amines

Question 1

what kind of base do amines act as

Answer 1

bronsted-lowry bases

Question 2

why are primary amines able to act as bases

Answer 2

Primary aliphatic amines act as Bronsted-Lowry Bases because the
lone pair of electrons on the nitrogen is readily available for forming a
dative covalent bond with a H+ and so accepting a proton. They are
weak bases as only a low concentration of hydroxide ions is
produced.

Question 3

why are primary amines better bases than ammonia

Answer 3

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

Question 4

why are secondary amines better bases than primary amines

Answer 4

Secondary amines are stronger bases than primary amines because they have more alkyl groups that are
substituted onto the N atom in place of H atoms. Therefore more electron density is pushed onto the N atom (as
the inductive effect of alkyl groups is greater than that of H atoms)

Question 5

why are aromatic amines weak bases

Answer 5

Primary aromatic amines such as phenylamine do not form basic solutions because the
lone pair of electrons on the nitrogen delocalise with the ring of electrons in the benzene
ring. This means the N is less able to accept protons.

Question 6

order of basic strength

Answer 6

Aromatic amines < ammonia< primary amines< secondary amines

Question 7

what is formed when amines react with acids

Answer 7

ammonium salts

Question 8

amine + acid equation using HCL and methylamine

Answer 8

CH3NH2 (aq) +HCl (aq) = CH3NH3+Cl-

aq) (methylammonium chloride

Question 9

how to convert ammonium salt back to amine

Answer 9

add NaOH

Question 10

what is true about ammonium salts and solubility

Answer 10

good solubility in water because of ionic character

Question 11

how to make primary amine in one step reaction and name mechanism, conditions, reactants and products

Answer 11

add ammonia to halogenoalkane
nucleophilic substitution reaction
ethanol dissolved

Question 12

bromoethane into primary amine equation and name

Answer 12

CH3CH2Br + 2NH3 = CH3CH2NH2 + NH4Br

bromoethane + ammonia = ethylamine

Question 13

what is the problem with nucleophilic substitution in forming primary amines

Answer 13

the product has a lone pair and thus further reactions can occur to form secondary and tertiary amines or quaternary ammonium salts

Question 14

how to make yield of primary amine higher in nuc sub reaction

Answer 14

Using an excess of ammonia can limit the further
subsequent reactions and will maximise the amount
of primary amine

Question 15

how to promote the formation of quaternary ammonium salt from nuc sub reaction

Answer 15

use excess halogenoalkane

Question 16

use of quaternary salt and why

Answer 16

cationic surfactants
reduce surface tension of liquids
The positive nitrogen is attracted toward negatively
charged surfaces such as glass, hair, fibres and plastics.
This helps in their uses as fabric softeners, hair
conditioners and sewage flocculants

Question 17

other better way to make amines

Answer 17

reduction of nitriles

Question 18

step 1 of making amines from nitriles reagents and conditions

Answer 18

convert halogenoalkane into nitrile using KCN in ethanol and heat under reflux

Question 19

step 1 making amines from nitriles equation using bromoethane and KCN

Answer 19

CH3CH2Br + CN- = CH3CH2CN + Br -

Question 20

step 2 of making amines from nitriles reagents and conditions

Answer 20

reduce nitrile to amine

use LiAlH4 in ether OR H2 and Ni catalyst

Question 21

step 2 making amines equation using bromoethane

Answer 21

CH3CH2CN + 4[H] = CH3CH2CH2NH2

Question 22

disadvantages of making amines by reducing nitriles

Answer 22

2 step so may be lower yield and takes longer

KCN is toxic

Question 23

reagents, conditions, mechanism to form aromatic amine from nitroarine

Answer 23

Sn and HCl OR Fe and HCl
Heating
Reduction

Question 24

what must be done after reducing nitroarine to make the aromatic amine

Answer 24

add NaOH to the ammonium salt formed due to the HCl to form aromatic amine

Question 25

how else can you recude nitroarine reagents and conditions

Answer 25

catalytic hydrogenation (H2 using Ni catalyst)

Question 26

what can primary amines react with to form secondary amides and what kind of mechanism

Answer 26

acyl chlorides or acid anhydrides

nucleophilic addition elimination mechanism