Module 6 Flashcards
(225 cards)
1
Q
Benzene is a carcinogen, what does this mean? (1 mark)
A
It causes cancer.
2
Q
What is the prefix of benzene? (1 mark)
A
phenyl
3
Q
Describe the Kekulé model of benzene. (2 marks)
A
Six carbon ring with alternate single and double bonds.
4
Q
Explain how the lack of reactivity of benzene disproves Kekulé’s model of benzene. (3 marks)
A
Benzene should descolourise bromine water if it contains carbon double bonds.
However:
Benzene does not undergo electrophilic addition reactions.
Benzene does not decolourise bromine under normal conditions.
5
Q
Explain how the lengths of the carbon-carbon bonds in benzene disprove Kekulé’s model of benzene. (2 marks)
A
All the bonds in benzene are the same length, between the lengths of a single and double bond.
6
Q
How were the carbon-carbon bonds in benzene measured? (1 mark)
A
Using X-ray diffraction
7
Q
Explain how hydrogenation enthalpies can be used to disprove Kekulé’s model of benzene. (3 marks)
A
The expected enthalpy change of hydrogenation is 3 times that of cyclohexene (as it has 1 double bond and benzene has 3).
In reality, the hydrogenation of benzene is lower than expected.
This means that benzene is more stable than the Kekulé model suggests.
8
Q
Describe the delocalised model of benzene. (2 marks)
A
Each carbon atom has one electron in a p-orbital.
There is a delocalised pi-electron density above and below the plan of benzene ring.
9
Q
How are the rings of electron density formed above and below the benzene ring plane? (1 mark)
A
Adjacent p-orbital electrons overlap sideways.
10
Q
What does it mean if benzene is monosubstituted? (1 mark)
A
Only one hydrogen in benzene has been substituted for a different atom/group.
11
Q
When is the prefix for benzene used? (1 mark)
A
When benzene is attached to a carbon chain of 7 or more.
When it is attached to an alkyl chain with a functional group.
12
Q
Name three exceptions to naming aromatic compounds. (3 marks)
A
Benzoic acid
Phenylamine
Benzaldehyde
13
Q
Are compounds that contain delocalised electrons more or less stable than those that don’t? (1 mark)
A
More stable.
14
Q
Does benzene undergo electrophilic substitution? (1 mark)
A
Yes
15
Q
What is the catalyst for the nitration of benzene? (1 mark)
A
Concentrated H2SO4
16
Q
What reagents are in the nitrating mixture used to nitrate benzene? (2 marks)
A
Concentrated HNO3
Concentrated H2SO4
17
Q
What temperature should the nitration of benzene take place at? (1 mark)
A
50 degrees
18
Q
What happens if the temperature goes above 50 degrees when nitrating benzene? (1 mark)
A
Further substitutions take place, to produce dinitrobenzene.
19
Q
(if have paper)
Draw the mechanism of the nitration of benzene. (5 marks)
A
- Equation(s) to show the production of nitrite ion.
- Curly arrow from ring to nitrite ion.
- Arrow from bond that links hydrogen to ring in intermediate.
- The ring doesn’t go past carbons 2 and 6 in intermediate.
- Correct products and regeneration of sulfuric acid.
20
Q
What do halogens need to react with benzene? (1 mark)
A
A catalyst called a halogen carrier.
21
Q
What are the reagents and conditions for the bromination of benzene? (2 marks)
A
RTP
React with AlBr3 or FeBr3
22
Q
What are the products of the bromination of benzene? (1 mark)
A
Bromobenzene
Hydrogen bromide
23
Q
(if have paper)
Draw the mechanism of the chlorination of benzene. (5 marks)
A
- Equation(s) to show the production of chlorine ion (with 1+ charge).
- Curly arrow from ring to chlorine ion.
- Arrow from bond that links hydrogen to ring in intermediate.
- The ring doesn’t go past carbons 2 and 6 in intermediate.
- Correct products and regeneration of FeCl3/AlCl3.
