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A Level - Chemistry > 18: Further Organic Chemistry > Flashcards

18: Further Organic Chemistry Flashcards

1
Q

What is an arene?

A

Aromatic hydrocarbons

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2
Q

What are the two structures of benzene?

A

Kekulé and delocalised structure

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3
Q

What is the molecular formula of benzene?

A

C6H6

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4
Q

What is the structure of benzene?

A

C6H6 Planar molecule containing a ring of six carbons each with a H attached

Hexagon shape

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5
Q

What is notable about the bonds in benzene?

A

All bonds are the same length

Inbetween length of single and double bond

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6
Q

Where are the electrons in benzene?

A

Delocalised above and below the plane of the ring

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7
Q

What does the delocalisation do to benzene?

A

Increases the stability of the molecule

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8
Q

What is the Kekulé structure of benzene?

A

Alternating single and double bonds in a hexagon structure

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9
Q

What does the bond length suggest about the structure?

A

Kekulé model suggests 2 different bond lengths

Therefore suggests delocalsied structure

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10
Q

How was the bond length in benzene found?

A

X-ray diffraction

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11
Q

What are the bond angles in benzene?

A

120°

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12
Q

What is the structure of the delocalised model of benzene?

A

Each carbon forms three σ bonds (2C 1H) p-orbital remaning is above and below plane of ring which overlap sideways to form ring of π-bonds which are delocalised

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13
Q

Where are delocalised electrons in benzene?

A

Two ring-shaped clouds above and below plane of the carbons

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14
Q

What is the length of bonds in the delocalised structure?

A

All the bonds are the same length

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15
Q

Why are electrons delocalised in the delocalised structure of benzene?

A

Electrons do not belong to a specific atom

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16
Q

What is the enthalpy change of hydrogenation?

A

Enthalpy change of the reaction whereby hydrogen gas is added across a C=C

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17
Q

How do hydrogenation enthalpies disprove the Kekulé structure?

A

Cyclohexene with 1 double bond has -120 kJ/mol

Kekulé structure would expect to have -360 kJ/mol

However experimental value is -208 kJ/mol

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18
Q

Why is the enthalpy of hydrogenation of benzene less negative that expected?

A

More energy needed to break the bonds than expected in the Kekulé

More stable than Kekulé due to delocalised ring of electrons

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19
Q

What was used to compare the structures of benzene?

A

X-ray diffraction

IR spectra for bonds present

Enthalpy of hydrogenation

Whether follows standard electrophillic addition

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20
Q

What occurs when bromine water is added to benzene?

A

No colour change seen

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21
Q

Why does benzene not undergo addition reactions?

A

Delocalised π-bonds mean addition would decrease stability

Spread out negative charge rather than one area of high electron density, doesn’t attract electrophiles as much

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22
Q

What is the equation of benzene burning in air?

A

2C6H6 + 15O2 → 12CO2 + 6H2O

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23
Q

What occurs when benzene is burnt in air?

A

Very smoky flame - too little to burn benzene completely

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24
Q

What is the preffix of NO2?

A

nitro-

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25
Q

What is the name of a benzene ring with an -OH group on one of the carbons?

A

Phenol

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26
Q

What is the name of a benzene ring with a -NH2 substituent?

A

Phenylamine

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27
Q

How are benzene compounds named when there are more than one group added?

A

If all are same, pick group to start which gives smallest numbers when counting round

If groups are different, start from molecule which gives it the suffix and count round to give smallest numbers

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28
Q

What is the name of benzene with a single -CH3 group bonded?

A

Methylbenzene or Toluene

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29
Q

What is the prefix of bezene when it is bond to another compound?

A

Phenyl-

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30
Q

State the reactivity of benzene compared to alkene

A

Stability of delocalised electrons in ring means it is less reactive

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31
Q

Why does benzene have a sootier flame?

A

High C:H

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32
Q

What are the coniditons for the hydrogenation of benzene?

