3.11 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 IMF do they have and why
Hydrogen bonding due to polar N-H bond and lone pair of electrons on N atom
Do amines have imf which are stronger than or weaker than alcohols? Why?
Weaker, as N has a lower electronegativity than O —> weaker hydrogen bonding
What state are amines at 298K
Short chains are gases, longer chains are volatile liquids
What do they smell of, why
Fishy smell - rotting fish/flesh releases di- and triamines
Which primary amines are soluble in water/alcohols why
Up to 4 carbon atoms, as they can hydrogen bond to water molecules. After this, non-polarity of hydrocarbon chains makes them insoluble
What kind of solvents are most other amines soluble in
Less or non-polar solvents
Solubility of phenylamine, why
Not very soluble due to the non-polarity of the benzene ring - C6H5 cannot form hydrogen bonds
How can/when do amines act as bases
When they bond with a H+ ion
How can/when do amines act as nucleophiles
When they bond with an electron deficient C atom (donate lone pair from N)
Draw a mechanism for the basic action of an amine with water
What is the product from the basic action of an amine with water
RNH3+ ammonium ion, which forms a salt with an anion
Is ammonium ion soluble in water
Yes as its ionic so attracted to the polar bonds in H2O
How could you regenerate the soluble amine from the ammonium salt
Add a strong base (NaOH) –> removes H+ ions from ammonium ion
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 does positive/negative inductive effect mean
Positive inductive effect = donate electrons, increase density around N
Negative means remove electrons, decrease density around N
What effect do alkyl groups have on electron density and base strength
Positive inductive effect - increase electron density around N - stronger base
What effect do aryl groups have on electron density and base strength
Negative inductive effect - decrease electron density around N - weaker base
Why are tertiary amines never good bases
Insoluble in water
Draw a mechanism for the nucleophilic substitution of NH3 with RCH2Br to form primary amines
How can primary amines then form secondary, tertiary etc
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 primary amine due to multiple substitutions
How do you get from a nitrile to a primary amine (name of reaction type and reagents/catalysts)
Reduction using Nickel / hydrogen catalyst
What mechanism is used for forming amides from acyl chlorides and amines
Nucleophilic addition / elimination
Draw a mechanism for the reaction of ethanoyl chloride with ethanamine
