amines Flashcards
how many carbons does a primary amine have
1
how many carbons does a secondary amine have
2
how many carbons does a tertiary amine have
3
how many carbons does a quaternary amine have
4
how do you name amines?
-amine
or
amino-
explain the reactivity of amines
- amines are highly reactive
- because the lone pair of electrons on the nitrogen
- due to polar N-H bond
explain what shape are amines around the nitrogen? bond angle?
- trigonal pyramidal
- 107
- due to lone pair on N
what kind of intermolecular forces do amines have? why?
- hydrogen bonding due to polar N-H bond and lone pair of electrons on nitrogen atom
do amines have intermolecular forces which are stronger or weaker than alcohols? why?
- weaker
- as nitrogen has a lower electronegativity than oxygen
- forms weaker hydrogen bonds
how can/when do amines act as weak bases
the lone pair on the nitrogen accepts a proton
how can/when do amines act as nucleophiles
when they bond with an electron-deficient carbon atom and donate a lone pair from nitrogen
what is the product from the basic action of an amine with water?
RNH3+ (an ammonium ion which forms a salt with an anion)
write an equation for methylamine reacting with HCl
CH3NH2 + HCl → CH3NH3 + 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 nitrogen atom
- making it a better electron-pair donor
- so it attracts protons more
what effect do alkyl groups have on electron density and base strength of amines
- positive inductive effect
- increase electron density around nitrogen
- stronger base
place the following in order of base strength:
ammonia, primary amine, secondary amine, phenylamine
strongest to weakest
- secondary amine
- primary amine
- ammonia
- phenylamine (the lone pair on the nitrogen atom is less available)
how do you form a secondary/tertiary amine
react a primary amine with a halogenalkane
then react the salt formed with NaOH
how would you maximise the yield of the primary amine?
use excess ammonia because it reduces further substitutions of the amine groups into secondary/tertiary amines
what type of mechanism is the reaction of a haloalkane with a cyanide ion?
nucleophilic substitution
what conditions does the formation of aliphatic amines require?
- ammonia in excess
- ethanol as a solvent
how do you get from a nitrile to a primary amine? (name of reaction type and reagents/catalysts)
- reduction using nickel
- hydrogen catalyst
why is the use of nitriles a purer method of synthesising amines?
only the primary amine can be formed
what are the disadvantages of making aliphatic amines?
- produces impure products because secondary, tertiary amines are also made due to the fact that primary amines have a lone pair of electrons on the nitrogen so it acs as a nucleophile
describe a method of making aromatic amines
- reflux nitrobenzene with concentrated HCl and tin to form a salt
- react the salt with NaOH to produce aromatic amine
what conditions are needed for the formation of nitrobenzene from benzene
- concentrated H2SO4
- HNO3 to form 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 to form an ammonium salt with Cl- ions
- conduct at room temperature
equation for the reaction of
nitrobenzene -> phenylamine
C6H5NO2 + 6[H] -> C6H5NH2 + 2H2O
What mechanism is used for forming amides from acyl chlorides and amines
nucleophilic addition
how to prepare aliphatic primary amines?
- substitution of haloalkanes with excess ethanolic ammonia under reflux
- react with NaOH afterwards
mechanism in words for preparation of primary amines
- lone pair of electrons in ammonia attracted to partially positive carbon in haloalkane
- carbon halogen bond breaks
- carbon forms bond with nitrogen in ammonia
- nitrogen is positively charged
- halogen donates lone pair of electrons to hydrogen attached to nitrogen
- one nitrogen hydrogen bond breaks
