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A2 CHEMISTRY > Amines > Flashcards

Amines Flashcards

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1
Q

Differences between primary, secondary and tertiary amines

A

Primary: 1 carbon chain attached to nitrogen
Secondary: 2 carbon chains attached to nitrogen
Tertiary: 3 carbon chains attached to nitrogen

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2
Q

Differences in boiling points of primary, tertiary and secondary amines

A

Primary amines have higher boiling points as they can form hydrogen bonds with each other as well as van der Waals’ and permanent dipole-dipole interactions.
Secondary amines can also form hydrogen bonds but with the amine in the middle of the chain, the permanent dipole is less.
Tertiary amines cannot form hydrogen bonds with each other as there are no hydrogen atoms attached directly to the nitrogen.

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3
Q

Solubility of amines

A

All of the amines can form hydrogen bonds with water - even the tertiary ones.

Although the tertiary amines don’t have a hydrogen atom attached to the nitrogen and so can’t form hydrogen bonds with themselves, they can form hydrogen bonds with water molecules just using the lone pair on the nitrogen.

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4
Q

Smell of amines

A

As the amines get bigger, they tend to smell more “fishy”

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5
Q

How do amines act as bases?

A

The lone pair of electrons on the nitrogen atoms can accept a proton (and form a dative covalent bond)

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6
Q

Amine reactions with acids

A

The NH2 group gains an H+ leading to NH3+ attached to negatively chrged ion, forming a salt

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7
Q

Reaction of amines with water

A

React like ammonia, an H+ is taken from water forming an NH3+ ion and an OH- ion

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8
Q

Comparison of strengths as a base of alkylamines, ammonia and primary arylamines
(Stretch and challenge)

A

Alkylamines tend to be stronger bases than ammonia because the alkyl groups are more electron donating than H atoms so there is a higher electron density around the N atoms and the lone pair of electrons. Thus, a stronger bond is formed with an H+ ion. Primary arylamines are weaker bases than ammonia or alkylamines as the lone pair becomes partly delocalised into the benzene ring and is less available to bond to an H+ ion.

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9
Q

What is one possible problem with the synthesis of alkyl amines and how can it be reduced?

A

The product has a lone pair of electrons and can react with the halogenoalkane to form hydrogen halide + organic mixture (look at p.38) can be reduced through increasing the pressure/conc. of ammonia.

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10
Q

What is an amino acid?

A

A compound containing an -NH2 group and a carboxylic acid group

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11
Q

What is an alpha amino acid?

A

An amino acid with the amino group attached to the carbon atom adjacent to the -COOH groups

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12
Q

What is the general formula of an alpha amino acid?

A

RCH(NH2)COOH

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13
Q

What is a zwitterion?

A

A dipolar ionic form of an amino acid that is formed by the donation of a hydrogen ion from the carboxyl group to the amino group. Both charges are present so there is no overall charge.

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14
Q

What the the isoelectric point?

A

The pH value at which the amino acid exists as a zwitterion

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15
Q

How does R group affect isoelectric point? ***

A

If you add basic groups such as NH2 to the R side chain, there’s a greater chance of protonation at any given pH as there are now two proton acceptors in the amino acid. As a result, the pH needs to be higher to prevent any charges arising from protonation, hence the isoelectric point is higher.

If you add acidic groups such as COOH to the R side chain, there’s a greater chance of deprotonation at any given pH as there are now two proton donators in the amino acid. As a result, the pH needs to be lower to prevent any charges arising from deprotonation, hence the isoelectric point is lower.

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16
Q

Amino acid in an environment more acidic than isoelectric point

A

Amino acid behaves as a base and accepts a proton from the acid, forming a positively charged ion

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17
Q

Amino acid as an acid (in more basic environment than isoelectric point)

A

Amino acid donates a proton to the base forming a negatively charged ion and water

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18
Q

Reaction of alanine (CH3CH(NH2)COOH) with HCl

A

Cl- + CH3CH(NH3+)COOH formed

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19
Q

Reaction of glycine (CH2(NH2)COOH) and NaOH

A

Forms H2O + CH2(NH2)COO-Na+

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20
Q

What feature of amino acids allows them to form polymers?

A

The contain both amine and carboxyl groups so can form peptide links

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21
Q

What is condensation?

A

A reaction in which two small molecules react together to form a larger molecule with the elimination of a small molecule such as water

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22
Q

What does condensation polymerisation require?

A

Monomers with two different functional groups

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23
Q

What is a polyester and what groups do the monomers contain?

A

A polyester is formed when monomer units which contain a carboxyl and hydroxyl group are bonded together through ester linkages

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24
Q

General formula for forming a polyester with one type of monomer

A

n HO - A - COOH (hydroxycarboxylic acid) -> -[-O-B-CO-]- n + H2O

25
Q

General formula for the formation of a polyester from different monomer

A

n HO-A-OH (diol) + n COOH- B - COOH (dicarboxylic acid) -> -[-O - A - O -CO -B -CO-]- n + (2n-1) H2O

26
Q

How is terylene made?

A

Ethane -1,2 -diol and benene -1,4- dicarboxylic acid

27
Q

How is polylatic acid made?