A

Raney nickle catalyst

200°C

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33
Q

What type of reaction does benzene undergo with electrophiles?

A

Electrophilic substitution

NOT addition

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34
Q

What is the mechanism for the electrophilic substitution reaction?

A

Benzene delocalised ring reacts with electrophile, breaks ring (arrow from ring to E+)
An unstable intermediate forms (ring stops either side of carbon, replace by +, show E and H bonded to carbon and arrow from C-H to +)

H+ is lost, delocalised ring is reformed

E = electrophile

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35
Q

What is an electron withdrawing group?

A

Group that draws electron density from neighboroughing atoms to itself

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36
Q

What is an electron donating group?

A

Group which donates electrons into a delocalised structure

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37
Q

List some common electron withdrawing groups

A

NO2, CO2, ester

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38
Q

List some electron donating groups

A

OH, NH2

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39
Q

Why can benzene only react with very positively charged species?

A

Electrons are spread and in a low-density

Therefore high + charge needed for the ring to attack

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40
Q

What can be used to make stronger electrophiles?

A

Halogen carrier

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41
Q

How does a halogen carrier work?

A

Accepts a lone pair of electrons from a halogen atom in halogenoalkane or X2

Lone pair is pulled away, polarisation in molecule increases and sometimes carbocation / X+ forms

Makes the electrophile stronger

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42
Q

Name the standard halogen carriers

A

Aluminium halides

Iron halides

Iron

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43
Q

What are the conditions for the bromination of benzene?

A

Anhydrous iron/iron (III) bromide catalyst

Dry benzene and liquid bromine

Warmed

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44
Q

What does a halogen carrier do in a bromination reaction?

A

Breaks Br2 to Br+ and FeBr4

Ring attacks Br+

Electrons form C-H goes into ring and Fe-Br electrons go to the lost H

Forms bromobenzene + HBr + FeBr3

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45
Q

What are the reactions for the bromination of benzene?

A

FeBr3 + Br2 → [FeBr4]- + Br+

C6H6 + Br+→ C6H5Br + H+

H+ + [FeBr4]- → FeBr3 + HBr

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46
Q

What is alkylation?

A

Addition of an alkyl group (e.g. methyl, ethyl etc.) onto the benzene ring

Generally uses a Friedel-Crafts reaction

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47
Q

What are Friedel-Crafts reactions used for?

A

Forms C-C bonds

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48
Q

What are the conditions and reagents for a alkylation reaction?

A

Benzene + halogenoalkane

Anhydrous AlCl3 catalyst

Reflux

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49
Q

What occurs when a chloroalkane reacts with AlCl3 in a Friedel-Crafts reaction?

A

R-Cl + AlCl3 → R+ + [AlCl4]-

Cl lone pair attacks Al and R-Cl breaks

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50
Q

What are the stages in an alkylation Friedel-Crafts reaction?

A

R-X + AlCl3 → R+ + [AlCl3X]-

C6H6 + R+ → C6H5R + H+

H+ + [AlCl3X]- → HX + AlCl3

Overall: C6H6 + R-X → C6H5R + HX

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51
Q

What is an acylation reaction?

A

Addtion of an acyl group (RC=O) onto a benzene ring

This is a Friedel-Crafts reaction

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52
Q

What are the reagents and conditions for an acylation?

A

Dry acyl chloride and benzene

Anhydrous AlCl3

Reflux

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53
Q

What is the overall reaction in an acylation reaction?

A

C6H6 + RC=OCl → C6H5RC=O + HCl

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54
Q

What are the stages of reactions in the acylation Frieldel-Crafts reaction?

A

RCOCl + AlCl3 → RC+=O + [AlCl4]-

C6H6 + RC+=O → C6H5COR + H+

H+ + [AlCl4]- → HCl + AlCl3

Overall: C6H6 + RCOCl → C6H5COR + HCl

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55
Q

What is nitration of benzene?

A

NO2 is added to a benzene ring

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56
Q

What are the conditions of the nitration of benzene?

