A2- Amines
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What is a primary amine?
an amine group bonded to 2 hydrogens and 1 alkyl group
What is a secondary amine?
an amine group bonded to 1 hydrogens and 2 alkyl group
What is a tertiary amine?
an amine group bonded to 3 alkyl group
Why can amines act as bases?
have a lone pair that is able to accept a proton (donate its lone pair)
How do you name amines?
1- find parent chain 2- name other groups bonded to Nitrogen, with N infront 3- write groups in alphabetical order and add amine
Why are straight chain amines stronger bases than ammonia?
• positive inductive effect pushes electron density towards lone pair • lone pair is more available to be donated to a proton
Which of the following is a stronger base, a primary amine or a tertiary amine? Why?
• tertiary • greater positive inductive effect • lone pair is more available to be donated to a H
Why are aromatic amines weaker bases than ammonia?
• lone pair is pulled into the delocalised electron system • lone pair is less available to be donated to a proton
How are amines formed through substitution of halogenoalkanes?
react a halogenoalkane with excess NH3, dissolved in ethanol
What would happen if there was an excess of halogenoalkane in a substitution with ammonia?
reaction will not stop and will form a secondary or tertiary amine
How can amines be formed?
• reduction of nitriles • substitution with halogenoalkanes • reduction of nitroarenes
What reactant is used to reduce nitriles?
LiAlH4 (lithium aluminium hydrides) dissolved in ether
Why is LiAlH4 dissolved in ether and not water?
the presence of water will cause an alcohol to form
What 2 steps are involved in forming an amine through reduction? What amines are formed?
1) form RCN 2) reduced to PRIMARY amine using Ni/H2 catalyst
What is the overall equation showing the reduction of nitroarenes?
C6H5NO2 + 6[H] -> C6H5NH2 + 2H2O
What reactants are used to reduce nitroarenes?
concentrated HCl and Sn catalyst
What temperature is needed to reduce nitroarenes?
room temp
What are cationic surfactants?
quaternary ammonium salts that have a long hydrocarbon tail
How do cationic surfactants act as washing up liquids?
nonpolar tail attracted to grease polar head attracted to water allows oil to mix with water
What else is produced from reacting a halogenoalkane with excess ammonia?
secondary, tertiary and quaternary salts
What is catalytic hydrogenation?
the use of a nickel or Pt catalyst and hydrogen gas to reduce nitriles
What are aliphatic amines?
R is an alkyl groups
Why is NaOH needed in the reduction of nitroarenes?
proton acceptor
What are surfactants?
chemicals that lower the surface tension between immiscible liquids and allow wetting to take place