10 Amines

Question 1

Define ‘amine.’

Answer 1

organic derivative of ammonia in which one or more hydrogen atom is replaced with alkyl or aromatic groups

Question 2

What makes amines both basic and nucleophilic?

Answer 2

the nitrogen atom with a lone pair of electrons on the ammonia group

Question 3

What do amines occur in?

Answer 3

both plants and animals

Question 4

State 3 examples of amines and identify them as primary or secondary.

Answer 4

NH₃ (primary)
CH₃NH₂ (secondary)
CH₃NHH₃C (secondary)

(see document for full structures)

Question 5

Draw and name two examples of neurotransmitters which are amines and state their role.

(i.e. found in the brain)

Answer 5

dopamine (double-ringed) and serotonin
an essential role in brain chemistry
(see document for structures)

Question 6

Draw and name an example of a hormone which is an amine and state its role.

(Hint = can we go back to…)
(Hint for structure = 3x the normal needed for response)

Answer 6

adrenaline (now called epinephrine)
triggers fight-or-flight response to stress
(see document for structures )

Question 7

Draw and name four examples of alkaloids which are amines and state their roles and state the R-groups differ between two of them.

(Hint = 2 heavy pain-relief drugs and 2 available OTC & in shops)

(Hint = one found in drink with 2Os)

Answer 7

morphine and codeine
For morphine R = H and for codeine R = CH₃
plant products used as synthetic drugs 
nicotine and caffeine 
act as stimulants 
(see document for structures)

Question 8

Describe the bonding in a nitrogen atom and state what it is similar to using a diagram.

(Hint: 3 bonds)

Answer 8

3 single bonds and 1 lone pair
bonding in N is similar to that in ammonia
(see document for diagram)

Question 9

Describe the bonding in aliphatic amines.

Answer 9

N is sp3 hybridised

C-N σ-bond is formed by the overlap of nitrogen sp3 and carbon sp3 orbitals

Question 10

What is the C=N=C bond angle? (Hint: tetrahedral angle with further repulsion)

Answer 10

~ 107°

Question 11

Describe the bonding in aromatic amines using a diagram.

Hint: benzene and 2 p-orbitals and 2 bonds

Answer 11

N is sp2 hybridised
lone pair occupies the p-orbital and is delocalised
(see document for diagram)

Question 12

State, through definitions, how an amine is classified as:

a) primary (1°)
b) secondary (2°)
c) tertiary (3°)

Answer 12

a) one alkyl/aryl group is bonded to the nitrogen atom
b) two alkyl/aryl groups as substituents
c) three alkyl/aryl groups as substituents

Question 13

Draw and classify as 1°, 2° or 3°:

a) trimethylamine
b) methylamine
c) dimethylamine

Answer 13

a) 3°
b) 1°
c) 2°
(see document for diagrams)

Question 14

State the general IUPAC process of naming amines.

Answer 14

amines are named as alkanamines

the -e in alkane name of the largest chain is changed to amine

Question 15

State the IUPAC process of naming secondary amines.

Answer 15

the longest carbon chain names the amine

the other alkyl groups are listed in alphabetical order as prefixes as N-alkyl groups

Question 16

What are the common names of amines and how often are they used?

Answer 16

non-standard names are used more frequently than IUPAC

e.g. alkylamine, not alkaneamine; aniline not phenylalanine

Question 17

For longer alkyl chains or more complex molecules, which prefix is used and what for?

Answer 17

the prefix amino-

to indicate the functional group

Question 18

For the following primary amines state the IUPAC name, the common name and draw the structures:

a) CH₃CH₂CH₂NH₂CH₃
b) CH₃CH₂CH₂CH₂CH(NH₂)CH₃

Answer 18

a) (3C alkane = propanone)
IUPAC name = propanamine
Common name = N-propylamine
b) 
IUPAC name  = hexan-2-amine
Common name = 2-amino hexane 
(see document for drawings)

Question 19

Name the amine shown on the document in stages.

