Amines

Question 1

what are amines? (2)

Answer 1

weak bases (Bronsted-Lowry)
nucleophiles

Question 2

how can primary amines be prepared?

Answer 2

by the reaction of ammonia with halogenoalkanes (nucleophilic substitution) and by the reduction of nitriles (hydrogenation)

Question 3

how are aromatic amines prepared?

Answer 3

by the reduction of nitrobenzene

Question 4

what are aromatic amines used in?

Answer 4

the manufacture of dyes

Question 5

what reactions do amines undergo?

Answer 5

nucleophilic substitution
nucleophilic addition-elimination

Question 6

what happens to ammonia for an amine to be produced?

Answer 6

at least one hydrogen is replaced by an organic group

(amines are derivatives of ammonia)

Question 7

in the nucleophilic substitution reaction to produce amines, how can only a primary amine be produced?

Answer 7

by adding ammonia in excess

Question 8

how can the products be separated in the nucleophilic substitution reaction to produce amines?

Answer 8

fractional distillation

Question 9

what conditions are needed for the reduction of nitriles?

Answer 9

LiAlH4 (reducing agent)
acidic conditions

Question 10

what conditions are needed for the reduction of nitrobenzene?

Answer 10

Sn (Tin) - catalyst
conc. HCl

Question 11

what are cationic surfactants?

Answer 11

molecules with a positive and negative end

Question 12

why are cationic surfactants good conditioners?

Answer 12

the 2 oppositely charged ends are attracted to different substances which prevents static from building up on surfaces

Question 13

why are amines bases?

Answer 13

the lone electron pair can accept protons

Question 14

what does the strength of an amine as a base depend on?

Answer 14

the availability of the lone pair

more available = more likely to accept a proton = stronger base

Question 15

how can different functional groups affect how available a lone pair is?

Answer 15

by changing the electron density around the bond

Question 16

what is a negative inductive effect?

Answer 16

draws electron density away = lone pair less available

Question 17

what is a positive inductive effect?

Answer 17

pushes electron density in = lone pair more available

Question 18

which are stronger bases, aliphatic amines or aromatic amines?

Answer 18

aliphatic amines

Question 19

are amines reactive?

Answer 19

yes they are very reactive

Question 20

what is the name of CH3–NH2?

Answer 20

methylamine

Question 21

what is the name of C2H5–NH2?

Answer 21

ethylamine

Question 22

what is the name of NH2 with a benzene ring?

Answer 22

phenyl amine

Question 23

what can the R be in RNH2 (amines)?

Answer 23

an alkyl group or an aryl group (aromatic)

Question 24

are the boiling points higher or lower of amines with comparable alcohols (e.g. methylamine and methanol)? why?

Answer 24

alcohols have higher boiling points because the O-H bond is more polar so the hydrogen bonds are stronger and so require more energy to overcome

Question 25

are amines polar or non-polar?

Answer 25

polar

Question 26

what do amines react with acids to form?

Answer 26

salts (ionic compounds)

Question 27

which are stronger bases, ammonia or primary alkyl amines?

Answer 27

primary alkyl amines

Question 28

which are stronger bases, primary alkyl amines or secondary alkyl amines? why?

Answer 28

secondary alkyl amines because they have two inductive effects (from the 2 alkyl groups)

Question 29

what do alkyl groups do in an amine?

Answer 29

release electrons away from the alkyl groups towards the nitrogen atom (positive inductive effect)

Question 30

what do aryl groups do in an amine?

Answer 30

withdraw electrons from the nitrogen atom (negative inductive effect)

Question 31

why is the preparation of amines through the reaction of ammonia with halogenoalkanes not efficient?

Answer 31

because a mixture of products is produced (1, 2, 3 amine and a quaternary ammonium salt)