CH28 Amines Flashcards
Naming amines
-amine
amino-
Why are amines so reactive
Lone pair of electrons on N
Polar N-H bond
Shape and bond angle of amines
Trigonal pyramidal
107 degrees due to lone pair on N
What intermolecular forces - why
H bonding - polar N-H and lone pair on N
Stronger or weaker intermolecular forces than alcohols - why
Weaker - N has lower electronegativity than O, weaker H bonding
What state are amines at 298K
Short chains - gases
Longer chains - volatile liquids
What do they smell of - why
Fishy smell - rotting fish release di / tri amines
Which primary amines are soluble in water / alcohols
Up to 4 carbon atoms - H bond to water
What kind of solvents are most other amines soluble in
Less or non-polar solvents
Solubility of phenylamine
Not very - non-polarity of benzene ring - no H bonds
When do amines act as bases
When they bond with a H+ ion
When do amines act as nucleophiles
When they bond with an electron deficient C atom
Product from basic action of an amine with water
RNH3 +
Ammonium ion which forms a salt with an anion
Is ammonium ion soluble in water - why
Yes - ionic so attracted to polar bonds in water
How could you regenerate soluble amine from ammonium salt
Add strong base (NaOH) –> removes H+ ions from ammonium ion
In order to be the strongest base what must a particular amine have
Greatest electron density around N atom making it a better electron pair donor
What is the positive inductive effect
Donates electrons - increase density around N
What is negative inductive effect
Removes electrons - decrease density around N
What effect do alkyl groups have
Positive inductive effect
Increase electron density
Stronger base
What effect do aryl groups have
Negative inductive effect
Decrease density around N
Weaker base
Why are tertiary amines never good bases
Insoluble in water
Order the base strength of:
ammonia, primary amine, secondary amine, phenylamine
secondary amine > primary amine > ammonia > phenylamine
How can primary amines form other amines
Multiple nucleophilic substitutions
Problems with this method
Not efficient as low yield of primary amine due to multiple substitutions
How would you maximise yield of primary amine
Use excess ammonia
What mechanism is the reaction of a halogenoalkane and a cyanide ion
Nucleophilic substitution
Conditions and product for that reaction
Ethanol solvent
Nitrile formed
How do you get from a nitrile to a primary amine
Reduction using Nickel / Hydrogen catalyst
Why is this a purer method of synthesising amines
Only primary amine formed
Conditions needed to form nitrobenzene from benzene
Conc H2SO4 and HNO3 to form NO2 +
How do you form an ammonium chloride salt from nitrobenzene
Reduce nitrile using Tin / HCl –> forms ammonium salt with Cl- ions
RT
Equation for reaction of nitrobenzene to phenylamine
C6H5NO2 + 6[H] –> C6H5NH2 + 2H2O
Mechanism used for forming amides from acyl chlorides and amines
Nucleophilic addition / elimination
Which industries use amines
Dyes
Nylon
Drugs
Synthesis of new molecules
What are cationic surfactants
Quaternary ammonium salts with a cation that is charged at 1 end and non-polar at the other
How do cationic surfactants work in hair conditioner
-ve charges on surface of hair attract cation
Removing them from surface
Prevents build-up of static electricity keeping kair flat
