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OCR A Chemistry > 6.1 - Aromatic Compounds and Carbonyls > Flashcards

6.1 - Aromatic Compounds and Carbonyls Flashcards

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1
Q
A
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2
Q

What did Kekule’ say about Benzene?

A
  • Ring of carbon atoms with alternating single and double bonds between them - Each carbon is bonded to 2 other carbon atoms and a hydrogen giving a formula of C6H6. - Benzene has a planar shape/cyclic shape
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3
Q

What does the delocalised model of benzene say?

A
  • Each of the 6 carbon bonds donate one electron from it’s p-orbital. These electrons combine to form a ring of delocalised electrons ABOVE and BELOW the plane of the molecules. This overlapping of p-orbitals forms a pi-system. - All the bonds are the same length - Electrons are said to be delocalised because they do not belong to a specific carbon atom.
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4
Q

Give 3 reasons why Kekule’ model was disapproved

A
  • Bond lengths - Resistance to reaction - Enthalpy change of hydrogenation
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5
Q

Using the concept of bond lengths, explain why Kekule’ model was disapproved

A

One reason why Kekule’ model was disapproved is due to the bond lengths. Under Kekule’ structure of benzene, there are 3 C=C bonds (length of 135pm each) and 3 single bonds (length of 147pm each). However, X-ray diffraction techniques have show that ALL 6 carbon bonds in benzene are the same length at 140pm (between 135 and 147pm)., disapproving Kekule’ model.

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6
Q

Using the concept of resistance to reaction, explain why Kekule’ model was disapproved

A

Under Kekule’ model of benzene, you would expect Benzene to go through similar reactions to alkenes (because of the double bond). For example, alkenes such as propene undergo electrophilic addition. However, benzene tends to undergo electrophilic substitution reactions such as halogenation and nitration rather than electrophilic addition.

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7
Q

Using the concept of enthalpy change of hydrogenation, explain why Kekule’ model was disapproved

A

-Cyclohexene has one double bond and its enthalpy change of hydrogenation is -120kJ/mol. Therefore, as Kekule’ benzene model has 3 double bonds, we can assume that it has an enthalpy change of hydrogenation of -360kJ/mol. However, experiments have proved that Benzene’s enthalpy change of hydrogenation is actually -208kJ/mol, meaning that benzene is LESS EXOTHERMIC than Kekule’ had originally expected and so it is more ENERGETICALLY STABLE.

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8
Q

What is meant by electrophilic substitution?

A

The substitution of an atom/group with another atom/group using an electrophile.

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9
Q

What model came and replaced Kekule’ model?

A

The delocalised model of benzene.

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10
Q

What is meant by an electrophile?

A

An electron pair acceptor.

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11
Q

Give all the details for the nitration of benzene.

A

Reaction Name: Nitration of Benzene Reagents: Conc nitric acid and conc sulfuric acid (the CATALYST) Conditions : Reflux at 50 degrees celsius Electrophile used : NO2^+ Generation of electrophile: HNO3 + H2SO4 ⇄ NO2^+ + HSO4^- + H20. Regeneration of catalyst : H^+ + HSO4^- → H2S04. Equation: C6H6 + HNO3 + (H2SO4) → C6H5NO2 + H2O Product name: Nitrobenzene

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12
Q

Give all the details for the bromination of benzene

A

Reaction Name : Bromination Reagents : Bromine and a halogen carrier e.g. AlBr3 Conditions : Halogen carrier (catalyst) present. Electrophile: Br^+ Generation of electrophile : Br2 + AlBr3 ⇄ AlBr4^- + Br^+ Regeneration of catalyst: H^+ +AlBr4^- → HBr + AlBr3 Product name : Bromobenzene

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13
Q

Give the generic details for the halogenation of benzene

A

Reaction Name : Halogenation Reagents : Halogen and a halogen carrier e.g. AlX3 Conditions : Halogen carrier (catalyst) present and Reflux Electrophile: X^+ Generation of electrophile : X2 + AlX3 ⇄ AlX4^- + X^+ Regeneration of catalyst: H^+ +AlX4^- → HX + AlX3 Product name : _______benzene Where X is a halogen

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14
Q

What should you always include when answering questions about electrophilic substitution?

