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A2 CHEMISTRY > Amines > Flashcards

Flashcards in Amines Deck (59):
1

Differences between primary, secondary and tertiary amines

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

2

Differences in boiling points of primary, tertiary and secondary amines

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.

3

Solubility of amines

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.

4

Smell of amines

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

5

How do amines act as bases?

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

6

Amine reactions with acids

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

7

Reaction of amines with water

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

8

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

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.

9

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

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.

10

What is an amino acid?

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

11

What is an alpha amino acid?

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

12

What is the general formula of an alpha amino acid?

RCH(NH2)COOH

13

What is a zwitterion?

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.

14

What the the isoelectric point?

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

15

How does R group affect isoelectric point? ***

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.

16

Amino acid in an environment more acidic than isoelectric point

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

17

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

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

18

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

Cl- + CH3CH(NH3+)COOH formed

19

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

Forms H2O + CH2(NH2)COO-Na+

20

What feature of amino acids allows them to form polymers?

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

21

What is condensation?

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

22

What does condensation polymerisation require?

Monomers with two different functional groups

23

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

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

24

General formula for forming a polyester with one type of monomer

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

25

General formula for the formation of a polyester from different monomer

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

26

How is terylene made?

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

27

How is polylatic acid made?

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

Uses of polyesters

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

What is an amide/peptide bond?

-C=O - NH2

30

What is the bond present in polyamides?

- C=O - NH -

31

What types of functional groups required to make polyamides?

Carboxyl and amine

32

Making a polyamide with one type of monomer

Amino acid which contains both COOH and NH2 groups is used
n H2N - B - COOH -> -[-NH - B - CO-]- n + (2n-1) H2O

33

Making a polyamide with two different monomers

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

Making Nylon - 6,6

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

Making Kevlar

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

36

Uses of polyamides

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

37

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

Polypeptides and proteins joined by peptide links

38

Acid hydrolysis of polypeptides

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

Alkaline hydrolysis of polypeptides and proteins

+ NaOH (aq) just above 100 degrees
Polypeptide or protein is broken down into amino acids in the form of their sodium salts

40

How can condensation polymers be broken down?

Acid or alkali hydrolysis

41

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

- The sodium salt of a carboxylic acid
- A hydroxyl group

42

Conditions for hydrolysis of polesters

Hot aqueous acid or alkali

43

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

The monomer units of the polyester

44

Alkali hydrolysis of terylene

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

45

Acid hydrolysis of terylene

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

46

What is formed in acid hydrolysis of polyamides?

Dicarboxylic acid and ammonium salt of the diamine

47

What is formed in alkali hydrolysis of polyamides?

Sodium salt of dicarboxylic acid and the diamine

48

Acid hydrolysis of nylon-6,6

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

49

Alkaline hydrolysis of nylon-6,6

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

50

Common property of bonds in biodegradable polymers

Chemical bonds can undergo hydrolysis

51

What are photo-degradable polymers?

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

How are photo-degradable polymers manufactured?

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

What is a chiral carbon?

A carbon atom with four different groups attached

54

How should optical isomers be drawn?

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

55

Properties of optical isomers

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

Advantages of production of a single isomer with correct pharmacological activity

Risks from undesirable side effects are reduced.
Drug doses are reduced because half the drug won't be wasted

57

Problem with synthesising chiral compounds in a lab

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

Methods to prepare single chiral isomers

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

59

Base reactions of amines

---> NH3+A-