24
Q
What is alkylation? (1 mark)
A
The addition of an alkyl group (contains C and H, with single C bonds).
25
What does benzene react with to produce an alkylbenzene? (1 mark)
A haloalkane.
26
What is the catalyst used in the alkylation of benzene? (1 mark)
AlCl3
27
(if have paper)
Draw the mechanism to produce ethylbenzene. (5 marks)
1. Equation(s) to show the production of electrophile ion (with 1+ charge), from chloroethane and AlCl3.
2. Curly arrow from ring to electrophile.
3. Arrow from bond that links hydrogen to ring in intermediate.
4. The ring doesn't go past carbons 2 and 6 in intermediate.
5. Correct products and regeneration of AlCl3.
28
What is acylation? (1 mark)
The addition of an acyl group (R-C=O).
29
What does benzene react with to produce an aromatic ketone? (1 mark)
Acylchloride
30
What is the catalyst used in the acylation of benzene? (1 mark)
AlCl3
31
(if have paper)
Draw the mechanism to produce phenylpropanone. (5 marks)
1. Equation(s) to show the production of electrophile ion (with 1+ charge), from propanoylchloride and AlCl3.
2. Curly arrow from ring to electrophile.
3. Arrow from bond that links hydrogen to ring in intermediate.
4. The ring doesn't go past carbons 2 and 6 in intermediate.
5. Correct products and regeneration of AlCl3.
32
Why does benzene need a halogen carrier catalyst to react with bromine, but an alkene doesn't? (3 marks)
Benzene has delocalised electrons spread above and below the plane.
This means the electron density around any 2 carbons in a benzene ring is less than a C=C bond in an alkene.
So when a non-polar molecule, like bromine, approaches benzene there is insufficient pi-electron density to polarise the molecule.
33
What are the reagents and conditions of the alkylation of benzene? (2 marks)
Haloalkane
AlCl3
Reflux
34
What are the reagents and conditions of the acylation of benzene? (3 marks)
Acylchloride
Anhydrous conditions
AlCl3
Reflux
35
How does an alkene decolourise bromine water?
By electrophilic addition.
36
What is a phenol? (1 mark)
An organic compound that contains a hydroxyl group bonded to an aromatic ring.
37
Why are phenols less soluble in water than alcohols? (1 mark)
Because of the presence of the non-polar benzene ring.
38
What do phenols partially dissociate into in water? (1 mark)
A phenoxide ion and a proton.
39
Do phenols react with sodium hydroxide? (1 mark)
Yes
40
What is produced when phenol and sodium hydroxide react? (2 marks)
Sodium phenoxide
Water
41
Draw sodium phenoxide. (1 mark)
Look it up
42
What is produced when phenol and bromine react? (2 marks)
2, 4, 6- tribromophenol
3HBr
43
What two products can be produced when phenol reacts with nitric acid? (2 marks)
2-nitrophenol
or
4-nitrophenol
44
What are the reagents and conditions for the nitration of phenol? (1 mark)
Dilute nitric acid
RTP
45
What are the reagents and conditions for the bromination of phenol? (1 mark)
Bromine water
RTP
46
Why is phenol more reactive than benzene? (4 marks)
The O in the OH groups contributes another lone pair of electrons
to the pi-system of phenol,
this increases the electron density of the molecule,
making it more susceptible to electrophilic attack.
47
What is observed when phenol reacts with bromine water? (1 mark)
A white precipitate is formed.
48
What is an activating group, in aromatic chemistry, and how do they work? (4 marks)
Is electron donating,
and makes the aromatic ring more susceptible to electrophilic attack,
by increasing the electron density in the benzene ring
at positions 2, 4, and 6.
49
What is a deactivating group? (5 marks)
ls electron withdrawing
and makes the aromatic ring less susceptible to electrophilic attack,
by decreasing the electron density at positions 2, 4, and 6.
This means electrophiles are more likely to bond at carbons 3 and 5.