A

conc H2SO4 + conc HNO3

50°C for benzene

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57
Q

Which electrophile is used for the nitration of benzene?

A

NO2+

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58
Q

What is the name of the NO2+ ion?

A

Nitronium ion

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59
Q

How is the nitronium ion produced for the benzene substitution?

A

HNO3 + H2SO4 → H2NO3+ + HSO4-

H2NO3+ → NO2+ + H2O

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60
Q

What is the overall reaction between the nitronium ion and benzene?

A

C6H6 + HNO3 → C6H5NO2 + H2O

H2SO4 not included as it is a catalyst

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61
Q

Why are temperatures not above 50C reccomended for the nitration of benzene?

A

Temperatures not above that as it causes more than 1 nitration

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62
Q

What is the molecular formula of phenol?

A

C6H5OH

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63
Q

How likely is phenol to undergo electrophilic substitution compared to benzene?

A

Phenol is more likely to undero electrophilic substitution than benzene

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64
Q

Why is phenol more likely to undergo electrophilic substitution?

A

Lone pair in p-orbital of oxygen overlaps with π-bonds in benzene ring

Lone pair from oxygen is partially delocalised into π-system

Increases electron density in ring so more lilkely to be attacked by electrophiles

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65
Q

What occurs when phenol is added to bromine water?

A

Bromine water is decolourised

Occurs as phenol is more reactive than benzene

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66
Q

What is the solubility of ethanol and phenol in water?

A

Phenol - slightly soluble

Ethanol - highly soluble

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67
Q

What is the pH of ethanol and phenol?

A

Ethanol - neutral

Phenol - 4-5

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68
Q

How does phenol react with NaOH?

A

C6H5OH + NaOH → Na+ C6H5O- + H2O

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69
Q

What are the procedure for the production of aspirin?

A

Salicyclic acid + Ethanoic anhydride + Phosphoric acid

Warm to 50°C for 15 minutes then cool on ice, forms aspirin crystals

Filter crystals under reduced pressure

Recrystallise the aspirin in a mix of water and ethanol

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70
Q

What is the reaction to form aspirin?

A

Salicyclic acid + ethanoic anhydride → Aspirin + ethanoic acid

C7H6O3 + C4H6O3 → C9H8O4 + CH3COOH

Look at the structural formula

71
Q

How does phenol react with ethanoic anhydride?

A

Esterification reaction

72
Q

Why is ethanoic anhydride somtimes used instead of an acyl chloride?

A

Reacts in the same way

Cheaper and safer as not as reactive

73
Q

What is the molecular formula of phenylamine?

74
Q

What is an amine?

A

Compound where a hydrogen in ammonia is replaced by R

Amines contain functional group -NR2 (alkyl or H)

75
Q

What are the types of amines?

A

Primary

Secondary

Tertiary

Quaternary

76
Q

What does aliphatic mean?

A

Compounds without any benzene ring structures

77
Q

What type of amine is phenylamine?

A

Primary amine - only one of hydrogens replaced by organic group

78
Q

What gives phenylamine its unique properties?

A

Free electrons on nitrogen are donated/delocaised into the ring system

Therefore acts differently to typical amines

79
Q

Is NH2 an electron donating or withdrawing group?

A

Electron donating group

80
Q

How reactive is phenylamine compared to benzene and why?

A

Phenylamine is more reactive than benzene

Nitrogen’s lone pair increases electron density around the ring

Therefore attacks electrophile better

81
Q

What are the stages of the production of phenylamine from benzene?

A

Nitration of benzene

Reduction of nitro group to amine

82
Q

How is nitrobenzene converted to phenylamine?

A

Nitrobenzene, tin and conc hydrochloric acid mixed

Heated under reflux at 100°C

Cooled and excess NaOH added

Steam distillation of mix and then separation from water using brine and drying agent added (anhydrous potassium carbonate)

Purified by distillation

83
Q

What are the conditions for reducing nitrobenzene?

