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edexcel a level chemistry > ✅17 - Organic Chemistry II > Flashcards

✅17 - Organic Chemistry II Flashcards

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1
Q

What type of isomerism is optical isomerism?

A

Stereoisomerism

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2
Q

What are structural isomers?

A

Compounds with the same molecular formula but with different structural formula

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3
Q

What are functional group isomers?

A

They differ because they have different functional groups

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4
Q

What are chain isomers?

A

Differ because they have different patterns of branching in their carbon chains

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5
Q

What are positional isomers?

A

Differ because the same functional group is attached to different carbon atoms in the chain

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6
Q

What are stereoisomers?

A

Have the same structural formula but differ because their atoms or groups are arranged differently in three dimensions

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7
Q

What are geometric isomers?

A

Differ because their atoms or groups are attached at different positions on opposite sides of a C-C double bond

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8
Q

What is chirality?

A

Two or more molecules that appear identical but cannot be superimposed onto one another.

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9
Q

What are chiral centres?

A

Carbons with four different atoms or groups attached

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10
Q

What is plane polarised light?

A

Light in which oscillations exist in planes at right angles to the direction of travel.

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11
Q

What can be used to convert unpolarised light into plane polarised light?

A

Materials such as Polaroid, which absorb all of the oscillations expect those in a single plane

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12
Q

What is polarimetry?

A

The use of a polarimeter to measure the amount of optical activity, if any, of a substance.

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13
Q

What is a monochromatic light source?

A

One of only one colour or frequency

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14
Q

What is a polariser?

A

A polarising filter that converts unpolarised light into plane polarised light

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15
Q

What happens in a polarimeter if a substance is optically active?

A

The plane of polarisation will be rotated so it is no longer vertical - Clockwise = dextrorotatory, Anticockwise = laevorotatory

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16
Q

What is the second polarising filter in a polarimeter called?

A

The analyser

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17
Q

What does the analyser do?

A

It is rotated to a position here the maximum light intensity can be seen. The angle of rotation is measured and quoted.

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18
Q

Do enantiomers have identical physical properties?

A

Yes - apart from the direction in which they rotate plane polarised light.

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19
Q

Do enantiomers have identical chemical properties?

A

Yes - apart from the way they react with enantiomers of other substances

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20
Q

What is a racemic mixture?

A

One containing equal amounts of two enantiomers.

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21
Q

What does SN2 indicate?

A

S = substitution N= nucleophillic 2=bimolecular and second order

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22
Q

What does SN1 indicate?

A

S = Substitution N = Nicleophillic 1 = unimolecular and first order

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23
Q

How can optical activity be used as evidence for SN2?

A

Because of the inversion that occurs in the SN2 mechanism, the optical activity of the product is different to that of the reactant. If the reactant is dextrorotatory, the product will be laevorotatory and vice versa.

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24
Q

How can optical activity be used as evidence for SN1 mechanisms?

A

If the reaction is via SN1, there will be no optical activity in the product.

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25
Q

What is a carbonyl group?

A

C=O

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26
Q

What compounds are classified as carbonyl compounds?

A

Aldehydes and Ketones

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27
Q

What defines an aldehyde?

A

A hydrogen joined to a carbonyl group

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28
Q

What defines a ketone?

A

If there are only hydrocarbon groups joined to the carbonyl

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29
Q

How do carbonyl groups affect bonding?

A

They form polar bonds, because oxygen is much more electronegative than carbon

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30
Q

What are the physical properties on aldehydes?

A

The have distinctive smells - short carbon chains = unpleasant, long carbon chains = pleasant

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31
Q

What are the relative boiling points of aldehydes, ketones, alcohols and alkanes?

A

Alkanes < Aldehydes < Ketones < Alcohols

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32
Q

Why do aldehydes and ketones have lower boiling points than alcohols?

A

They have intermediate intermolecular forces, only dipole dipole, so hydrogen bonds are not able to form because all the hydrogen atoms are attached to carbon atoms only.

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33
Q

How soluble are aldehydes and ketones?

A

Smaller aldehydes and ketones are soluble because they can form hydrogen bonds with water. Solubility decreases with chain length

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34
Q

What can aldehydes and ketones be reduced to?

A

Alcohols

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35
Q

What is the reagent for reduction of aldehydes and ketones?

A

Lithium Aluminium Hydride

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36
Q

How are reductions of carbonyl compounds carried out?

