonium chloride salt from nitrobenzene? What conditions are needed?
Reduce the nitrate using tin/ HCl -> forms an ammonium salt with Cl- ions
Room temperature
What mechanism is used for forming amides from acyl chlorides and amines?
Nucleophilic addition/ elimination