50
Why are deactivating groups 3-5 directing? (3 marks)
They withdraw electron density form the benzene ring,
decreasing electron density at positions 2, 4, and 6,
therefore electrophiles **relatively** more likely to bond to positions 3 and 5.
51
Why does chlorine react more readily with a C6H5N(CH3)2 than benzene? (3 marks)
Lone pair on nitrogen becomes partly dissociated into the pi bond system in benzene ring.
This causes the electron density to increase.
The benzene ring in the molecule has a greater ability to polarise the Cl-Cl bond.
52
What is an aldehyde? (1 mark)
The C=O group is at the end pf a carbon chain.
53
What is a ketone? (1 mark)
The C=O group is joined to two carbon atoms in the carbon chain.
54
How is the aldehyde group written in a structural formula? (1 mark)
CHO
55
How is the ketone group written in a structural formula? (1 mark)
CO
56
What is the ending (naming) for an aldehyde? (1 mark)
al
57
What is the ending (naming) for a ketone? (1 mark)
one
58
What aldehyde does the crested auklet bird release during breeding season? (1 mark)
Octanal
59
Do aldehydes undergo oxidation? (1 mark)
Yes
60
Do ketones undergo oxidation? (1 mark)
No
61
What are the reagents and conditions for the oxidation of an aldehyde? (2 marks)
Reflux
Potassium dichromate and sulfuric acid or acidified potassium dichromate
62
What is the product of an aldehyde being oxidised? (1 mark)
Carboxylic acid
63
Do aldehydes and ketones react with nucleophiles, why/why not? (2 marks)
Yes
The C=O bond is polar
64
What reduces aldehydes and ketones? (1 mark)
NaBH4 and water
65
What is a carbonyl compound? (1 mark)
A compound which contains a C=O functional group- aldehydes and ketones.
66
What are aldehydes reduced to? (1 mark)
Primary alcohols
67
What are ketones reduced to? (1 mark)
Secondary alcohols
68
Draw the mechanism of the reaction of propanone with NaBH4 and water. (5 marks)
1. Curly arrow from C=O bond to delta negative oxygen.
2. Curly arrow from hydride ion (H-) to delta positive carbon.
3. Curly arrow from negative oxygen to delta positive hydrogen in water in intermediate.
4. Curly arrow from H-O bond to delta negative oxygen in water.
5. Correct products, propan-2-ol and OH- ion.
69
What does the reaction of a carbonyl compound with hydrogen cyanide produce? (1 mark)
A hydroxynitrile
70
Draw the mechanism of the reaction of propanal with hydrogen cyanide. (4 marks)
1. Curly arrow from C=O bond to delta negative oxygen.
2. Curly arrow from cyanide ion (-CN) to delta positive carbon.
3. Curly arrow from negative oxygen to positive hydrogen ion.
4. Correct product, 2-hydroxybutanenitrile.
71
What is a nucleophile? (1 mark)
An electron pair donor.
72
What does 2,4-DNP short for? (2 marks)
2,4- dinitrophenylhydrazine
73
What is 2,4-DNP used for? (1 mark)
To detect the presence of the carbonyl functional groups.
74
What is a positive result for a carbonyl group, using 2,4,-DNP? (1 mark)
Orange precipitate is formed.
75
Describe the test for aldehydes/ketones. (2 marks)
Add 2,4-DNP and a few drops of sulfuric acid/methanol.
Positive result: orange precipitate formed.
76
What is Tollen's reagent used for? (1 mark)
To test for an aldehyde.
77
What is the result an aldehyde gives for Tollen's test? (1 mark)
Positive- silver mirror
78
How is Tollen's reagent prepared? (3 marks)
Add sodium hydroxide to silver nitrate
until a brown precipitate forms.
Add dilute ammonia until the precipitate dissolves.
79
How can the result of the test for carbonyl compounds (2,4DNP) be used to identify the carbonyl compound? (2 marks)
Each precipitate produced has a different melting point,
this can be compared to the known melting points of the derivatives.
80
Are carboxylic acids soluble in water, why/why not? (2 marks)
Yes, because the C=O is polar.
