amines Flashcards

1
Q

what are amines?

A

compounds based on ammonia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is a primary amine?

A

when one of the hydrogens on the ammonia has been replaced by an alkyl group

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is a secondary amine?

A

when two of the hydrogens on the ammonia molecule have been replaced by alkyl groups

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is a tertiary amine?

A

when all three of the hydrogens on the ammonia have been replaced by alkyl groups

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is a quarternary ammonium compound?

A

formed from a tertiary amine where the lone pair on the hydrogen forms a coordinate bond to another alkyl group

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

why are small amines soluble?

A

they can form hydrogen bonds with water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

how do small tertiary amines form h bonds with water?

A

the lone pair on the nitrogen forms h bond to the delta positive on the hydrogen on the oxygen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

explain the relationship between solubility and length of hydrocarbon chain?

A

less soluble as hydrocarbon chain increases bc hydrocarbon chain has to force its way between water molecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

how can you make a primary amine?

A

halogenoalkane and ammonia

reduction with a nitrile

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

explain how primary amines can be made from halogenoalkanes

A

heat halogenoalkane and excess conc ammonia in ethanol in a sealed test tube

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

name the mechanism of the production of a primary amine from a halogenoalkane?

A

nucleophilic substitution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

why can ammonia act as a nucleophile?

A

has a lone pair on the nitrogen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

why does further substitution happen when a primary amine is made?

A

because the primary amine has a lone pair on the nitrogen so it can act as a nucleophile and react with the halogenoalkane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is the major product when excess ammonia is used

A

primary amine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is the major product when excess halogenoalkane is used?

A

quarternary amine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

give some of the uses of quarternary ammonium salts

A

cationic surfactants which are found in detergents, fabric softeners and conditioners

17
Q

give the reagents and conditions for the reduction of a nitrile to form an amine

A

ethanolic KCN
with hydrogen
nickel catalyst
OR a reducing agent eg. lithium tetrahydridoaluminate IN ETHER

18
Q

give the equation of a nitrile being reduced

A

R-CN + 2H2 (or 4[H])—-> RCH2NH2

19
Q

by what process is phenylamine made

A

reduction of nitrobenzene

20
Q

give the equation of the reaction of nitrobenzene

A

RNO2 + 6[H] —-> RNH2 + 2H2O

21
Q

give the conditions for the reduction of nitrobenzene

A

heat under reflux
in the presence of a tin catalyst
conc HCl
conc NaOH

22
Q

why do you use a sealed test tube when making a primary amine?

A

so that the ammonia gas doesn’t escape

23
Q

give the two stages of the reaction of ammonia with halogenoalkane

A

NH3 + R-X —> RNH3+X-

RNH3+X- + NH3 —-> RNH2 + NH4X

24
Q

in the reduction of nitrobenzene, why is conc NaOH added?

A

because adding the acid gives the protonated form of the benzene. The NaOH removes the H+ to form water/

25
what are the uses of aromatic amines?
manufacture of dyes
26
what is a base?
a proton acceptor
27
why can ammonia and amines act as bases?
they have a lone pair on the nitrogen which can form a coordinate bond to protons
28
ammonia + acid --->
ammonium salt
29
amine + acid ---->
alkyl ammonium salt
30
give an equation and explain how it shows that amines are weakly basic
RNH2 + H2O ----> RNH3+ + OH- equilibrium lies to the left bc the amines only partially dissociate so the solution is only partially basic
31
what does the strength of a base depend on?
the availability of the lone pair
32
why are tertiary amines the strongest base?
because they have the most alkyl groups which have positive inductive effect so the lone pair is most available
33
why are aromatic amines the weakest base?
because the lone pair overlaps with the delocalised pi system so the lp is delocalised into it. the lp isnt readily available for
34
what is a disadvantage of using the nitrile method to make amines?
toxic KCN gas produced
35
what is a disadvantage of using the halogenoalkane method to make amines?
further substitution happens so more than one product so lower yield
36
how could you distinguish between samples of aqueous ammonia and amines?
use a pH meter | ammonia has a lower pH than amine