Answer 19

1 - find the longest chain and identify the corresponding alkane. Generate the amine name = propanamine
2 - identify the smaller alkyl groups attached to the nitrogen = methyl, ethyl
prefix the amine name with the names of the smaller alkyl groups listed in alphabetical order, each prefixed with N

You get N-ethyl-N-methyl-propanamine

Question 20

In terms of physical properties, how soluble are amines and why?

Answer 20

low molecular weight, amines are generally soluble

also soluble in organic solvents

Question 21

In terms of physical properties, what are the general boiling points of amines and why?

Answer 21

boiling points are relatively high

they are higher than alkanes but primary and secondary amines have lower boiling points than alcohols of similar mass

Question 22

In terms of physical properties, what are the characteristic odours of some amines and why?

Answer 22

some low molecular weight amines have sharp, penetrating smells similar to ammonia
higher molecular weight amines are often found in decaying animal tissues

Question 23

Which amines are responsible for the smell of rotting fish?

Answer 23

low molecular-weight amines

Question 24

Where are higher molecular weight (Mr) amines often found?

Answer 24

in decaying animal tissues

Question 25

Explain how hydrogen-bonding occurs in amines.

Answer 25

lone pair of electrons on N are hydrogen-bond acceptors | N-H bond in primary and secondary amines = H-bond donors

Question 26

How many hydrogen bonds can: a) a primary amine form b) a secondary amine form c) a tertiary amine form

Answer 26

a) up to 3 H bonds b) up to 2 H bonds c) usually form 0 H bonds

Question 27

What is the only molecule that is the exception to tertiary amines forming 0 H-bonds and why?

Answer 27

water | only water is small enough to avoid steric hindrance here

Question 28

Draw hydrogen bonds between primary, secondary amines and water molecules (including lone pairs).

Answer 28

see document

Question 29

In terms of the chemical properties of amines, what are amines a type of and how?

Answer 29

weak organic bases | accept H⁺

Question 30

Because of the chemical properties of amines what do they produce when reacted with acids or water?

Answer 30

alkylammonium salts

Question 31

Finish the following general reaction between an tertiary amine and water on the document drawing out structures with correct bond types (on document).

Answer 31

see document for answer

Question 32

How are salts of amines named?

Answer 32

salts of amines are named by changing "amine" to "ammonium"

Question 33

Name the salt formed when trimethylamine reacts with water.

Answer 33

trimethylammonium hydroxide

Question 34

In terms of chemical properties, what does the formation of salts change?

Answer 34

change solubility, stability and crystallisation

Question 35

How can the change in chemical properties during the formation of salts be used?

Answer 35

in pharmaceutical calculations

Question 36

What is adderall and what is it made up of? ASSS

Answer 36

``` CNS stimulant used in the treatment of attention deficit hyperactivity disorder and narcolepsy 25% Amphetamine aspartate monohydrate 25% Amphetamine sulfate 25% Dextroamphetamine sulfate 25% Dextroamphetamine saccharate ```

Question 37

Draw out the chemical structure of Adderall.

Answer 37

see document for this

Question 38

State how primary amines are chemically synthesised by 'reduction of nitro compounds' including: a) reagents b) conditions c) the general reaction equation (Hint: N"O₂") (Ar = alkyl)

Answer 38

a) Ar-NO₂ b) H₂, transition metal catalyst (i.e. Ni, Pt, Pd) (Hint: N"O₂"= transiti"O"n metal catalyst) c) Ar-NO₂ → ArNH₂

Question 39

State how primary amines are chemically synthesised by 'reduction of nitriles' including: a) reagents b) conditions c) the general reaction equation (Hint = "Ni"trile compound)

Answer 39

a) RC≡N b) H₂, Ni catalyst c) RC≡N → RC-NH₂

Question 40

State how primary, secondary and tertiary amines are chemically synthesised by 'reduction of amides' including: a) reagents b) conditions c) the general reaction equation (Hint = not counted as an O)

Answer 40

a) RC=ON(R'')(R') b) LiAlH₄ c) (see document for this)

Question 41

State how primary amines are chemically synthesised by 'Hoffman degradation of amides' including: a) reagents b) conditions c) the general reaction equation

Answer 41

a) RC=ONH₂ b) KOBr c) RC=O-NH₂ → R-NH₂

Question 42

Provide the reaction for primary amines to be produced from alcohols in industry. State: a) reagents b) conditions c) the general reaction equation (draw out too)

Answer 42

a) alcohol and ammonia b) High temperature and high pressure c) ROH + NH₃ → R-NH₂ + H₂O (see document for diagrams)

Question 43

In the lab, what can alkyl halides be used as and how often are they used synthetically?

Answer 43

an alkylating agent | not often used synthetically, as the reaction is difficult to control

Question 44

Draw out the general reaction equation for alkylamines production from an alkyl halide.

Answer 44

see document for this

Question 45

Describe the properties of the lone pair of electrons ammonia molecule and explain why they are present. (Hint: charge on N atom)

Answer 45

electron-rich/basic: electron-pair donor H⁺ acceptor nucleophilic (-): react with centres of positive charge

Question 46

Provide the reaction for 'condensation' with carbonyls. State: a) reagents b) the general reaction equation (draw out too) c) state the functional group created d) state the type of base created

Answer 46

a) NH₃ b) R(R')C=O → R(R')=NH (see document for diagram) c) imine (=NH) d) schiff base (with imine group)

Question 47

Provide the reaction for 'reductive amination' of carbonyls. State: a) reagents b) the 3 different types of conditions c) the general reaction equation (draw out too) (Hint: carb"O"nyls)

Answer 47