A

Lactic acid : HO - CH(CH3) - COOH forms a polyester
A bond forms between a hydroxyl group on one lactic acid molecule and a carboxyl group an another lactic acid molecule forming an ester linkage

28
Q

Uses of polyesters

A

Makes carpets and clothes, is a strong fibre resistant to stretching, shrinking and chemical attack but burns easily. PLA used for food and drink packaging as it is biodegradable

29
Q

What is an amide/peptide bond?

A

-C=O - NH2

30
Q

What is the bond present in polyamides?

A
  • C=O - NH -
31
Q

What types of functional groups required to make polyamides?

A

Carboxyl and amine

32
Q

Making a polyamide with one type of monomer

A

Amino acid which contains both COOH and NH2 groups is used

n H2N - B - COOH -> -[-NH - B - CO-]- n + (2n-1) H2O

33
Q

Making a polyamide with two different monomers

A

A dicarboxylic acid and a diamine are used

n H2N -A -NH2 + n COOH - B - COOH -> -[-NH-A-NH-CO-B-CO-]- n + (2n-1) H2O

34
Q

Making Nylon - 6,6

A

1,6 - diaminohexane is reacted with hexane- 1,6- dioic acid
n H2N - (CH2)6- NH2 + n COOH- (CH2)4 - COOH
n -[-HN- (CH2)6 -NH-CO-(CH2)4-CO-]- + (2n-1) H2O

35
Q

Making Kevlar

A

Benzene - 1,4- dioic acid is reacted with benzene -1,4 - diamine

36
Q

Uses of polyamides

A

Fibres in clothing, kevlar is very strong and fire resistant so used in bullet proof vests

37
Q

When amino acids join together what is the name of the structure and what link is present?

A

Polypeptides and proteins joined by peptide links

38
Q

Acid hydrolysis of polypeptides

A

Heat under reflux w. 6 mol.dm^3 HCl for 24 hours. A water molecule breaks each peptide to form a mixture of the amino acids that made up the proteins with positive charge. Polypeptide + H2O + nH+ (from the acid)

39
Q

Alkaline hydrolysis of polypeptides and proteins

A

+ NaOH (aq) just above 100 degrees

Polypeptide or protein is broken down into amino acids in the form of their sodium salts

40
Q

How can condensation polymers be broken down?

A

Acid or alkali hydrolysis

41
Q

What is each ester linkage hydrolysed to during alkaline hydrolysis of polyesters

A
  • The sodium salt of a carboxylic acid

- A hydroxyl group

42
Q

Conditions for hydrolysis of polesters

A

Hot aqueous acid or alkali

43
Q

What is each ester linkage hydrolysed to during acid hydrolysis of polyesters

A

The monomer units of the polyester

44
Q

Alkali hydrolysis of terylene

A

Broken down into +Na-OOC-(O)-COO-Na+ and CH2OHCH2OH

45
Q

Acid hydrolysis of terylene

A

Broken down into Benzene -1,4- dioic acid and Ethane-1,2-diol

46
Q

What is formed in acid hydrolysis of polyamides?

A

Dicarboxylic acid and ammonium salt of the diamine

47
Q

What is formed in alkali hydrolysis of polyamides?

A

Sodium salt of dicarboxylic acid and the diamine

48
Q

Acid hydrolysis of nylon-6,6

A

Forms n H3+N-(CH2)6-N+H3 + n HOOC-(CH2)4-COOH

49
Q

Alkaline hydrolysis of nylon-6,6

A

Forms n +Na-COO-(CH2)4-COO-Na+ + H2N-(CH2)6-NH2

50
Q

Common property of bonds in biodegradable polymers

A

Chemical bonds can undergo hydrolysis

51
Q

What are photo-degradable polymers?

A

Polymers designed to become weak and brittle when exposed to sunlight for prolonged periods. They are then converted to CO2 and water in the presence of bacteria

52
Q

How are photo-degradable polymers manufactured?

A

Blending polymer with light-sensitive additives that catalyse the breakdown of the polymer when exposed to UV radiation. Or incorporating C=O bond which absorb light energy and break.

53
Q

What is a chiral carbon?

A

A carbon atom with four different groups attached

54
Q

How should optical isomers be drawn?

A

With the geometry around the chiral carbon shown as a tetrahedral shape

55
Q

Properties of optical isomers

A

They rotate plane-polarised light differently. One of the optical isomers rotates the light clockwise and the other rotates it anti-clockwise. A racemic mixture has no effect on plane-polarised light because the rotations cancel each other out.

56
Q

Advantages of production of a single isomer with correct pharmacological activity

A

Risks from undesirable side effects are reduced.

Drug doses are reduced because half the drug won’t be wasted

57
Q

Problem with synthesising chiral compounds in a lab

A

Mixture of optical isomers requires complicated separation techniques as optical isomers usually have very simillar physical or the same physical properties. Techniques include chromatography, electrophoresis and use of enzymes.

58
Q

Methods to prepare single chiral isomers

A

Using enzymes as biological catalysts
Use of transition element complexes to produce chiral catalysts
Chiral pool synthesis

59
Q

Base reactions of amines

A

—> NH3+A-

A2 CHEMISTRY (16 decks)

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