A

1) Reflux mix of nitrobenzene, tin andconc hydrochloric acid
2) NaOH added

84
Q

Why is phenylamine slightly soluble in water?

A

Can form hydrogen bonds

Benzene breaks more H-bonds than formed betwen water and NH2

85
Q

Why is phenylamine less water soluble than phenyl ammonium salt?

A

Ammonium salt is ionic/charged, phenylamine is not

Lone pair on N in phenylamine is delocalisde into ring system

86
Q

What is a test for phenol?

A

Reacting phenol with FeCl3 forms a purple solution

87
Q

What is used as an alternative to phenol and why?

A

methyl 4-hydroxybenzoate

Reacts similarly but it is less dangerous

88
Q

What is the purpose of the Grignard reaction?

A

Reaction to extend the carbon chain

89
Q

What are the conditions of producing the species for the Grignard reaction?

A

Dry ether

R-I (iodine)
Mg

90
Q

What is the species which is made for the Grignard reaction?

91
Q

What occurs when a Grignard reactant is used to react with carbon dioxide?

A

Produces carboxylic acid

CO2 + -R → R-COOH

92
Q

How are amines typically made?

A

Heating a halogenoalkane with excess ethanolic ammonia

93
Q

What is the problem with heating a halogenoalkane with excess ethanolic ammonia?

A

Produces mix of primary, secondary and tertiary amines and quaternary ammonium salts

94
Q

Why is there a mix when you heat a halogenoalkane with excess ethanolic ammonia?

A

Lone pair of electrons on the amine

Acts as a nucleophile for nucleophilic substitution with any halogenoalkane causes substituted amines to be produced

95
Q

How many hydrogens and R groups are on a primary amine?

A

2 hydrogens

1 R group

96
Q

How many hydrogens and R groups are on a secondary amine?

A

1 hydrogen

2 R groups

97
Q

How many hydrogens and R groups are on a tertiary amine?

A

3 R groups

98
Q

How do you name secondary amines such as C2H5-NH(CH3)?

A

N-methylethylamine

N-smaller chain then followed by longer name

99
Q

Which group takes priority in naming amino acids?

A

Acid group has higher priority so forms suffix

Amino groups are relegated to a prefix

100
Q

How polar is the N-H bond?

A

Polar but not as polar as OH bond

101
Q

How soluble are amines?

A

Smaller amines are soluble as they are polar and N-H can form hydrogen bonds

Larger ones cannot as they disrupt too many H-bonds

102
Q

What occurs to amines in water?

A

R-NH2 + H2O → R-NH3+ + OH-

Therefore becomes alkaline

103
Q

What is the smell of amines?

A

“Fishy” smell

104
Q

What are amines in the Bronsted-Lowry theory?

A

Bronsted-Lowry bases

Proton acceptors

105
Q

What does the ability of an amine to act as a base depend on?

A

Availability of lone pair on N atom to accept H+

Increased electron density of lone pair on N means it is a stronger base

106
Q

How are the different amines ordered in strength of base from low to high?

A

Aromatic → primary → secondary → tertiary

107
Q

Why are amines more basic the more R groups bound to it?

A

Inductive effect of alkyl groups means it pushes electron density towards the nitrogen

The higher the electron density of the lone pair on the N, the stronger the base

108
Q

Why are aromatic amines less basic?

A

Lone pair on N partially delocalised into benzene ring

Reduces electrons on N atom, and therefore less likely to offer to H+ so it is a weaker base

109
Q

What is the most common way for producing an amine?

A

Producing a nitrile from a halogenoalkane

Reducing to an amine

110
Q

What are the methods reducing nitriles to amines?

A

LiAlH4 in dry ether followed by dilute acid

Nickle catalyst, hydrogen, high temp and pressure

111
Q

Why is LiAlH4 not used in industry?

A

Too expensive for industry

V reactive with any water

112
Q

Why are amines nucleophiles and therefore how can they react?

A

Lone pair of electrons

Nucleophilic substitution reaction

113
Q

How do amines react with acids?

