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Chemistry (Tara) > Organic chem - 4 > Flashcards

Organic chem - 4 Flashcards

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1
Q

What does planar carbon refer to?

A

A carbon that does not have four single bonds./ Any carbon that is not tetrahedral.

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2
Q

Aldehydes are a ………… series, containing the - CHO functional group

A
  • Homologous

- CHO

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3
Q

What is aldehydes general formula?

A

RCHO

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4
Q

What is ‘R’ in RCHO?

A

Either a hydrogen atom or an alkali group.

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5
Q

What group do aldehydes contain in their structure?

A

A carbonyl group.

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6
Q

What is a carbonyl group?

A

C = O

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7
Q

Is the carbonyl group in aldehydes polar or non-polar?

A

Polar

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8
Q

Why is the carbonyl group in aldehydes polar?

A

Due to the difference in electronegativity value of the carbon and oxygen atoms.

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9
Q

Is the oxygen delta + or delta - ? (In general formula)

A

Delta -

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10
Q

Is the carbon delta + or delta - ? (In general formula)

A

Delta +

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11
Q

Why is the oxygen delta - ? (In general formula)

A

Because it is more electronegative.

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12
Q

Why is the carbon delta + ? (In general formula)

A

As it is less electronegative.

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13
Q

What forces of attractions are between the aldehyde molecules?

A

Dipole-dipole attractions.

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14
Q

Why is there dipole-dipole attractions between aldehydes?

A

Due to the carbonyl group.

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15
Q

What has higher boiling points, alkanes or aldehydes?

A

Aldehydes

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16
Q

What has higher boiling points, alcohols or aldehydes?

A

Alcohols

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17
Q

Are the lower aldehydes soluble or insoluble in water?

A

Soluble

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18
Q

Are the lower aldehydes soluble or insoluble in non-polar solvents such as cyclohexane?

A

Soluble

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19
Q

Name a non-polar solvent that the lower aldehydes are soluble in.

A

Cyclohexane

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20
Q

Why are the lower aldehydes soluble in water, a polar solvent?

A

Due to the hydrogen bonding that occurs between the oxygen of the carbonyl group of the aldehyde and the hydrogen of water.

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21
Q

Are the higher aldehydes soluble or insoluble in water?

A

Insoluble

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22
Q

Why are the higher aldehydes insoluble in water?

A

As the non-polar chain of the aldehyde molecule has greater influence.

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23
Q

What will aldehydes end in when naming?

A
  • anal
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24
Q

Name 3 examples of aldehydes and draw them.

A
  • Methanal
  • Ehanal
  • Propanal
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25
Q

Methanol at r.t

A
  • Gas
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26
Q

Ethanal at r.t

A
  • Volatile gas
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27
Q

Where is the functional group always written?

A

To the right of the molecule

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28
Q

What is the carbon of the functional group always when naming?

A

C1

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29
Q

What does solubility depend on?

A

The length of the carbon chain.

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30
Q

What is another name for methanal?

A

Formaldehyde

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31
Q

Draw methanal and give its molecular formula.

A
  • HCHO
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32
Q

Draw ethanal and give it’s molecular formula.

A
  • CH₃CHO
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33
Q

Draw propanal and give it’s molecular formula.

A
  • C2H5CHO
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34
Q

Draw butanal and give it’s molecular formula.

A
  • C₃H7CHO
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35
Q

How many structural isomers does C4H8O have?

A

3

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36
Q

Name the three isomers of C4H8O

A
  • Butanal
  • 2 methylpropanal
  • Butanone
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37
Q

What are aldehydes isomers of?

A

Ketones

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38
Q

What are aldehydes and ketones?

A

Aldehydes of each other

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39
Q

What is benzaldehyde?

A

An aromatic aldehyde.

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40
Q

What is another name for benzaldehyde?

A

Phenylmethanal

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41
Q

Where is phenylmethanal (benzaldehyde) found?

A

In almond oil of almond kernels found.

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42
Q

What is ketones general formula?

A

R1COR2

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43
Q

What is R1 and R2 in R1COR2?

