3.3.11 Amines (A2)

Question 1

what is the functional group of an amine?

Answer 1

NH2

Question 2

how do we name amines?

Answer 2

-amine or amino-

Question 3

why are amines so reactive?

Answer 3

the lone pair of electrons on the Nitrogen - due to polar N-H bond

Question 4

what shape are amines around the N? Bond angle?

Answer 4

trigonal pyramidal, 107 degrees due to lone pair on N

Question 5

what kind of intermolecular forces do amines have? why?

Answer 5

Hydrogen bonding due to polar N-H bond and lone pair of electrons on N atom

Question 6

do amines have intermolecular forces which are stronger than or weaker than alcohols? why?

Answer 6

weaker, as N has a lower electronegativity than O –> weaker H bonding

Question 7

what state are amines at 298K?

Answer 7

short chains are gases, longer chains are volatile liquids

Question 8

what do amines smell of? why?

Answer 8

fishy smell - rotting fish/flesh releases di and tri amines

Question 9

which primary amines are soluble in water/alcohols? why?

Answer 9

up to 4 carbon atoms, as they can hydrogen bond to water molecules.
after this, non-polarity of hydrocarbon chain makes them insoluble

Question 10

what kind of solvents are most amines soluble in?

Answer 10

less or non-polar solvents

Question 11

solubility of phenylamine? why?

Answer 11

not very soluble, due to the non-polarity of the benzene ring - C6H5 cannot form hydrogen bonds

Question 12

How can/when do amines act as bases?

Answer 12

when they bond with a H+ ion

Question 13

how can/when do amines act as nucleophiles?

Answer 13

when they bond with an electron-deficient C atom (donate lone pair from N)

Question 14

what is the product from the basic action of an amine with water?

Answer 14

RNH3+ - ammonium ion, which forms a salt with an anion

Question 15

is an ammonium ion soluble in water? why?

Answer 15

yes, as it is ionic so is attracted to the polar bonds in H2O

Question 16

how could you regenerate the soluble amine from the ammonium salt?

Answer 16

add a strong base (NaOH) –> removes H+ ions from ammonium ion

Question 17

in order to be the strongest base, what must a particular amine have (out of a set of amines)?

Answer 17

Greatest electron density around the N atom, making it a better electron pair donor (attracts protons more)

Question 18

what does positive/negative inductive effect mean?

Answer 18

positive inductive effect = donate electrons, increase density around N
negative means remove electrons, decrease density around N

Question 19

what effect do alkyl groups have (on electron density and base strength)?

Answer 19

positive inductive effect - increase electron density around N –> stronger base

Question 20

what effect do aryl groups have (on electron density and base strength)?

Answer 20

Negative inductive effect - decrease electron density around N –> weaker base

Question 21

why are tertiary amines never good bases?

Answer 21

they are insoluble in water

Question 22

place these in order of base strength in general: NH3, primary amine, secondary amine, tertiary amine

Answer 22

secondary amine > primary amine > NH3 > phenylamine

Question 23

how do primary amines then form secondary, tertiary amines and quaternary ammonium ions?

Answer 23

multiple substitutions; primary amine is a nucleophile that attacks the original haloalkane etc

Question 24

what is the problem with multiple substitutions to form secondary, tertiary amines and ammonium ions?

Answer 24

not efficient as low yield of primary amine due to multiple substitutions

Question 25

how would you maximise the yield of primary amine?

Answer 25

use excess ammonia

Question 26

what type of mechanism is the reaction of a haloalkane with a cyanide ion?

Answer 26

nucleophilic substitution

Question 27

what conditions does the reaction of a haloalkane with a cyanide ion require? what product is formed?

Answer 27

ethanol as a solvent a nitrile is formed

Question 28

how do we get from a nitrile to a primary amine? (name of reaction type and reagents/catalysts)

Answer 28

reduction using Nickel / Hydrogen catalyst

Question 29

why is the reduction using Nickel/Hydrogen catalyst a purer method of synthesising amines?

Answer 29

only the primary amine can be formed

Question 30

what conditions are needed to form nitrobenzene from benzene?

Answer 30

conc. H2SO4 and HNO3 to form the NO2+ ion for electrophilic attack

Question 31

how do you form an ammonium chloride salt from nitrobenzene? what conditions are needed?

Answer 31

reduce the nitrile using Tin/HCl --> forms an ammonium salt with Cl- ions room temperature

Question 32

what is the equation for the reaction of nitrobenzene --> phenylamine?

Answer 32

C6H5NO2 + 6[H] --> C6H5NH2 + 2H2O

Question 33

what mechanism is used for forming amides from acyl chlorides and amines?

Answer 33

nucleophilic addition/elimination

Question 34

in which industries/products are amines used?

Answer 34

dyes, nylon, drugs, synthesis of new molecules

Question 35

what are cationic surfactants (used in fabric/hair conditioners)?

Answer 35

quaternary ammonium salts, with a cation that is charged at one end (N+) and non-polar at the other

Question 36

how do cationic surfactants work in fabric/hair?

Answer 36

Negative charges on the surface of the fabric/hair are attracted to the cation, removing them from the surface; prevents build-up of static electricity and keeps hair flat and fabric smooth

Question 37

how do cationic surfactants sit when placed in water?

Answer 37

charged end in the water, non-polar end sticking out of the water/at the surface