A

R-NH2 + HA → R-NH3+ A-

114
Q

What is the colour of the [Cu(H2O)6]2+ complex?

115
Q

What is a test for amines?

A

Add small amount of amine to copper(II) sulphate solution

Pale blue precipitate forms

XS amine gives a deep blue solution

116
Q

What do amines do to copper (II) sulphate?

A

Amine acts as base,deprotonates H2O to OH-

Forms [Cu(OH)2(H2O)4] which is an insoluble pale blue precipitate

More amine replaces ligand to form deep blue [Cu(R-NH2)4(H2O)2]2+

117
Q

How do primary amines react with acyl chlorides?

A

Forms a secondary amide

118
Q

What are the requirments for reacting acyl chlorides with amines?

A

Concentrated solution of amine

119
Q

What is observed when an amine reacts with an acyl chloride?

A

Violent reaction occurs

Produces a solid, white mixture

120
Q

What do amides contain?

A

Functional group -CONH2

121
Q

Why do amides react differently than amines?

A

Carbonyl pulls electrons away from the rest of the group

122
Q

What types of amides are there?

A

Primary amides

N-substituted amides depending on number of carbonds the nitrogen is bonded to

123
Q

What is the suffic of amide?

124
Q

How are N-substituted amides named?

A

N-alkyl-

then -amide

125
Q

How can amides be made?

A

Reacting acyl chloride with amnmonia or a primary amine

126
Q

What are the conditions for producing amides?

A

Acyl chlride + conc ammonia or primary amine

Room temp

127
Q

What is condensation polymerisation?

A

Monomers being joined together with the loss of a small molecule

128
Q

What do monomers have to contain for condensation polymerisation?

A

At least two functional groups

Normally involves two differents types of monomer
Each reacts with group on another monomer to form a bond

129
Q

What are amide links?

A

-CONH- which forms between a carboxlyic acid and amino groups

Water lost each time one forms

130
Q

What are polyamides?

A

Monomers are usually dicarboxylic acids and diamines

Forms -CONH- links

Water lost each time it forms - condensation reaction

131
Q

What is an amino acid?

A

Molecule that has amino group (NH2) and carbocxyl group (COOH)

132
Q

What is the structure of amino acids?

A

H2N - CH(R) - COOH

R is different based on the amino acid

133
Q

What does amphoteric mean?

A

Molecule which is able to act as an acid and a base

134
Q

How are amino acids amphoteric?

A

Amino groups can act as a base

Carboxyl (COOH) group can act as an acid

135
Q

What is a zwitteron?

A

Overall neutral molecule with both positive and negative charges in different parts of the molecule

136
Q

What is the isoelectric point?

A

pH when the overall charge on a molecule is zero

137
Q

When can amino acids act as zwitterions?

A

Isoelectric point

This depends on the R group

138
Q

What occurs to amino acids in more acidic than isoeletric point conditions?

A

NH2 group is protonated to NH3+

139
Q

What occurs to amino acids in more basic conditions than the isoleletric point?

A

COOH group is deprotonated to COO-

140
Q

What is the composition of a zwitterion of an amino acid?

A

Amino group protonated NH2→ NH3+

Carboxyl group deprotonated COOH → COO-

141
Q

When will amino acids have their isoeletric point at around pH 7 ?

A

When there are the same number of carboxyl and amino groups

142
Q

What are the amino acids found in nature?

A

2-amino acids (amino group on the second carbon, first is carboxyl)

143
Q

What groups are attached to the second carbon of a 2-amino acid?

A

Carboxyl (COOH)

Amino (NH2)

Hydrogen atom

R group

144
Q

Which amino acid has a hydrogen atom as the R group?

145
Q

What is the optical activity of 2-amino acids?

A

Chiral molecules

Chiral centre on 2nd carbon

146
Q

What occurs to plane-polarised, monochromatic light if it shone through an aqeuous solution of one enantiomer of a 2-amino acid?

