Amines Flashcards

1
Q

Amine

A

Organic molecule derived from ammonia: alkyl groups replace the hydrogen on NH3

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2
Q

Primary amine

A

When 1 alkyl group replaces the 1 hydrogen in NH3

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3
Q

How to name primary amines?

A

Alkyl group name (eg butyl)
Amine
2-propylamine

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4
Q

Secondary amine

A

When 2 alkyl groups replace 2 hydrogen on the NH in the molecule

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5
Q

Naming secondary amines

A

N-
(Number of carbon the NH is bonded to on short chain if necessary)-
Shorter chain alkyl group-
(Number of carbon the NH is bonded to on long chain if necessary)-
Longer chain alkyl group
Amine

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6
Q

Tertiary amines

A

Where 3 of the hydrogen are replaced by 3 alkyl groups on the NH3

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7
Q

Naming tertiary amines

A

N-
Shortest chain alkyl groups in alphabetical order (separated by -N-)
-number of carbon in the longest chain carbon is bonded to-
Longest chain alkyl
Amine

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8
Q

What bonds can primary and secondary amines form between each other?

A

(London forces and permanent dipole dipole forces)
HYDROGEN BONDS

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9
Q

Why can secondary and primary amines form H bonds to each other?

A

Because they contain hydrogen bonded to nitrogen
Nitrogen is electronegative to attract the pair of electrons in N-H to its nucleus enough so hydrogen is polarised to form H bonds to a line pair of electrons

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10
Q

What forces can tertiary amines form?

A

London forces and permanent dipole dipole forces

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11
Q

Why can tertiary amines not form hydrogen bonds to other tertiary amines?

A

Because it has no N-H bonds (all Hydrogen in the amine group is replaced with alkyl groups)

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12
Q

Why do primary and secondary amines have higher boiling points than tertiary amines?

A

Secondary and primary amines can form London forces, permanent dipole forces AND HYDROGEN BONDS
Tertiary amines can only form London forces and permanent dipole-dipole forces
So the former require more energy to overcome the hydrogen bonds between molecules

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13
Q

Amines vs corresponding alcohol: boiling point

A

O-H bond in alcohol is more polar than N-H bond in amine
So the hydrogen bond is stronger in alcohol than in the amine SO H bonds requires more energy to overcome in the alcohol so the amine has a lower boiling point
(If factor of carbon chain length is consistent across both molecules)

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14
Q

Can short chain amines (of all classifications) dissolve in water?

A

Yes

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15
Q

Why can all amines with short carbon chain dissolve in water?

A

Because hydrogen can form H bonds to lone pair of electrons on the nitrogen in ALL amines
Thus if the energy released is stronger making these h bonds than energy required to break hydrogen bonds/bonds bwteeen amines the amine can dissolve

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16
Q

Are secondary and primary amines more soluble in water?

A

Yes because they can form more hydrogen bonds to the water than a tertiary one

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17
Q

Why can long chain alkyl groups in an amine prevent dissolving in water?

A

Because the long chain alkyl groups will interfere with the hydrogen bonds between the water

18
Q

Do primary amines dissolve most in water?

A

Yes because they can form most hydrogen bonds than any other

19
Q

2 ways of synthesising a linear (aliphatic amine)

A

Halogenoalkane + ammonia
Reduction of a nitrile/amide

20
Q

Halogenoalkane + ammonia conditions

A

Excess concentrated ammonia in ethanol
Heated in a sealed tube

21
Q

Mechanism for ammonia + halogenoalkane

A

Nucleophilic substitution
Halogen is substituted for ammonia
Hydrogen is lost from ammonia (attracted to 2nd ammonia molecule)

22
Q

Products of ammonia + halogenoalkane

A

Ammonium salt (ammonium ion+halide ion-)
And a primary amine of the same length

23
Q

Reduction of a nitrile/amide conditions

A

Warm nitrile/amide and 4 LiAlH4 in dry ether
Hydrolysis with dilute acid

24
Q

Product of reduction of nitrile

A

Just the PRIMARY amine

25
Can reduction of a nitrile ever produce a secondary/tertiary amine?
No because of the way nitriles have a C triple bond N then the carbon the nitrogen is on will always only be bonded to 1 alkyl group Therefore only primary amines are possible
26
Products for reduction of an amide
The amine of the same classification And water
27
How does reduction of an amide work?
The C=O bond breaks and 2 hydrogen bond to the carbon We used 4[H] so the other 2 H form water with the lost oxygen No change is made to the nitrogen hydrogen part = form amine of same classification as amide
28
Synthesis of aromatic amines uses what molecule?
Nitro aromatic compounds eg nitrobenzene
29
First step of synthesis of aromatic amine conditions
Reflux With tin and concentrated HCl
30
First step of synthesis of aromatic amines is a…
Redox reaction
31
First step of synthesis of aromatic compounds reaction
Nitrobenzene + 6[H] + H+ ——> carbon chainNH3 +2H2O
32
Second step of synthesis of aromatic amines
Steam distillation under NaOH (aq) RNH3+ +OH- ——> RNH2 + H2O
33
How many reducing agents is needed for synthesis of aromatic amine from nitrobenzene?
6
34
Why do amines act as bases?
Because nitrogen has a lone pair of electrons that can accept a H+ from an acid
35
Amine + H+ forms (The conjugate aid)
Alkyl/Aryl ammonium ion
36
How to reform amine from an alkyl/aryl ammonium ion?
Wah through with dilute NaOH
37
Why do amines act as stronger bases than ammonia?
Inductive effect: alkyl groups can donate electrons to Nitrogen increasing its electron density thus ability to attract H+
38
Stronger the base of amine has what effect on its conjugate weak acid?
Weaker the acid: stronger attraction to H+ so harder to donate
39
Ka and pKa values of a conjugate weak acid
Larger pKa and smaller Ka for long chain amines (That act as stronger bases due to inductive effect) Smaller pKa and larger Ka for short chain amines (act as weaker bases but donate H+ easier)
40
What makes an amine act as a stronger base?
Having a longer alkyl chain Being aliphatic
41
Why do aromatic amines act as weaker bases (but stronger conjugate acids once an aryl ammonium ion)
Lone pair of electrons in nitrogen is drawn into pi system of a benzene (ring of delocalised electrons) Due to overlap of p orbitals Reduces ability to attract a H+ and act as a base