A

Alkali groups which may be the same or different.

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44
Q

What can’t R1 and R2 be?

A

Hydrogen

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45
Q

What do ketones contain in their functional group other than alkali groups?

A

A carbonyl group

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46
Q

What is the carbonyl group in ketones?

A
  • C = O
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47
Q

What do the physical properties of ketones show a lot of similarities to?

A

Aldehydes.

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48
Q

What has a higher boiling point aldehydes or ketones?

A

Ketones

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49
Q

Why do ketones have higher boiling points than aldehydes?

A

Due to the dipole-dipole attractions between the polar carbonyl groups.

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50
Q

What has higher boiling points, ketones or alcohols?

A

Alcohols.

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51
Q

Are the lower ketones soluble or insoluble in polar water?

A

Soluble

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52
Q

Why are the lower ketones soluble in water?

A

Due to the hydrogen bonding between the oxygen of the carbonyl group of the ketone and the hydrogen in water.

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53
Q

When does the solubility in water decrease?

A

As the length of the non-polar carbon chain increases.

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54
Q

Are ketones soluble or insoluble in non-polar solvents such as cyclohexane?

A

Soluble

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55
Q

Name a non-polar solvent that ketones are soluble in.

A

Cyclohexane

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56
Q

Is propanone a polar or non-polar solvent?

A

Polar

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57
Q

Where is propanone found?

A

In nail varnish remover

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58
Q

What is another name for acetone?

A

Propanone

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59
Q

What does naming ketones end in?

A
  • Anone
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60
Q

Name two examples of ketones.

A
  • Propanone

- Butanone

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61
Q

What is the carbon of the functional group never? (ketones)

A

The first or last carbon of the molecule.

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62
Q

What is the position of the carbon of the functional group of ketones indicated by?

A

By the smallest possible number.

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63
Q

What is the first member of the homologous series? (ketones)

A

Propanone.

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64
Q

Why is propanone the first member of the homologous series (ketones) ?

A

As ketones can only have a minimum of 3 carbons in the chain.

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65
Q

What is propanone?

A

A solvent in nail polish remover.

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66
Q

Draw the structure formula of propanone and give it’s molecular formula.

A
  • CH3COCH3
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67
Q

Draw the structure formula of butanone and give it’s molecular formula.

A
  • CH₃COC₂H5
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68
Q

What is the carboxylic acid’s general formula?

A

RCOOH

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69
Q

What is R in the carboxylic acid’s general formula?

A

Either hydrogen or an alkali group.

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70
Q

What is the functional group of carboxylic acid?

A
  • COOH
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71
Q

What has higher boiling points, carboxylic acids or the corresponding alcohols?

A

Carboxylic acids

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72
Q

Why do carboxylic acids have higher boiling points than the corresponding alcohols?

A

Due to the hydrogen bonding present between molecules caused by the polar -OH group present in the functional group.

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73
Q

What is the hydrogen bonding between molecules in carboxylic acids caused by?

A

The polar -OH group present in the functional group.

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74
Q

What do the molecules of carboxylic acids group together in?

A

Twos

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75
Q

What are the twos that carboxylic acids group together in called?

A

Dimers

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76
Q

What are the dimers held together by?

A

Hydrogen bonds.

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77
Q

What has the highest boiling points of all the homologous series?

A

Carboxylic acids

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78
Q

What do the dimers that are held together by carboxylic acids cause?

A

More energy is need to break them down.

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79
Q

What are carboxylic acids at r.t?

A

Liquids

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80
Q

Why are carboxylic acids liquids at r.t?

A

Due to the hydrogen bonds holding the molecules together.

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81
Q

Are the lower carboxylic acids soluble or insoluble in water?

A

Soluble

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82
Q

Why are the lower carboxylic acids soluble in water?

A

Due to the formation of hydrogen bonds with water

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83
Q

What does the oxygen of the carbonyl group in carboxylic acids form with in water?

A

The oxygen of the carbonyl group of the acid forms a hydrogen bond with the hydrogen in water.

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84
Q

What does the hydrogen of the -OH group of the acid form?

