6.2.1 Amines

Question 1

naming amines (including how the exam board name them)

Answer 1

end in -amine

but exam board may end the stem in -yl e.g. propylamine

Question 2

what happens if another priority group on the amine

Answer 2

the prefix amino is used e.g. 2-aminopropanoic acid

Question 3

what happens if amine is secondary

Answer 3

has 2 alkyl groups attached then each chain is named and the smaller alkyl group is preceded by an -N which plays the same role as a number in normal naming
e.g. N-methylpropylamine

Question 4

what happens if the chain lengths are the same size when naming an amine

Answer 4

then an N isn’t used

will use Di___amine

Question 5

what happens if amine is tertiary

Answer 5

each alkyl side group will be given an N

Question 6

what do primary aliphatic amines act as

Answer 6

bronsted-lowry bases

Question 7

how do primary aliphatic amines act as bronsted-lowry bases

Answer 7

as lone pair of electrons on the nitrogen is readily available for forming a dative covalent bond with a H+ and so accepting a proton

Question 8

strength of primary aliphatic amines

Answer 8

stronger bases than ammonia as the alkyl groups are electron releasing and push electrons towards the nitrogen atom and make it a stronger base

Question 9

base strength of aromatic amines

Answer 9

primary aromatic amines such as phenylamines don’t form basic solutions because the lone pair of electrons on the nitrogen delocalise with the ring of electrons in the benzene ring
means the N is less able to accept protons

Question 10

reactions with acids

Answer 10

amines as bases react with acids to form ammonium salts

e.g. CH3NH2 + HCl -> CH3NH3+Cl-

ionic salts will be crystals if the water is evaporated due to strong ionic interactions
the salt formed shows that compounds are soluble in the acid

Question 11

how can primary amines be formed

Answer 11

nucleophilic substitution reaction between haloalkanes and ammonia

Question 12

reaction with ammonia to form a primary amine

Answer 12

reagent: excess ammonia dissolved in ethanol (excess will prevent further substitution and maximise the amount of primary amine formed)

mechanism:

1. NH3 nucleophile attacks haloalkane, line from lone pair on NH3 to C then line from C-halogen bond to the halogen then NH3+ is found on the alkane and Br- as a separate product
2. 2nd ammonia nucleophile removes H+ from intermediate to form amine and NH4 (halogen) as a second product

Question 13

reacting primary amines with haloalkanes to form secondary amines

Answer 13

amines will react in the same nucleophilic substitution with a haloalkane to form a secondary amine

Question 14

reacting secondary amines with haloalkanes to form tertiary amines

Answer 14

same as primary to secondary

Question 15

reducing nitroarenes to aromatic amines

Answer 15

reagent: Sn and conc HCl
conditions: heating
mechanism: reduction

will require 6 reducing agents, NO2 changes to NH2 and by product of water

as reaction is carried out in HCl the salt C6H5NH3+Cl- will be formed, reducing with NaOH will give phenylamine