A

With both the carbonyl and reducing agent in dry ether

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37
Q

What reagents can be used to oxides aldehydes to carboxylic acids?

A

Acidified potassium dichromate, Fehling’s, Benedict’s, Tollens’

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38
Q

What is the colour change for acidified potassium dichromate?

A

Orange —-> green

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39
Q

What is the colour change for Fehling’s?

A

Deep blue solution —-> red precipitate

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40
Q

What is the colour change for Benedict’s?

A

Deep blue solution —-> red precipitate

41
Q

What is the colour change for Tollens’?

A

Colourless solution —-> Silver mirror

42
Q

How can you distinguish between aldehydes and ketones?

A

Aldehydes react with Benedict’s, Fehling’s and Tollens’, ketones do not

43
Q

How do aldehydes and ketones react with iodine?

A

Carbonyls with CH3CO react with iodine to for triiodomethane - a yellow precipitate

44
Q

What is the equation for the reaction between a carbonyl compound and iodine?

A

COCH3 + 3I2 + 4OH- ——> RCOO- + CHI3 + 3I- + 3H20

45
Q

How can Brady’s reagent be used to distinguish between aldehydes and ketones?

A

An orange precipitate forms if a carbonyl is present
The precipitate can be purified by re-crystallisation
Each different carbonyl give a crystal with a different melting point
If the melting points are measured and compared to a table of known values, the compound can be identified

46
Q

Under what conditions do reactions with hydrogen cyanide occur?

A

In aqueous alkaline solution containing potassium cyanide

47
Q

What is the equation for addition of HCN to propanal?

A

CH3CH2CHO + HCN —-> CH3CH3CH(OH)CN

48
Q

What is the equation for addition of HCN to butanone?

A

CH3COCH2CH3 + HCN —-> CH3C(CN)(OH)CH2CH3

49
Q

What type of mechanism is the addition of hydrogen cyanide to a carbonyl?

A

Nucleophilic addition

50
Q

What does the addition of HCN involve?

A

The hydrogen atom attaches to the oxygen of the carbonyl and a cyanide group attaches to the carbon of the carbonyl group

51
Q

How many steps are in the nucleophillic addition of HCN?

A

Two , and an intermediate is formed

52
Q

How can optical activity be used as evidence for the mechanism of addition of HCN?

A

The arrangement of the two atoms or groups attached to the C=O is planar, so the cyanide ion can attack from above or below. Creates a chiral carbon, but with a equal amounts of dextrorotatory and laevorotatory enantiomers, no optical activity.

53
Q

What is the common name for methanoic acid?

A

Formic acid

54
Q

How is the charge distributed in a carboxylate (COO-) ion?

A

Evenly

55
Q

What are the physical properties of carboxylic acids?

A

They have distinctive smells and sour tastes

56
Q

What are the relative boiling points for carboxylic acids?

A

Very high

57
Q

Why do carboxylic acids have high boiling points?

A

They have three polar bonds in the carboxylic acid group which give them strong intermolecular forces and hydrogen bonding

58
Q

How does the length of the carbon chain in a carboxylic acid affect the boiling point?

A

The longer the chain, the higher the boiling point because London forces increase

59
Q

Why do shorter carboxylic acids form dimers?

A

In the absence of a solvent, two molecules hydrogen bond with one another

60
Q

What type of carboxylic acids are soluble in water?

A

Shorter chain ones, as they can form hydrogen bonds with water

61
Q

How does chain length affect solubility in carboxylic acids?

A

Solubility decreases with increasing chain length

62
Q

What are the two main methods of producing carboxylic acids?

A

Oxidation and hydrolysis

63
Q

What are the conditions for oxidation of a primary alcohol or aldehyde to form a carboxylic acid?

A

Acidified potassium dichromate (VI) and reflux

64
Q

What is the equation for the oxidation of propan-1-ol to propanoic acid?

A

CH3CH2CH2OH + 2[O] —-> CH3CH2COOH + H20

65
Q

What is the equation for the oxidation of propanone to propanoic acid?

A

CH3CH2CHO + [O] —-> CH3CH2COOH

66
Q

What can be hydrolysed to from a carboxylic acid?

A

Nitriles and organic compounds containing CN group

67
Q

What are the conditions for hydrolysing nitriles to form carboxylic acids?

A

Reflux with either a dilute acid or aqueous alkali

68
Q

What is the equation for the hydrolysis of propanenitrile with dilute acid?