A

Forms another hydrogen bond with the oxygen of water.

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85
Q

What happens as the length of the carbon chain increases?

A

Solubility decreases

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86
Q

Are the higher members of carboxylic acids soluble or insoluble in non-polar solvents?

A

Soluble

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87
Q

Name a non-polar solvent that the higher members of carboxylic acids are soluble in.

A

Cyclohexane

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88
Q

When naming the carboxylic acids. where is the functional group?

A

Always on the right hand side of the molecule

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89
Q

The right hand side of a carboxylic acids molecule is always….

A

C1

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90
Q

What are the endings of carboxylic acids?

A
  • anoic acid
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91
Q

Name 3 examples of carboxylic acids.

A
  • Methanoic acid
  • Ethanoic acid
  • Propanoic acid
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92
Q

Give another name for methanoic acid

A

Formic acid

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93
Q

Where is methanoic acid found?

A

In nettle and stinging ants

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94
Q

What manufacturing is ethanoic acid involved in?

A
  • Manufacture of cellulose acetate, which is used in varnishes
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95
Q

Where is ethanoic acid found?

A

In vinegar

96
Q

Name an aromatic carboxylic acid.

A

Benzoic acid

97
Q

What is propanoic acid and benzoic acid used as?

A

Food preservatives

98
Q

Name an unusual carboxylic acid and why it’s unusual.

A
  • Methanoic acid

- As it can act like an aldehyde

99
Q

Why can methanoic acid act like an aldehyde?

A

As its structure contains the aldehyde functional group.

100
Q

Give the molecular formula and draw methanoic acid/formic acid.

A

HCOOH

101
Q

Give the molecular formula and draw ethanoic acid / acetic acid.

A

CH₃COOH

102
Q

Give the molecular formula and draw propanoic acid.

A

C₂H5COOH

103
Q

Give the molecular formula and draw butanoic acid.

A

C₃H7COOH

104
Q

Name 2 carboxylic acid that are used as food preservatives.

A
  • Benzoic acid

- Propanoic acid

105
Q

What is the general formula of esters?

A

R1COOR2

106
Q

What is R1 in the general formula of esters?

A

Either a hydrogen or and alkyl group.

107
Q

What is R2 in the general formula of esters?

A

An alkyl group

108
Q

How are esters formed?

A

Formed by the reverse reaction between a carboxylic acid and an alcohol.

109
Q

What is the formation of esters caused by the reverse reaction between a carboxylic acid and an alcohol called?

A

A condensation reaction

110
Q

When does a condensation reaction occur?

A

When two different molecules combine to form a more complex molecule with the production of a smaller molecule such as H2O.

111
Q

Do esters have relatively high or low boiling points?

A

Relatively low boiling points

112
Q

What forces of attraction is present between ester molecules?

A

Dipole-dipole

113
Q

Why do esters have relatively low boiling points?

A

Due to the dipole-dipole attractions between molecules.

114
Q

Are the lower esters soluble or insoluble in polar water?

A

Soluble

115
Q

Why are the lower esters soluble in polar water?

A

As the oxygen of the carbonyl group forms hydrogen bonds with the hydrogen of water.

116
Q

What happens to the solubility of esters as the carbon chain length increases?

A

It decreases

117
Q

Are the higher esters soluble or insoluble in non-polar solvents?

A

Soluble

118
Q

Name a non-polar solvent that the higher esters are soluble in.

A

Cyclohexane

119
Q

Name two homologous series that are isomers of each other.

A

Carboxylic acid and esters

120
Q

What are the names of the 2 isomers of C3H6O2

A

Propanoic acid and methylethanoid

121
Q

What can’t be forgotten when writing out a condensation reaction equation?

A

Don’t forget the H2O

122
Q

What is the first step in condensation reactions?

A

Take the H out of the functional group

123
Q

Where does R1 of the ester of the carbon of the functional group come from?

A

The carboxylic acid

124
Q

Where does the R2 of the ester come from?

A

The alcohol

125
Q

How are esters named?

A

‘Backwards@

126
Q

What end comes first when naming esters?

