Amines

Question 1

What is an aryl group?

Answer 1

a benzene ring

Question 2

Difference between primary/secondary/tertiary amines?

Answer 2

number of H attached to the N

Question 3

How do you name simple amines?

Answer 3

if more than one place the amine group could go - add number-amino(chemical)
ethylamine
2-aminopropane
phenylamine

Question 4

How do you name secondary amines?

Answer 4

N- (what H was replaced with) amino - rest of molecule
N-methylaminoethane

Question 5

How do you name tertiary amines?

Answer 5

N,N- dimethylaminomethane

Question 6

What can amines behave as?

Answer 6

bases/nucleophiles/ligands

Question 7

When amines act as bases…

Answer 7

the lone pair is donated to a proton

Question 8

When amines act as nucleophiles…

Answer 8

the lone pair is donated to an electron deficient carbon

Question 9

When amines act as ligands…

Answer 9

the lone pair is donated to a transition metal ion

Question 10

How are dative bonds shown when the amine acts as a bronsted-lowry base?

Answer 10

–> solid arrow from N to H+

Question 11

What do amines react with acids to make? eg- CH3NH2 + HCl

Answer 11

soluble salts - CH3N+H3Cl- (methylammonium chloride)

Question 12

Amines in water make…

Answer 12

an alkaline solution

Question 13

What does the strength of amines as a base depend on?

Answer 13

the availability of the lone pair on the nitrogen for protonation (stronger bases, more availability)

Question 14

What is the relationship between alkyl groups and the availability of the lone pair?

Answer 14

alkyl groups push the electrons onto the attached group, meaning they are electron releasing, which increases the availability of the lone pair. longer alkyl chain length = more available

Question 15

Order these in terms of strongest to weakest base:
methylamine
ammonia
ethylamine
phenylamine

Answer 15

ethylamine
methylamine 1<2<3, as more alkyl groups
ammonia
phenylamine

Question 16

Why are aromatic amines weaker bases than ammonia?

Answer 16

the lone pair gets involved in delocalisation stabilisation, drawing away from the attached group

Question 17

How to find pKa?

Answer 17

-log (Ka)

Question 18

How to compare relative base strengths of amines?

Answer 18

stronger bases have higher pKa values

Question 19

Which mechanisms have amines reacting as nucleophiles?

Answer 19

-nucleophilic substitution
-nucleophilic addition-elimination

Question 20

What can happen after NH3 and a haloalkane react?

Answer 20

the primary amine formed have a lone pair of electrons on the N that can also react with another haloalkane, forming a secondary amine. the secondary amine can then go on to react with another to form a tertiary amine. it can then happen AGAIN to form a quaternary ammonium salt

Question 21

Why can a quaternary ammonium salt not act as a nucleophile?

Answer 21

no lone pair

Question 22

How do you reduce the chance of further substitution?

Answer 22

large excess of ammonia used, would give a better yield of the primary amine

Question 23

How is a high yield of a quaternary ammonium salt achieved?

Answer 23

large excess of haloalkane

Question 24

What is a use for quaternary ammonium salts?

Answer 24

cationic surfactants in fabric conditioners/hair products- -reduce the static due to negatively charged electrons

Question 25

What are amines used for?

Answer 25

to make polymers like polyamides (nylon fibres for clothes/carpets) and drugs like painkillers and polyurethanes (cavity wall insulation)

Question 26

How can you make primary aliphatic amines?

Answer 26

-2 step synthesis:
-make a nitrile through a nucleophilic substitution (+:CN-)
-reduction to a primary amine by catalytic hydrogenation (2H2/Ni/150C)

ie- butanenitrile –> 1-aminobutane

Question 27

Why can’t we use catalytic hydrogenation when there is a ketone group?

Answer 27

would reduce it to a 2ndary alcohol

Question 28

Why will metal/acid combinations NOT reduce a ketone?

Answer 28

they are weaker reducing agents