81
Explain the trend in solubility of carboxylic acids. (2 marks)
As number of carbon sin chain increase, solubility decreases
because the non-polar chain has more of an effect on the overall polarity of the molecule.
82
What are dicarboxylic acids? (1 mark)
Carboxylic acids that contain two carboxyl groups.
83
What is the ending (name) of a dicarboxylic acid? (1 mark)
'anedioic acid'
84
What is the ion formed from a carboxylic acid called? (1 mark)
carboxylate ion
85
Are the boiling points of carboxylic acids higher or lower than similar Mr alcohols? (1 mark)
Higher
86
Why are the boiling points of carboxylic acids higher than similar Mr alcohols? (3 marks)
Carboxylic acids can form 2 hydrogen bonds between molecules,
whereas alcohols can only form 1 hydrogen bond between molecules.
So more energy is required to overcome these forces.
87
Why are carboxylic acids acidic? (2 marks)
The acidic nature of carboxylic acids is due to the relatively high stability of the carboxylate anion which forms from the delocalisation of the negative charge.
88
Fill in the gap:
The more charge can be spread around, the more ___________ an ion becomes.
The more charge can be spread around, the more stable an ion becomes.
89
Why are alcohols not acidic? (2 marks)
They are very poor at losing H+ ions,
due to there being no way of delocalising the negative charge of the negative ion formed if an alcohol lost an H+ ion.
90
metal + carboxylic acid -->
(2 marks)
H2 and carboxylate salt
91
metal oxide + carboxylic acid -->
(2 marks)
water + carboxylate salt
92
alkali + carboxylic acid -->
(2 marks)
water + carboxylate salt
93
carbonate + carboxylic acid -->
(2 marks)
CO2 + water + carboxylate salt
94
What is the functional group of an ester? (1 mark)
COO
95
What is the functional group of an acyl chloride? (1 mark)
COCl
96
What is the structural formula of ethanoic anydride? (2 marks)
(CH3CO)2O
97
What is esterfication? (2 marks)
When alcohol and a carboxylic acid react to produce an ester and water.
98
What is produced when an acyl chloride and alcohol react? (2 marks)
An ester and HCl
99
What is produced when an acid anhydride and alcohol react? (2 marks)
An ester and a carboxylic acid.
100
What is produced when an acyl chloride and phenol react? (2 marks)
A phenyl ester and HCl
101
How are acid anhydrides formed? (2 marks)
Condensation reaction
between 2 carboxylic acid molecules.
102
What are the reagents and conditions for esterification? (2 marks)
alcohol is warmed
sulfuric acid catalyst
103
Esters can be hydrolysed by an aqueous _____ or a ______.
(1 mark)
Acid or a base
104
____________ hydrolysis is the opposite of esterification.
(1 mark)
Acid hydrolysis is the opposite of esterification.
105
What are the reagents and conditions for the acid hydrolysis of an ester? (2 marks)
reflux
dilute **aqueous** acid
106
What is the equation or the acid hydrolysis of an ester? (3 marks)
ester + water --> carboxylic acid + alcohol
107
Is acid hydrolysis reversible? (1 mark)
yes
108
Is alkaline hydrolysis reversible? (1 mark)
no
109
What are the reagents and conditions for the alkaline hydrolysis of an ester? (2 marks)
reflux
**aqueous** alkali
110
What is the equation or the alkaline hydrolysis of an ester? (3 marks)
ester + OH- --> carboxylate ion + alcohol
111
What is the chemical formula of thionyl chloride? (1 mark)
SOCl2
112
Describe how an acyl chloride is prepared. (3 marks)
Carboxylic acid is reacted with thionyl chloride
to produce an acyl chloride, sulfur dioxide, and hydrochloric acid.
Fractional distillation is used to separate the acyl chloride from any excess acid or thionyl chloride.