A

Plane of the light gets rotated because of the chiral carbon

147
Q

What is the exception to the chirality of 2-amino acids?

A

Glycine

R group is hydrogen so no chiral centre

148
Q

What does achiral mean?

A

Not a chiral molecule

149
Q

What are proteins?

A

Polymers of amino acids

Condensation polymers

150
Q

What are the links which form between amino acids in proteins?

A

Peptide links

Same as amide links

151
Q

How does a peptide link form?

A

Carboxyl group of one amino acid reacts with amino group of adjacent one

One water lost - Condensation reaction

152
Q

How are proteins hydrolysed?

A

Hot aqueous HCl needed

Produces ammonium salts of amino acids which is then neutralised using a base

153
Q

Why would you want to hydrolyse proteins?

A

Break into constiutent amino acids

Allows for identification of amino acids which make up a protein

154
Q

What are polyesters?

A

Polymers formed between dicarboxlyic acid and diol monomers

Condensation polymers

155
Q

What links form between dicarboxylic acids and diols?

A

Ester links

156
Q

How do you find the monomers of a polyester from the repeat unit?

A

Break ester link between C - O

Add H or OH to both ends to find the monomers

157
Q

How can unknown amino acids be identified?

A

Paper chromatography

158
Q

Why is phenol more reactive than benzene?

A

Oxygen donates electron to the delocalised ring system

Occurs as Oxygen has lone pairs which overlap in same plane

Increases negative charge of teh ring so acts as a better nucleophile

159
Q

What is the Rf Value?

A

Rf value = distance travelled by spot / distance travelled by solvent

160
Q

What is the procedure of paper chromatography to determine unkown amino acids?

A

Draw pencil line near bottom of chromatography paper and put a conc spot of mix

Place paper in small beaker with small amount of solvent below spot of mixture with watch glass on top of beaker

When solvent is near the top take out of the solution

Spray with ninhydrin solutin or put in jar with iodine crystals, and circle positions

Calculate Rf and compare with known values

161
Q

Why do amino acids move different amounts on the chromatography paper?

A

Different amino acids have different solubilities in the solvent

Therefore move at different rates so they separate

162
Q

What is the solvent front?

A

Distance moved by the solvent

163
Q

How are amino acids shown on paper chromatograms?

A

Ninhydrin solution

Dip into jar with iodine crystals, then circle positions with a pencil

164
Q

When can you compare the Rf values for the amino acids?

A

Experiment done under standard conditions

165
Q

What can be done other than paper chromatography to identify amino acids?

A

Thin-layer chromatography

166
Q

What is the general formula of a Grignard reagent?

A

R-Mg-X
Where X is a halogen (usually iodine)

167
Q

How are Grignard reagents made?

A

R-X + Mg → R-MgX

Reflux

Dry ether

168
Q

How are carboxylic acids made using the grignard reaction?

A

Bubble CO2 through Grignard reagent in dry ether

Add dilute acid such as hydrochloric

169
Q

How does the Grignard reagent form bonds with CO2?

A

new C-C bond forms between carbon in CO2 and C-Mg carbon in Grignard reagent

One of C=O bonds in CO2 broken to form -COO- which is protonated by the acid

170
Q

How are alcohols made from aldehydes and ketones by the Grignard reaction?

A

new C-C bond forms between C in C-Mg and C=O carbon in the carbonyl

Causes C=O to break and forms -OH

171
Q

What is the procedure for making an alcohol from a ketone/aldehyde by the Grignard?

A

Carbonyl compound added to the Grignard reagent in dry ether

Dilute acid is then added

172
Q

What type of alcohol is formed in the Grignard reagent reacting with an aldehyde or ketone?

A

Aldehyde - secondary alcohol

Ketone - tertiary alcohol

173
Q

Why is the pH of phenol slightly acidic?

A

Phenoxide ion - C6H5O-

This ion is stable due to the delocalisation of the lone pair

Therefore dissociates more readily in water

A Level - Chemistry (26 decks)

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