A

The alkyl group of the end of the molecule

127
Q

What ending is given to the alkyl group of the end of the molecule in esters?

A

-yl

128
Q

What ending is given to the front part of the molecules in esters?

A

-anoate

129
Q

Which parts of ethyl butanoate were originally homologous series?

A

ethyl - alcoholl

butanoate - carboxylic acid

130
Q

Name the molecule CH3COOC2H5

A
  • End is ethyl
  • Front is ethanoate
    = Ethyl ethanoate
131
Q

Name the molecule HCOOC3H7

A
  • End is propyl

- Front is methanoate = propyl methanoate

132
Q

Name the molecule HCOOCH3

A

Methyl formate

133
Q

Name the molecule C2H5COOC2H5

A

Ethyl acetate

134
Q

Write the formula for butyl ethanoate

A

C₆H12O₂

135
Q

Write the formula for propyl methanoate

A

C₄H₈O₂

136
Q

Write the formula for ethyl propanoate

A

C5H10O₂

137
Q

Write the formula for ethyl ethanoate

A

C₄H₈O₂

138
Q

What does ‘poly’esters mean?

A

Many

139
Q

What name is given to synthetic fabrics such as ‘terylene’?

A

Polyesters

140
Q

What are polyesters used for?

A

Used in the clothing industry and other fabric industries i.e carpet, sails etc.

141
Q

What are polyesters?

A

Polymers what consist of hundreds of thousands of ester molecules liked together under certain conditions of temperature and pressure.

142
Q

Are polyesters found naturally or artificial?

A

Artificial

143
Q

Name 2 esters that occur naturally

A

Fats and oils

144
Q

Give an example of an ester that occurs naturally which is used to make soap.

A

Glyceryl tristearate

145
Q

What role is glyceryl tristearate in the preparation of soap?

A

The limiting reactant

146
Q

Basic meaning of limiting reactant

A

The one that runs out first

147
Q

Find the molecular mass of glyceryl tristearate

A

890

148
Q

Learn the structure of glyceryl tristearate!!

A

DONE

149
Q

What is noticable upon dealing with esters?

A

They have distinct aromas (smells)

150
Q

Name 2 smells that esters are responsible for?

A
  • petals of flowers

- fruits

151
Q

4 examples of the use of synthetic esters

A
  • perfumes
  • soaps
  • bath salts
  • deodorants
152
Q

Why are synthetic esters manufactoured?

A

To imitate smells for use in perfumes etc.

153
Q

What is ethyl ethanoate used as?

A

A non-polar solvent

154
Q

Why are the preparation of aldehydes, ketones and a carboxylic acids, redox reactions?

A

As the alcohol is oxidised and the oxiding agent(sodium dichromate) is reduced during the preparation..

155
Q

What is the oxidising agent in the preparation of aldehydes, ketones and carboxylics acids?

A

Sodium dichromate

156
Q

What does the reduction of the dichromate ion during redox reactions lead to?

A

A colour change of orange to green as Cr(+6) is reduced to Cr(+₃)

157
Q

What is reduced during redox reactions?

A

Dichromate ion

158
Q

Name all 3 reactions of ethanal

A
  • With acidified potassium permanganate
  • With Fehling’s solution
  • With Tollen’s Reagent
159
Q

What are the steps in the reaction of ethanal with acidified potassium permanganate?

A
  • Place a few cm3 of ethanal into a test tube with some acidified permanganate (VII)
  • Heat gently in a water bath for a few minutes
160
Q

What colour is Fehling’s solution?

A

Blue

161
Q

What colour is potassium manganate (VII)?

A

Purple

162
Q

What is the result of the reaction of ethanal with acidified potassium permanganate?

A

Manganate (VII) purple → colourless

163
Q

What does the manganate (VII) go from purple to colourless in the reaction of ethanal with acidified potassium permanganate?

A

As the ethanal is a reducing agent and reduces Mn(+7) to Mn(+₂).

164
Q

What is the equation for the reaction of ethanal with acidified potassium permanganate?