A

What reacts? Reagents? Equation? Electrophile and its generation? Catalyst and its regeneration? Conditions? Mechanism shown? Charges? Curly arrows? Final H^+ 5/6’s covered on intermediate?

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15
Q

Why do we need a halogen carrier in order for a halogen to react with benzene?

A

Benzene’s low electron density means that it cannot induce a dipole in the electrophile. Also, benzene’s fully delocalised ring is STABLE meaning that it will resist attack. Therefore, a halogen carrier is needed to POLARISE the electrophile, making it strong enough to react with benzene.

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16
Q

Give examples of halogen carriers

A

Iron halides - FeX3 Aluminium halides - Alx3 iron (Fe) Where X is a halogen

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17
Q

When halogen carriers are regenerated what is added to them, and what is produced?

A

Added = H^+ Produced = Halogen carrier + Hydrogen halide.

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18
Q

When electrophilic substitution occurs, what is actually happening between bonds?

A
  • The electrophile attacks benzene causing a pair of electrons to leave the delocalised system to form a bond with the electrophile. - This disrupts the delocalised system and forms an intermediate. - To restore the delocalised ring, the pair of electrons in the C=H bond moves back into the ring. Overall, there is substitution of hydrogen and the electrophile. This reaction is known as electrophilic substitution.
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19
Q

What is a Friedel-Crafts reaction?

A

A reaction that forms C-C bonds.

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20
Q

How do you carry out Friedel-Crafts reactions?

A

Reflux benzene with a halogen carrier and then reacting it with either a haloalkane (alkylation) or an acyl chloride (acylation). with ANHYDROUS conditions

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21
Q

What is meant by Friedel-Crafts alkylation?

A

A reaction where any alkyl group is put onto a benzene ring using a haloalkane and a halogen carrier under anhydrous conditions. The resultant product is an alkylbenzene.

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22
Q

Give the general equation for Friedel- Crafts alkylation

A

C6H6 + R-X → C6H5R + HX (Benzene) + (Haloalkane) → Alkylbenzene + Hydrogen halide Conditions: Reflux and a halogen carrier.

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23
Q

Give all the details of a Friedel-Crafts alkylation reaction

A

Reagents : A haloalkane and an anhydrous halogen carrier (catalyst) Conditions: Reflux in the presence of an anhydrous halogen carrier. (CATALYST) Products: Alkylbenzene + Hydrogen halide. Generation of electrophile :RX + FeX3 → R^+ + FeX4^- Regeneration of catalyst : H^+ + FeX4^- → FeX3 + HX

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24
Q

Give the general equation for the generation of the electrophile in a alkylation reaction

A

RX + FeX3 → R^+ + FeX4^-

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25
Q

Give the general equation for the regeneration of the catalyst for alkylation

A

H^+ + FeX4^- → FeX3 + HX

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26
Q

What is meant by Friedel-Crafts acylation?

A

A reaction where any acyl group is put onto a benzene ring using an acyl chloride and an halogen carrier under anhydrous conditions. The resultant product is an phenylketone + HCl.

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27
Q

Give the general equation for Friedel- Crafts acylation

A

C6H6 + RCOCl → C6H5COR + HCl (Benzene) + (Acyl Chloride) → (Phenylketone) + (HCl)

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28
Q

Give all the details of a Friedel-Crafts acylation reaction

A

Reagents : An acyl chloride and an anhydrous halogen carrier Conditions: Reflux in the presence of an anhydrous halogen carrier. (CATALYST) Products: Phenylketone + Hydrochloric acid Electrophile: NO2+ Generation of electrophile: RCOCl + FeCl3 → FeCl4^- + R^+CO Regeneration of catalyst : H+ + FeCl4^- → FeCl3 + HCl

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29
Q

Give the general equation for the generation of the electrophile in a acylation reaction

A

RCOCl + FeCl3 → FeCl4^- + R^+CO

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30
Q

Give the general equation for the regeneration of the catalyst for acylation

A

H+ + FeCl4^- → FeCl3 + HCl

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31
Q

What is the friedel-crafts alkylation product naming system?

A

alkyl-benzene e.g. methylbenzene e.g. pentylbenzene

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32
Q

What is the friedel-crafts acylation product naming system?

