CH28 Amines Flashcards
(36 cards)
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