113
Once a carboxylic acid has reacted with thionyl chloride, how is the acyl chloride separated from the other products? (1 mark)
Fractional distillation
114
What is produced when an acyl chloride and water react? (2 marks)
Carboxylic acid and HCl
115
Why must acylation reactions of acyl chlorides be carried out in anhydrous conditions? (2 marks)
Acyl chlorides react vigorously with water
releasing HCl fumes, which are corrosive/toxic.
116
What is produced when an acyl chloride reacts with ammonia? (2 marks)
Primary amide
Ammonium chloride
117
What is produced when an acyl chloride reacts with an amine? (2 marks)
Secondary amide
An ammonium chloride compound
118
What two things can react with acyl chloride to produce an amide? (2 marks)
Ammonia
An amine
119
What is produced when an acid anhydride reacts with a phenol? (2 marks)
A phenyl ester and carboxylic acid
120
Draw the mechanism of the reaction between ethanoyl chloride and methylamine. (8 marks)
Step 1:
1. Curly arrow from lone pair on methylamine to carbon in ethanoyl chloride
2. Curly arrow from double bond to oxygen o oxygen
Step 2:
3. Correct intermediate with positive N
4. Curly arrow from bond to chlorine to chlorine
5. Curly arrow from negative oxygen to bond, reforming the double bond
Step 3:
6. Curly arrow from hydrogen on N to N
7. Curly arrow from a second methylamine molecule to hydrogen ion
Step 4:
8. Correct products:
CH3CONHCH3 and CH3NH3+ Cl-
121
Describe how ethyl propanoate is prepared. (4 marks)
1. Add ethanol and propanoic acid to boiling tube
2. Add few drops of concentrated sulfuric acid
3. Heat under reflux
4. Add sodium carbonate solution
122
What are the reagents and conditions for an alcohol and an acid anhydride to react? (2 marks)
Heated under reflux
Anhydrous conditions
123
What are the reagents and conditions for an alcohol an acyl chloride to react? (2 marks)
RTP
anhydrous conditions
124
What is used to purify an ester after it has been produced, how does it purify it? (2 marks)
Calcium carbonate, removes traces of alcohol.
125
What is the function of sodium carbonate solution in the preparation of an ester? (2 marks)
It reacts with the traces of sulfuric acid and alcohol, neutralising them to produce water and soluble salts.
126
What is optical isomerism? (1 mark)
When the mirror images of molecules are non-superimposable.
127
What is a chiral carbon atom? (1 mark)
A carbon atom that has four different groups attached to it.
128
What are two compounds that are optical isomers of each other called? (1 mark)
Enantiomers
129
What is a 50/50 mixture of two enantiomers called? (1 mark)
A racemic mixture/ racemate
130
What is the main difference between optical isomers? (1 mark)
They affect plane polarised light differently.
131
Why does a racemate have no effect on the plane of light? (1 mark)
Each enantiomer rotates the plane polarised light by the same amount, but in the opposite direction.
This means the effects of the enantiomers cancel out.
132
What is the functional group of an amine? (1 mark)
NH2
133
What are amines derived from? (1 mark)
Ammonia
134
What are the two types of amines? (2 marks)
Aliphatic amine
Aromatic amine
135
What is an aliphatic amine? (1 mark)
The nitrogen atom is attached to at least one carbon chain.
136
What is an aromatic amine? (1 mark)
The nitrogen atom is attached to an aromatic ring.
137
What is a primary amine? (1 mark)
The nitrogen is attached to one a carbon chain.
138
What is a secondary amine? (2 marks)
The nitrogen is attached to 2 carbon chains.
139
What is the tertiary amine? (3 marks)
The nitrogen is attached to 3 carbon chains.
140
How do you name secondary/tertiary amines? (2 marks)
Call it an N-substituted derivative of the larger group.
141
What is serotonin? (2 marks)
An amine that acts as a neurotransmitter, controlling sleep, appetite, memory and many other things.
142
What is pseudoephedrin? (2 marks)
An amine that is used in decongestion medications.
143
Why do amines act as bases in chemical reactions? (1 mark)
They have a lone pair of electrons on the N that can accept a proton.