A

Start: Phenyl Middle : Methan, ethan, propan etc. End: one E.g. phenylethanone E.g. phenylpentanone

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33
Q

Because friedel- crafts alkylation reactions result in a mixture of products, what can we do to overcome this problem?

A

Separate the products formed using fractional distillation or chromatography.

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34
Q

Explain the relative resistance to bromination of benzene compared to phenol and compared to cyclohexene

A
  • Benzene’s electrons are delocalised - Benzene is not strong enough to induce a dipole in Bromine so it needs a halogen carrier such as AlBr3 to aid in the reaction. - Benzene has a lower electron density than phenol. - Phenol has an additional lone pair incorporated from oxygen now it the benzene delocalised ring, making it more vulnerable to electrophilic attack - Cyclohexene’s electons are localised between 2 carbons. As electrophiles are strongly attracted to areas of high electron density, bromine will readily react with cyclohexene. - Final comment on most reactive to least reactive.
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35
Q

What are phenols?

A

Aromatic compounds with a hydroxy group (-OH) directly attached to the aromatic ring. They are WHITE CRYSTALLINE SOLIDS, smelling of disinfectant. They are weak acids (pH from 4-6)

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36
Q

What is the formula for phenol?

A

C6H5OH

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37
Q

Does phenol react with sodium hydroxide? Expand (Products, conditions, type of reaction?

A

Phenol reacts with sodium hydroxide solution at room temperature in a neutralisation reaction to from sodium phenoxide and water.

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38
Q

Why does phenol not react with carbonates?

A

Phenol is not a strong enough acid.

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39
Q

In the reaction between bromine water and phenol, what is produced?

A

2,4,6-tribromophenol.

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40
Q

Give 3 properties of 2,4,6-tribromophenol

A

White ppt Insoluble in water Smells of antiseptic.

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41
Q

When you add orange bromine water to phenol, what happens to the colour of the bromine water?

A

It decolourises

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42
Q

Describe the electrophilic substitution reaction of phenol with dilute nitric acid to form 2-nitrophenol

A

Reagents = Phenol + Dilute nitric acid Conditions = Room temp Products = 2-nitrophenol + water OR 4-nitrophenol + water

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43
Q

If your ever asked to give isomer of nitrophenol in the nitration of phenol, when you already have 2-nitrophenol and 4-nitrophenol, you give…

A

3-nitrophenol

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44
Q

Explain the relative ease of electrophilic substitution of phenol compared with benzene in terms of an electron pair donation from an oxygen p-orbiral in phenol

A

Phenol is more reactive than benzene. This is because, one of the lone pairs on the oxygen (from -OH) overlaps with the delocalised ring of electrons in the benzene, activating the ring. This means that the lone pair of electrons from the oxygen atom becomes PARTIALLY DELOCALISED into the pi-system. This increase the electron density of the ring, making it more likely to be attacked by electrophiles. Therefore, more reactive. For example, talk about different conditions for nitration and bromination for both benzene and phenol and compare the two.

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45
Q

What are electron donating groups?

A

Electron donating groups are groups that overlap with the delocalised ring of electrons and increase electron density at carbon number 2,4 and 6.

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46
Q

Give examples of electron donating groups

A

-OH -NH2

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47
Q

What are electron withdrawing groups?

A

Electron withdrawing groups are groups that don’t have any orbitals and can overlap with the delocalised ring an so it withdraws electron density at carbons 2,4,6

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48
Q

Because electron withdrawing groups, withdraw electron density at carbons 2,4 and 6, it means that…

A

electrons are unlikely to react at these positions and therefore when electrophilic substitution takes place, groups are directed towards the 3 or 5- position. NOTE: 3 and 5 are the same depending on which way you count your carbons.

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49
Q

What is the functional group of an aldehyde?

A

-CHO

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50
Q

What are aldehydes easily oxidised to?

A

Carboxylic acids

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51
Q

Why are aldehydes easily oxidised?

A

Aldehydes are easily oxidised because they have an hydrogen atom attached to the carbonyl [C=O] bond.

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52
Q

What does the name of aldehydes end in?

A

-al E.g. Ethanal E.g. Propanal

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53
Q

Where is the CHO functional group found on an atom?

A

At the END of the carbon chain.

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54
Q

What is the functional group of ketones?

A

-CCOC

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55
Q

Why are ketones not easily oxidised?