``` a) NH₃, H₂ OR NaBH₃CN OR NaBH(OAc)₃ b) transition metal catalyst c) R(R')C=O → R₂C-NH₂ ```

Question 48

What is the chemical importance of reductive amination of aldehydes/ketones?

Answer 48

synthesis of primary, secondary and tertiary amines

Question 49

State the biological importance of condensation with carbonyls in nitrogen metabolism drawing out the multi-stage example including enzymes.

Answer 49

NH₄⁺ + α-ketoglutarate + amino acid (NADPH₂, glutamate dehydrogenase) → glutamate (NH₃, ATP, glutamine synthetase) → glutamine (see document for structures)

Question 50

State the biological importance of condensation with carbonyls in the transfer of NH₂ groups drawing out the example including enzymes.

Answer 50

glutamate + keto-acid → α-keto glutarate + amino acid (aminotransferase) (see document for structures)

Question 51

State the biological importance of condensation with carbonyls in enzyme mechanisms drawing out the example including enzymes.

Answer 51

pyridoxal phosphate-dependent enznymes, photosynthesis pyridoxal phosphate → enzyme (see document for structures)

Question 52

State the products of the following general 'acid-base' reaction and state what the amine group acts as. (draw out on document too) RR'R"N: + H-A ⇌ (Hint: split reagents 2 into positive and negative ions)

Answer 52

amine = base RR'R"N: + H-A ⇌ RR'R"NH⁺A- + H-A (see document for equation)

Question 53

State the products of the following general 'alkylation' reaction and state what the amine group acts as. (see document for reaction) (Hint: split reagents 2 into positive and negative ions)

Answer 53

amine = nucleophile | see document for equation

Question 54

State the products of the following general 'acylation' reaction and state what the amine group acts as. (see document for reaction): HO₂C-C(CH₃)-NH₂ + RC=OCl → (Hint: split reagents 2 into positive and negative ions)

Answer 54

amine = nucleophile | see document for equation

Question 55

Give a biological example of an 'acylation' reaction and state the enzyme involved.

Answer 55

(see document for this)

Question 56

State the general reaction for diazonium salt formation.

Answer 56

(see document for this)

Question 57

What characteristic do aliphatic diazonium salts (R= alkyl) have and how do they compare with aromatic diazonium (R = Ar) salts; what does this mean?

Answer 57

aliphatic are very unstable aromatic are more, stable thus aromatic are more useful

Question 58

Finish the following diagram for aromatic amine formation (on document)

Answer 58

see document

Question 59

What is Hoffman elimination and what is it used for?

Answer 59

used to produce an alkene and a tertiary amine from a tertiary amine used primarily as a method for the production of alkenes

Question 60

Draw out the Hoffman elimination reaction stages.

Answer 60

see document