144
What is the name of an amine ion? (1 mark)
ammonium ion
145
How do amines react with acids? (1 mark)
Amines neutralise amines to make salts.
146
How do you prepare a primary aliphatic amine, using a haloalkane? (3 marks)
Ammonia + haloalkane--> Ammonium salt
Ammonium salt + alkali (aq) --> amine
147
What are the conditions required to prepare an aliphatic amine from a haloalkane, and explain why they are used? (4 marks)
ethanol- prevents substitution of haloalkane by water to produce alcohols
excess ammonia- reduces further substitution
148
How do you prepare a secondary/tertiary amine, using a haloalkane? (2 marks)
Prepare a primary amine
Primary amine + haloalkane --> ammonium salt
ammonium salt + alkali (aq) --> amine
149
How do you prepare an aromatic amine? (3 marks)
Reduction of nitrobenzene- heated under reflux with tin and HCl
Add excess NaOH
150
What functional groups do amino acids contain? (2 marks)
NH2
COOH
151
How do amino acids react with acids? (2 marks)
The amine group is basic, and react with acids to make salts.
152
How do amino acids react with aqueous alkalis? (2 marks)
The carboxylic acid group reacts with the alkali to form a salt.
153
How do amino acids react with alcohols? (2 marks)
The carboxylic acid group reacts with the alcohol to form an ester.
154
What are the conditions required to form an ester from an amino acid? (2 marks)
heating
alcohol
concentrated sulfuric acid
155
What are amides the products of? (2 marks)
acyl chloride + ammonia/amines
156
What is the functional group of an amide? (2 marks)
Carbonyl group bonded to a nitrogen.
CON or CONH or CONH2
157
What is a primary amide? (1 mark)
The nitrogen is attached to one a carbon chain.
158
What is a secondary amide? (1 mark)
The nitrogen is attached to two carbon chains.
159
What is a tertiary amide? (1 mark)
The nitrogen is attached to three carbon chains.
160
Do amines have hydrogen bonds between molecules, why/why not? (2 marks)
Yes, they contain N-H bonds.
161
Explain why a tertiary amine has a much lower boiling point than primary and secondary amines of similar Mr. (2 marks)
They have no hydrogen atoms directly attached to the nitrogen, so hydrogen bonding cannot happen between molecules.
162
What is trend in solubility of amines as their caron chains get longer, why? (2 marks)
Less soluble as carbon chains increase in length,
because they force their way between water molecules, breaking the hydrogen bonds between water molecules and nitrogens in amines.
163
Draw the mechanism of the production of an amine from a haloalkane. (6 marks)
Step 1:
1. Curly arrow from ammonia to carbon bonded to halogen in haloalkane
2. Curly arrow from bond C-halogen bond to halogen
Step 2:
3. Ammonia is now bonded to carbon chain from haloalkane in intermediate
4. Curly arrow from N-H bond to N+
5. Curly arrow from released another ammonia molecule to hydrogen
6. Correct product
164
Describe how an amine is produced by the reduction of a nitrile compound, in a lab, include the reagents and conditions. (4 marks)
1. haloalkane + KCN --> nitrile compound
2. nitrile compound + 4[H] --> amine
LiAlH4 in ethoxyethane
165
Describe how an amine is produced by the reduction of a nitrile compound, in industry, include the reagents and conditions. (4 marks)
1. haloalkane + KCN --> nitrile compound
2. nitrile compound + 2H2 --> amine
Ni catalyst + heat
166
Why is phenylamine a weaker base than ammonia? (2 marks)
The lone pair of electrons on the nitrogen of the phenylamine is delocalised into the benzene ring,
making it less available to combine with hydrogen ions.