A

Lack of hydrogen attached to its functional group

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56
Q

What does the name of ketones end in?

A

-one E.g. Ethanone E.g. Propanone

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57
Q

Where is the CCOC functional group found on an atom

A

Anywhere BUT the end.

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58
Q

Is the carbonyl functional group polar? If so, why?

A

Yes it is this is because of the difference in electronegativity.

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59
Q

Why are aldehydes easily oxidised?

A

The hydrogen group on the carbon from the C=O bond allows for oxidation

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60
Q

Why are ketones not so easily oxidised?

A

Ketones don’t have a hydrogen atom attached to the C]O bond, so they are resistant to oxidation, ONLY strong oxidising agents like KMnO4 can oxidise ketones.

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61
Q

Describe the oxidation of aldehydes using acidified potassium dichromate to form carboxylic acids

A

Reaction name - Oxidation of an aldehyde Reagents - Oxidising agent and H2SO4 Conditions - Acidified conditions and reflux Products - Carboxylic acid + Water

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62
Q

When aldehydes are oxidised to a carboxylic acid, what is the colour change?

A

Orange to Green.

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63
Q

Give the balanced equation for the oxidation of an aldehyde to a carboylic acid

A

RCHO + [O] → RCOOH + H2O

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64
Q

What is meant by a nucleophile?

A

An electron pair donor.

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65
Q

Give two examples of nucleophiles

A

HCN and NaBH4

66
Q

What is meany by nucleophilic addition?

A

The addition of a nucleophilic species to a molecule.

67
Q

Describe the nucleophilic reaction of carbonyl compounds with NaBH4 to form alcohols.

A

Type of reaction; Reduction/Nucleophilic addition Reagents; Reducing agent (NaBH4) dissolved in water and methanol Conditions: Aqueous or alcoholic Products: Alcohol + hydroxide ion.

68
Q

Explain the reaction mechanism of nucleophilic substitution to form alcohols from carbonyl compounds

A

Step 1) The reducing agent (NaBH4) supplies hydride (H^-) which allow for the attack on the carbonyl group of an aldehyde or ketone. Step 2) The resultant intermediate is then dissolved in water and methanol forming an alcohol and a hydroxide ion. The negative oxygen forms a bond with a delta positive hydrogen from the water. The resultant product is an alcohol.

69
Q

Give the general reaction equation for ketones to alcohols

A

R’COR’’ + 2[H] → R’CHOHR’’ Ketone + Reducing agent → Secondary alcohol

70
Q

Give the general reaction equation for aldehydes to alcohols

A

RCHO + 2[H] → RCH2OH Aldehyde + Reducing agent → Primary alochol

71
Q

In the nucleophilic addition of a nucleophile to carbonyl groups, aldehydes go to primary alcohols whilst ketones go to….

A

Secondary alcohols

72
Q

In the nucleophilic addition of a nucleophile to carbonyl groups, ketones go to secondaru alcohols whilst aldehydes go to….

A

Primary alcohols

73
Q

Describe the nucleophilic addition reaction of carbonyls with HCN to form hydroxynitriles

A

Reaction name: Reduction/Nucleophilic addition Reagents: Reducing agent (HCN) in the presence of KCN Nucleophile : Cyanide ion (^-CN) Conditions: Product: Hydroxynitrile

74
Q

Explain the reaction mechanism of nucleophilic substitution to form hydroxynitriles from carbonyl compounds

A

Step 1) The CN^- ion attacks the slightly positive carbon atom and donates a pair of electrons to it. Both electrons from the double bond also transfer to the oxygen (heterolytic fission). Step 2) The H^+ (which comes from the dissociation of HCN) bonds to the oxygen to form the hydroxy group (OH)

75
Q

Give the general reaction equation for ketones to hydronitriles

A

R’COR’’ + HCN → R’COHR’CN E.g. CH3COCH3 + HCN → CH3OHCH3CN

76
Q

Give the general reaction equation for aldehydes to hydronitriles

A

RCHO + HCN → RCHOHCN

77
Q

In the nucleophilic addition of cyanide to carbonyl compounds, why ate the conditions acidified?

A

The conditions are acidified because it allow the cyanide ions to react directly with the carbonyl by making it more reactive as the polarity of the C=O bond is increased.