A

CH3CHO+Mn(+7) → CH3COOH +Mn(+₂)

165
Q

What are the steps in the reaction of ethanal with Fehling’s solution

A
  • Place a few cm3 of ethanal into a test tube.
  • Add equal volumes of Fehlings solution A+B
  • Heat gently and shake to mix
166
Q

What colour occurs when equal volumes of Fehlings solution are added in the reaction of ethanal with Fehling’s solution and why?

A

Blue due to the presence of Cu(II).

167
Q

What is the result in the reaction of ethanal with Fehling’s solution?

A

Fehlings solution blue → red precipitate

168
Q

Why does the colour change to red in the reaction of ethanal with Fehling’s solution?

A

Due to the ethanal acting as a reducing agent with reduces Cu₂+(blue) → Cu+ (red)

169
Q

What is the equation for the reaction of ethanal with Fehling’s solution?

A

CH₃CHO + CU(₂+) → CH₃COOH + Cu+

170
Q

What colour is CH3CHO?

A

Colourless

171
Q

Name for CH3CHO

A

Acetaldehyde

172
Q

What gets oxidised in the reaction of ethanal with Fehling’s solution?

A

Ethanal

173
Q

What does ethanal get oxidised to in the reaction of ethanal with Fehling’s solution?

A

Ethanoic acid

174
Q

What are the steps in the reaction of ethanal with Tollen’s Reagent?

A
  • Place a few cm3 of silver nitrate solution into a test tube. Add a small amount of NaOH
  • Add a few drops of ammonia until the silver oxide pt disappears.
  • Add a few drops of ethanal and warm gently
175
Q

What is the result in the reaction of ethanal with Fehling’s solution?

A

A deposit of metallic silver is seen on the inside of the test tube.

176
Q

Why is a deposit of metallic silver seen on the inside of the test tube in the reaction of ethanal with Fehling’s solution?

A

Due to the silver in Tollens Reagent which has an oxidisation number of Ag(+1) being reduced by ethanal to metallic silver which has an oxidation number of Ag(0).

177
Q

What is the equation in the reaction of ethanal with Fehling’s solution?

A

CH₃CHO + Ag(+) → CH₃COOH + Ag(↓)

178
Q

What is used to produce an aldehyde?

A

A primary alcohol

179
Q

What would happen if we were to oxidise a secondary alcohol such as propan-2-ol in a similar manner to producing an aldehyde?

A

We would produce a corresponding ketone, propanone.

180
Q

Are ketones easily oxidised to become the carboxylic acid?

A

No

181
Q

Is it necessary to use the same precautions i.e an excess of alcohol over oxidising agent with ketones and explain why?

A

No as ketones are not easily oxidised

182
Q

What happens in the reduction of aldehydes?

A

Aldehydes are reduced to the primary alcohol using hydrogen and a nickel catalyst.

183
Q

What is the equation for the reduction of aldehydes?

A

CH₃CHO + H₂ → C₂H5OH

184
Q

What happens in the reduction of ketones?

A

Ketones are reduced to the secondary alcohol using hydrogen and a nickel catalyst.

185
Q

Nickel (catalyst) ‘symbol’

A

Ni

186
Q

Equation for the reduction of ketones.

A

CH₃COCH₃ + H₂ → CH₃CH(OH)CH₃

187
Q

Short description of sodium carbonate.

A

White powder

188
Q

What are the steps in the reaction of ethanoic acid with sodim carbonate?

A
  • A spatula load of sodium carbonate was placed into a test tube.
  • A few cm3 of ethanoic acid was added
189
Q

What was the result in the reaction of ethanoic acid with sodim carbonate?

A

Effervescence was observed as carbon dioxide was given off. This carbon dioxide quenched a lighted taper held at the mouth of the test tube.

190
Q

Equation for the reaction of ethanoic acid with sodium carbonate.

A

2CH₃COOH + Na₂CO₃ → 2CH₃COONa + CO₂ +H₂0

191
Q

Briefly describe magneisiam metal

A

Silver, burns with a bright light

192
Q

Steps in the reaction of ethanoic acid with magneisiam metal.

A
  • A test tube was quarter filled with ethanoic acid.

