Amines Flashcards
How so 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 the 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 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
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
Place the following in order of base strength: NH3, 1 amine, 2 amine, phenylamine
2 amine > 1 amine > NH3 > phenylamine
How can primary amines then form 2, 3 amines and 4 ammonium ions?
multiple substitutions; primary amines is a nucleophile that attacks the original haloalkane etc
What are the problems with the method of multiple substitutions?
Not efficient as low yield of primary amine due to multiple substitutions.
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 product is formed?
Ethanol as a solvent
A nitrile is formed
How do you get from a nitrile to a primary amine?
Reduction using Nickel/ hydrogen catalyst
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
What mechanism is used for forming amides from acyl chlorides and amines?
Nucleophilic addition/ elimination