78
Q

Why may we decide to use NaCN rather than HCN at times?

A

HCN is a toxic gas. Note: When using NaCN, we still use a fume cupboard.to prevent further risk.

79
Q

What do we use to test for the aldehyde and ketone functional group?

A

2,4-DNP (Brady’s reagent)

80
Q

For Brady’s reagent to give a positive test, it must be dissolved in….

A

Water and methanol

81
Q

if Brady’s reagent reacts with an aldehyde or ketone, what will happen?

A

A bright ORANGE precipitate will form.

82
Q

What can Brady’s reagent not be used on?

A

Everything else but aldehydes and ketones Especially - Carboxylic acids.

83
Q

After obtaining our bright orange ppt from the Brady’s reagent test, how can we identify the specific aldehyde/ketone?

A

Collect the ppt using filtration Purify the ppt using re-crystallisation Dry. Place in a melting point machine After drying, measure the melting point and compare to to values from a TRUSTED SOURCE.

84
Q

Some ketones have very similar boiling points, how can we identify the ketone from a set of possibilities?

A

Use the melting points of their Brady’s reagent derivatives

85
Q

What is Tollen’s reagent (ammonicial silver nitrate)

A

A weak oxidising agent.

86
Q

How do we make Tollens’ reagent?

A

Step1) Sodium hydroxide solution is added to silver nitrate solution until a brown ppt appears. Step2) Dilute ammonia is added drop-wise until the brown ppt redissolves.

87
Q

What does Tollen’s reagent do?

A

It allows us to distinguish between an aldehyde and a ketone.

88
Q

How does it help us distinguish between an aldehyde and a ketone?

A

It uses the fact that an aldehyde can be easily oxidised by a weak oxidising agent whilst ketones can’t.

89
Q

What’s observation can you make when tollen’s reagent is heated together with an aldehyde in a test tube?

A

Silver mirror

90
Q

When Tollen’s reagent reacts with an aldehyde, what is oxidised?

A

The aldehyde, from an aldehyde to a carboxylic acid.

91
Q

When Tollen’s reagent reacts with an aldehyde, what is reduced?

A

The silver ions in Tollen’s reagent. The resultant reaction causes a silver mirror to form.

92
Q

If Tollen’s reagent is used on a ketone, what happens and why

A

There will be NO reaction. This is because Tollen’s reagent is not a strong enough oxidising agent to further oxidise ketones.

93
Q

Give the generic reaction of an aldehyde reacting with Tollen’s reagent

A

RCHO +[O] → RCOOH Aldehyde + Oxidising agent → Carboxylic acid

94
Q

Why does a silver mirror form when Tollen’s reagent reacts with an aldehyde?

A

A silver mirror forms because the silver ions from the Tollen’s reagent are reduced.

95
Q

Give the equation to show the silver ions in Tollen’s reagent being reduced

A

Ag(NH3)2^+ + e^- → Ag (s) + 2NH3 Tollen’s reagent + electron → Silver + Ammonia

96
Q

What functional group does carboxylic acids contain?

A

-COOH

97
Q

What do all carboxylic end in?

A

-oic acid

98
Q

In terms of the carbon chain, where is the carboxylic acid always found?

A

At the end of the chain

99
Q

When naming carboxylic acids, which carbon do we start from?

A

The carbon of the carboxylic acid

100
Q

What type of bonds does carboxylic acid form with water?

A

Hydrogen bonds.

101
Q

Explain the solubility of carboxylic acids

A

Carboxylic acids are polar molecules. The polarity of carboxylic acids is mainly due to the carbonyl bond. At the carbonyl bond, there is a huge difference in electronegativity. This difference in electronegativity allows for the formation of hydrogen bonds between carboxylic acids and water. Hydrogen bonds are able to form between the highly polarised, delta positive ion from water ad the delta negative oxygen ion from the carboxylic acid. This makes carboxylic acids very soluble in water.

102
Q

When showing hydrogen bonds, we must also show:

A

Lone pairs on the oxygen Dipoles H bonds using dotted lines

103
Q

As the chain length of carboxylic acids increases, does the solubility do the same? Explain your answer.