- About 3cm of masgneisiam ribbon was added.

193
Q

Result of the reaction of ethanoic acid with magneisiam metal.

A

The magneisiam ribbon disappeared and hydrogen gas was given off.

194
Q

Equation for the reaction of ethanoic acid with magneisiam metal.

A

2CH₃COOH +Mg → (CH₃COO)₂Mg +H₂

195
Q

Magneisiam ethanoate molecular formula

A

(CH₃COO)2Mg

196
Q

Which reaction is referred to as an esterification reaction?

A

The reaction of ethanoic acid with ethanol

197
Q

What can the reaction of ethanoic acid with ethanol be called other then an esterification reaction?

A

A substitution reaction

198
Q

Why can the reaction of ethanoic acid with ethanol also be called a substitution reaction?

A

As the hydrogen of the -OH group of acid is replaced by an alkyl group from an alcohol.

199
Q

What can the reaction of ethanoic acid with ethanol be called other than an esterification reaction and a substitution reaction?

A

A condensation reaction.

200
Q

Why can the reaction of ethanoic acid with ethanol be called a condensation reaction?

A

As two different molecules react to produce a more complex molecule with the production of a smaller molecule such as water.

201
Q

What happens when ethanoic acid and ethanol are refluxed together?

A

The ester ethyl ethanoate is formed.

202
Q

What happens in the reaction of ethanoic acid with ethanol?

A

A carboxylic acid and an alcohol are reacted together under reflux in the presence of concentrated sulfuric acid.

203
Q

What is the purpose of the concentrated sulfuric acid in the equation : CH₃COOH + C₂H₅OH ⇋ CH₃COOC₂H₅ + H₂O

A
  • Acts as a dehydrating agent and a catalyst
204
Q

What does the dehydrating agent (concentrated sulfuric acid) in the equation : CH₃COOH + C₂H₅OH ⇋ CH₃COOC₂H₅ + H₂O cause?

A

Causes the water concentration to decrease which drives the position of equilibrium to the right, favouring the forward reaction so more ester, ethyl ethanoate is produced.

205
Q

What are carboxylic acids reduced to first in the reduction of carboxylic acids?

A

An aldehyde

206
Q

What are carboxylic acids reduced to after firstly being reduced to an aldehyde?

A

A primary alcohol

207
Q

What is used to reduce carboxylic acids to firstly an aldehyde then a primary alcohol? (reduction of carboxylic acids)

A

Using hydrogen and a nickel catalyst.

208
Q

What is the equation for the reduction of carboxylic acids?

A

CH₃COOH + H₂ → CH₃CHO + H₂ → C₂H₅OH

209
Q

CH₃COOH + H₂ → CH₃CHO + H₂ → C₂H₅OH Name the condition and the reagent.

A 
Condition = Nickel catalyst
Reagent = H₂
210
Q

Draw the funtional group of aldehydes. (L.C)

A

In notes

211
Q

Draw the functional group of carboxylic acids. (L.C)

A

In notes

212
Q

What is an ester? (L.C)

A

A compound formed when the hydrogen of the functional group of a carboxylic acid is replaced by an alkyl radical of an alcohol.

213
Q

Give the two functions of using concentrated sulfuric acid in an esterification reaction. (L.C)

A
  • As a catalyst

- As a dehydrating agent

214
Q

Name the following molecule, CH₃CHBrCHO. (L.C)

A

n

215
Q

Which of the following has a higher boiling point, CH₃CHO or CH₃COOH. Explain your reasoning. (L.C)

A

n

216
Q

How many tetrahedral carbons would you find in ethyl methanoate? (L.C)

A

n

217
Q

What is meant by a condensation reaction? (L.C)

A

Occurs when two different moleculescombine to form a more complex molecule with the production of a smaller molecule such as H₂0.