A

CH3CH2CN + H+ + 2H2O —-> CH3CH2COOH + NH4+

69
Q

What is the equation for the hydrolysis of butanenitrile with aqueous alkali?

A

CH3CH2CH2CN + OH- + H2O —-> CH3CH2CH2COO- + NH3
Butanoate ion then converted into acid by adding dilute acid:
CH3CH2CH2COO- + H+ —-> CH3CH2CH2COOH

70
Q

What are the four main reactions of carboxylic acids?

A

Reduction
Neutralisation
Halogenation
Esterification

71
Q

What is the product of neutralisation of a carboxylic acid?

A

A carboxylate salt

72
Q

Which reducing agent is used to reduce carboxylic acids?

A

Lithium aluminium hydride

73
Q

What is the equation for the neutralisation of ethanoic acid using sodium hydroxide?

A

CH3COOH + NaOH —-> CH3COONa + H2O

74
Q

What is the product of halogenation of a carboxylic acid?

A

Acyl chloride

75
Q

What are the conditions for halogenation of carboxylic acids?

A

Phosphorus (V) chloride and anhydrous conditions

76
Q

Why are anhydrous conditions used for halogenation of carboxylic acids?

A

Because both the reagent and the acyl chloride react vigorously with water

77
Q

What is the equation for the halogenation of propanoic acid?

A

CH3CH2COOH + PCl5 —-> CH3CH2COCl + POCl3 + HCl

78
Q

What are the conditions for esterification of carboxylic acids?

A

Alcohol and a small amount of acid catalyst, often conc H2SO4

79
Q

What is the equation for the esterification of mathanoic acid with ethanol?

A

HCOOH + CH3CH2OH HCOOCH2CH3 + H2O

80
Q

What is the general formula for acyl chlorides?

A

RCOCl

81
Q

What are acyl chlorides prone to?

A

Nucleophillic attack, as the carbon is joined to two electronegative atoms, so is electron deficient

82
Q

How do acyl chlorides react with cold water?

A

Vigorously, forming a carboxylic acid and releasing hydrogen chloride gas, appearing as misty fumes

83
Q

What is the equation for the reaction of ethanoyl chloride and water?

A

CH3COCl + H2O —-> CH3COOH + HCl

84
Q

How do acyl chlorides react with alcohols?

A

They readily react with ethanol to form ab ester and hydrogen chloride gas

85
Q

What is the equation for the reaction of ethanoyl chloride with ethanol?

A

CH3COCl + CH3CH2OH —-> CH3COOCH2CH3 + HCl

86
Q

How do acyl chlorides react with concentrated ammonia solution?

A

In two steps, an NH2 group joins with the carbonyl group to produce an amide as well as ammonium chloride

87
Q

What is the equation for the reaction between ethanoyl chloride and conc ammonia?

A

CH3COCl + 2NH3 —-> CH3CONH2 + NH4Cl

88
Q

How do acyl chlorides react with primary amines?

A

One H form the amine react with Cl to form HCl and the rest of the compound is attached to the carbonyl group

89
Q

What is the equation for the reaction between ethanoyl chloride and methylamine?

A

CH3COCl + CH3NH2 —-> CH3CONHCH3 + HCl

90
Q

Why don’y acyl chlorides react with tertiary amines?

A

There is no H to react with the Cl to form HCl

91
Q

What are the physical properties of esters?

A

Colourless liquids with low melting and boiling points, insoluble in water, no hydrogen bonding. Generally pleasant smell.

92
Q

What are the two types of hydrolysis of esters?

A

Hydrolysis in acidic solution and in alkaline solution

93
Q

What is the equation for hydrolysis of ethyl ethanoate with a sulfuric acid catalyst?

A

CH3COOCH2CH3 + H2O CH3COOH + CH3CH2OH

94
Q

What is the equation for the hydrolysis of methyl propanoate in alkaline solution?

A

CH3CH3COOCH3 +NaOH —> CH3CH2COO- + Na+ + CH3OH

95
Q

What is saponification?

A

Alkaline hydrolysis of esters to form an alcohol and a stearate, commonly used in soaps

96
Q

What is condensation polymerisation?

A

Each time two monomer molecules join together, another small molecule is formed
Usually two different monomers react together

97
Q

What is the small molecule formed during condensation polymerisation?

A

Often water

98
Q

How are polyesters formed?

A

Through condensation polymerisation

99
Q

What are the monomers of polyesters?

A

A diol and a dicarboxylic acid

edexcel a level chemistry (20 decks)

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