A

As the chain length of the carboxylic acids increases, solubility decreases. This is because the majority of the carboxylic acid is non-polar and therefore, forms less H bonds with water. Therefore, solubility decreases as chain length increases,

104
Q

Describe the reaction between a carboxylic acid and a metal

A

Carboxylic acids react with the most reactive metals in a REDOX reaction to form a salt and hydrogen gas.→ ⇄ Generic equation : Carboxylic acid + Metal → Salt + Hydrogen gas

105
Q

Carboxylic acid + Metal →

A

Salt + Hydrogen gas

106
Q

When carboxylic acids react with metals/metal oxides/metal hydroxide/metal carbonates, the name of the salt in a generic form is?

A

Metal - carbon chain derivative - oate e.g. Barium butanoate

107
Q

Describe the reaction between a carboxylic acid and a metal oxide

A

Carboxylic acids react with metal oxides to form a salt and water Carboxylic acid + Metal oxide → Salt + Water

108
Q

Carboxylic acid + Metal oxide →

A

Salt + Water

109
Q

Describe the reaction between a carboxylic acid and a metal hydroixde

A

Carboxylic acids react with metal hydroixdes to form a salt and water Carboxylic acid + Metal hydroxide → Salt + Water

110
Q

Carboxylic acid + Metal hydroxide →

A

Salt + Water

111
Q

Describe the reaction between a carboxylic acid and a metal carbonate

A

Carboxylic acids react with meta carbonates to produce a salt, water and carbon dioxide. Carboxylic acid + Metal carbonate → Salt + Water + Carbon dioxide

112
Q

Carboxylic acid + Metal carbonate →

A

Salt + Water + Carbon dioxide

113
Q

What is the functional group of esters?

A

-COO

114
Q

What are the uses of esters?

A
  • Flavouring food - Solvents -Plasticiser to make polymers flexible.
115
Q

Name the 3 ways in which, we can make esters

A

1) Alcohol + Carboxylic acid 2) Alcohol + Acid anhydride 3) Alcohol + Acyl chloride

116
Q

Give details of esterification (alcohols + carboxylic acids)

A

Reaction name - Esterfication Reagents - Alcohol + concentrated sulfuric acid + carboxylic acid Catalyst : Conc H2SO4 Condtions: Reflux Product: Ester + Water

117
Q

Give the generic equation of esterification using an alcohol + carboxylic acid

A

Alcohol + Carboxylic acid ⇄ Ester + Water

118
Q

CH3COOH + CH3OH ⇄

A

CH3COOCH3

119
Q

In esterification, what group loses what?

A

Alcohols loses H Carboxylic acids loses OH

120
Q

How do we name esters?

A

Alcohol derivative first Carboxylic acid derivative next (STEM) Ending over - oate

121
Q

Name the following esters: CH3CH2COOCH2CH3 CH3CH2CH2CH2COOCH3

A

Ethyl propanoate Methyl pentanoate

122
Q

In esterification, when using small esters, what do we do and why?

A

We distil off the ester because it’s more volatile than other compounds

123
Q

In esterification, when using small esters, what do we do and why?

A

This esters are harder to form so it’s best to heat them under REFLUX and use FRACTIONAL DISTILLATIN to separate the ester from other compounds

124
Q

What is an acid anhydride?

A

An acid anhydride is an acid derivative that is MORE REACTIVE than a siimiliar carboxylic acid. It is made by the removal of a water molecule from two carboxylic acids

125
Q

How are acid anhydride made?

A

They are made by the removal of a water molecule from two carboxylic acids

126
Q

How can we make esters using acid anydrides, give all details

A

Reaction Name: Esterification via acid anhydrides Reagents: Acid anhydride + Alcohol Conditions: Reflux under dry conditions General equations : Acid anhydride + Alcohol → Ester + Carboxylic acid

127
Q

Acid anhydride + Alcohol →

A

Ester + Carboxylic acid

128
Q

Acid anhydrides will have the _____ starting name as the carboxylic acid formed

A

Same

129
Q

How can we figure out the name of an acid anhydride?

A

Count the number of carbons before encountering the C-O bond. Then call it: Carbon stem derivative - oic - anhydride

130
Q

If propanoic acid was combined to form an acid anhydride, it will be called?

A

Propanoic anhydride

131
Q

What meant by the acidic hydrolysis of esters?

A

This refers to the breaking down of an ester in acidified conditions using water under reflux.

