6.2.1 Amines

Question 1

what are primary, secondary and tertiary amines?

Answer 1

• primary: the nitrogen is bonded to 1 carbon
• secondary: the nitrogen is bonded to 2 carbons
• tertiary: the nitrogen is bonded to a 3 carbons

Question 2

what is the amine group?

Answer 2

• primary: NH2
• secondary: NH
• tertiary: N

Question 3

how are amines named?

Answer 3

• suffix: -amine
• prefix: 1-amino-

Question 4

how do amines act as weak bases?

Answer 4

• the lone pair of electrons on the nitrogen is donated to the proton forming a dative bond

Question 5

how do amines react as weak bases?

Answer 5

• amines react with acids to produce alkylammonium salts

Question 6

what are the conditions for the formation of aliphatic amines?

Answer 6

• haloalkane reacts with excess ethanolic ammonia (dissolved in ethanol)
• heated in a sealed tube (no reflux - ammonia is too volatile)

Question 7

what is the general equation for the formation of aliphatic amines?

Answer 7

• RX + 2NH3 -> RNH2 + NH4X

Question 8

what is the mechanism for the formation of aliphatic amines?

Answer 8

• nucleophilic substitution
• see notes for mechanism

Question 9

what is the equation for the formation of an anime from chlorobutane?

Answer 9

CH3CH2CH2Cl + NH3 -> CH3CH2CH2NH2 + HCl

CH3CH2CH2NH2 + HCl -> CH3CH2CH2NH3+Cl-

CH3CH2CH2NH3+Cl- + NH3 -> CH3CH2CH2NH2 + NH4Cl

Question 10

what is the problem with this method for the formation of amines?

Answer 10

• it is difficult to stop this reaction at the primary amine and this can go onto form secondary and tertiary amines
• excess ammonia is used to minimise further substitution

Question 11

what are the conditions for the preparation of aromatic amines?

Answer 11

• react nitrobenzene with tin and concentrated HCl - reducing agent [H]
• heat under reflux
• followed by neutralisation with NaOH

Question 12

what is the equation for the formation of aromatic amines?

Answer 12

• C6H5NO2 + 6[H] -> C6H5NH2 + 2H2O
• see notes for diagram