218
Q

Draw and name the final product produced by the reduction of butanone. Identify the reagent used in this reaction. (L.C)

A

n

219
Q

Classify the following alcohols - propan-2-ol, butan-1-ol. (L.C)

A

n

220
Q

A sample of ethanoic acid (CH₃COOH) was prepared by the oxidation of ethanol. Describe and explain the colour change observed in the reaction flask as the ethanol was oxidised. (L.C)

A
  • Orange to green

- dicromate reduced to chromium

221
Q

Reflux is a widely used technique in organic chemistry. Identify an experiment from your course where you refluxed a mixture. Draw a fully labeled diagram of the reflux apparatus used in this experiment. (L.C)

A 
- Preparation of soap
Draw : Flask with contents shown or labeled
- Anti-bumping granules
- condenser in correct position
- Labelled source of heat.
222
Q

Reflux is a widely used technique in organic chemistry. Identify an experiment from your course where you refluxed a mixture. What happened to the liquid in the flask during reflux? (L.C)

A
  • Liquid evaporated / hot vapour rose
223
Q

Reflux is a widely used technique in organic chemistry. Identify an experiment from your course where you refluxed a mixture. How did refluxing this mixture help bring the reaction to completion? (L.C)

A

Allowed enough time to bring reaction to completion.

224
Q

A sample of ethanoic acid (CH₃COOH) was prepared by the oxidation of ethanol. Describe your observations when a small quantity of solid sodium carbonate was added to a sample of the ethanoic acid produced. Write a balanced chemical equation for the reaction which occured. (L.C)

A
  • Effervescence / gas given off

- Na₂CO₃ + 2CH₃COOH → 2CH₃COONa + H₂0 + CO₂

225
Q

Alcohol X ⇋ Aldehyde Y ⇋ Carboxylic acid Z

Name X,Y and Z (L.C)

A 
X = Ethanol
Y = Ethanal
Z = Ethanoic acid
226
Q

Give a major use for ethanoic acid. (L.C)

A

As a flavouring agent

227
Q

Draw the structure of ethanal, showing the boding between the atoms. (L.C)

A

In notes

228
Q

What ester is formed from ethanol and ethanal? (L.C)

A

Ethylethanoate

229
Q

Give two reasons why alcohols have a higher boiling point than corresponding alkanes. (L.C)

A
  • Alcohols have higher relative molecular mass

- Intermolecular hydrogen bonds

230
Q

Explain why the difference in boiling points between methane and methanol is 226.5K while the difference in boiling points between butane and butanol is only 119K. (L.C)

A

Due to a longer carbon chain / hydrogen bonding is weaker in butanol.

231
Q

Describe in general terms, the solubilities of methane and methanol, butane and butanol in water. (L.C)

A

Methane - virtually insoluble
Methanol - compleatly soluble
Butane - virtually insoluble
Butanol - slightly soluble

232
Q

A group of students prepared ethanal by slowly adding an aqueous solution of ethanol and sodium dichromate to a hot aquous solution of sulfuric acid. Why was the receiving vessel cooled in ice-water? (L.C)

A
  • Volatile product / ethanal has low b.p
233
Q

A group of students prepared ethanal by slowly adding an aqueous solution of ethanol and sodium dichromate to a hot aquous solution of sulfuric acid. State 2 features of the preparation that are necessary to maximise the yield of ethanal and for each feature, explain. (L.C)

A
  1. Excess ethanol - so it doesn’t go to ethanoic acid

2. Dichromate in funnel - small amount of oxidising agent in flask

234
Q

A group of students prepared ethanal by slowly adding an aqueous solution of ethanol and sodium dichromate to a hot aquous solution of sulfuric acid. Describe and account for the colour change which is observed during the addition of ethanol and sodium dichromate solution to the hot acid. (L.C)

A

Describe - Orange solution added to colourless solution turns green
Account - Cr(VI) is reduced to Cr(III)

235
Q

A group of students prepared ethanal by slowly adding an aqueous solution of ethanol and sodium dichromate to a hot aquous solution of sulfuric acid. Describe how you would carry out Fehling’s test on a sample of ethanal. What observation would you expect to make in this test? (L.C)

A

Test - Mix equal amounts of Fehling’s 1 and Fehling’s 2 and add ethanal and warm
Observe - Brick-red → precipitate produced

Chemistry (Tara) (50 decks)

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