132
Q

Give the generic equation for the acidic hydrolysis of an ester

A

Ester + Water + (H^+) + (Reflux) ⇄ Alcohol + Carboxylic acid

133
Q

In the acidic hydrolysis of an ester, what products are formed?

A

Alcohol + Carboxylic acid

134
Q

Give all the details of the acidic hydrolysis of esters

A

Reagents: Ester, water, dilute acid (usually HCl or H2SO4. Conditions: Acidified, Reflux, high temp Products: Alcohol + Carboxylic acid

135
Q

In the acidic hydrolysis of an ester, what group gains what?

A

Carboxylic acids gain OH Alcohols gain H

136
Q

What meant by the basic hydrolysis of esters?

A

This refers to when an ester is broken down through the use of reflux, a dilute alkali and alkaline conditions

137
Q

Give the generic equation for the basic hydrolysis of an ester

A

Ester + Dilute alkali+ (Reflux) ⇄ Alcohol + Carboxylate salt

138
Q

In the acidic hydrolysis of an ester, what products are formed?

A

Alcohol + Carboxylate salt

139
Q

Give all the details of the basic hydrolysis of esters

A

Reagents : Ester, dilute alkali Conditions: Alkaline, reflux, high temp Products: Carboxylate salt + Alcohol

140
Q

What is a carboxylate salt?

A

A derivative of carboxylic acid but the COOH group is actually COO^-(any metal) e.g. COO^-Na

141
Q

In the basic hydrolysis of an ester, what group gains what?

A

The carboxylic acid sides gets the metal oxide to form a carboxylate salt The alcohol part gets the H

142
Q

How are acyl chlorides formed?

A

By reacting carboxylic acids with thinoyl chloride (SOCl2)

143
Q

What is the functional group of acyl chlorides?

A

-COCl

144
Q

What is the general formula of acyl chlorides?

A

CnH2n-1OCl

145
Q

What does the name of all acyl chlorides end in?

A

-oyl chloride

146
Q

Where do acyl chlorides appear on the carbon chain?

A

at the END

147
Q

Give all the details for the preparation of acyl chlorides

A

Acyl chlorides are made by reacting a carboxylic acid with thionyl chloride. The -OH group from the carboxylic acid is replaced with the -Cl group from the thionyl chloride (SOCl2) . The reaction also produces HCl (g) + SO2 (g)

148
Q

How can we separate the acyl chloride from SO2(g) and HCl(g) ?

A

Use distillation

149
Q

Carboxylic acid + SOCl2 (thionyl chloride) →

A

Acyl chloride + SO2 (g) + HCl(g)

150
Q

Give uses of acyl chlorides

A

They can react with alcohols to form an ester They can react with water to form a carboxylic acid They can react with ammonia to form a primary amine They can react with a primary amine to form a secondary amine.

151
Q

What type of reaction is the reactions between an acyl chloride and alcohol/water/ammonia/primary amine are all

A

Nucleophilic substitution reactions

152
Q

When an acyl chloride reacts with water what happens?

A

A vigorous reaction occurs producing a carboxylic acid and HCl.

153
Q

Acyl chloride + Water →

A

Carboxylic acid + HCl

154
Q

When an acyl chloride reacts with an alcohol what happens?

A

A vigorous reaction at RT occurs, producing an ester and HCl.

155
Q

Acyl chloride + Alcohol →

A

Ester + HCl → ⇄

156
Q

Why does Acyl chloride + Alcohol give a higher yield than an alcohol + carboxylic acid in terms of producing an ester?

A

Acyl chloride + alcohol → IRREVERSIBLE REACTION Carboxylic acid + alcohol ⇄ REVERSIBLE REACTION

157
Q

When an acyl chloride reacts with ammonia what happens?

A

A violent reaction at RT producing a primary amine Observation : White smoke

158
Q

Acyl chloride + Ammonia →

A

Primary amine + HCl

159
Q

When an acyl chloride reacts with a primary amine what happens?

A

A violent reaction at RT producing a secondary amine.

160
Q

Acyl chloride + Ammonia →

A

Secondary amine + HCl

161
Q

Acyl chloride + (2xAmmonia) →

A

Secondary amine + Ammonium chloride

OCR A Chemistry (16 decks)

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