167
What zwitterton does an amino acid exist as at a low pH? (1 mark)
The NH2 group is protonated to NH3+
168
What zwitterton does an amino acid exist as at a neutral pH? (2 marks)
The NH2 group is protonated to NH3+
The COOH group is unprotonated to COO-
169
What zwitterton does an amino acid exist as at a high pH? (1 mark)
The COOH group is unprotonated to COO-
170
What is condensation polymerisation? (1 mark)
The joining of monomers with the loss of a small molecule (usually H20/HCl)
171
What links the monomers in polyesters? (1 mark)
Ester linkages
172
What functional groups must a monomer contain to turn a polyester by condensation polymerisation? (2 marks)
COOH and OH
173
A polyester is made of two monomers, what functional groups must each monomer contain? (2 marks)
One contains 2 COOH groups
One contains 2 OH groups
174
What is lactic acid derived from? (1 mark)
Maize
175
Give an example of a polyester formed from one monomer. (1 mark)
Poly (lactic acid)
Poly (glycolic acid)
176
Give an example of a polyester formed from two monomers. (1 mark)
Treylene (PET)
177
What links the monomers in polyamides? (1 mark)
Amide linkages
178
What functional groups must a monomer contain to turn a polyamide by condensation polymerisation? (2 marks)
COOH/COCl and NH2
179
A polyamide is made of two monomers, what functional groups must each monomer contain? (2 marks)
One contains 2 COOH/COCl groups
One contains 2 NH2 groups
180
What type of polymer do amino acids form, why? (2 marks)
Polyamide
Contain a COOH and a NH2
181
How are condensation polymers hydrolysed? (1 mark)
Using an **aqueous, hot** acid/alkali
182
What is formed when a polyester undergoes acid hydrolysis? (2 marks)
Alcohol
Carboxylic acid
183
What is formed when a polyester undergoes alkali hydrolysis? (2 marks)
Alcohol
A carboxylic salt
184
What is formed when a polyamide undergoes acid hydrolysis? (2 marks)
Carboxylic acid
Ammonium ion
185
What is formed when a polyamide undergoes alkali hydrolysis? (2 marks)
Amine
A carboxylic salt
186
Why are condensation polymers biodegradable? (2 marks)
Because contain C-O or C-N polar bonds in the main chain, which are susceptible to chemical attack.
187
What are the strongest forces between polymer chains in addition polymers? (1 mark)
Induced dipole-dipole interactions
188
What are the strongest forces between polymer chains in polyesters? (1 mark)
Permanent dipole-dipole interactions
189
What are the strongest forces between polymer chains in polyamides? (1 mark)
Hydrogen bonds
190
Haloalkane + NaCN -->
Nitrile + X-
191
Haloalkane + NaCN -->
Nitrile + X-
192
Aldehyde + HCN -->
Nitrile + OH-
193
Ketone + HCN -->
Nitrile + OH-
194
What does the reduction of a nitrile make?
Amine
195
What does the hydrolysis of a nitrile make?
Carboxylic acid
196
What is used in the reduction of nitriles?
H2 + Ni catalyst
197
What is used in the hydrolysis of nitriles?
Heating with dilute (aq) acid
198
How do you prepare a solid from a liquid reaction mixture? (4 marks)
- Set up Buchner pressure apparatus
- Put filter paper inside the funnel, and wet with solvent
- Pour reaction mixture into funnel
- Rinse beaker and add too
- Leave under suction for a few minutes to dry
199
Describe how you would recrystallise an impure solid to increase purity? (3 marks)
- Dissolve the impure sample in a minimum volume of warm solvent
- Allow solution to cool to room temperature, then place in a water bath until crystals reform
- Filter using Buchner apparatus
200
How do you evaluate the purity of the sample from its melting point range?
Pure samples have a very small melting range.
201
How do you determine the melting point range of a sample? (3 marks)
- Seal the end of a capillary tube using a Bunsen burner
- Fill with crystals to about 3mm depth
- Use electrically heated melting point apparatus to take its melting point
202
What are two benefits of using reflux?
Speeds up the reaction.
Prevents reagents being lost.
203
What method should be used to separate soluble and insoluble products?
-Add mixture to separating funnel
- Add water, shake
- Let settle
- If could contain trace amounts of acid, add NaHCO3
- Run off lower layer
- Add anhydrous CaCl2 to organic layer (drying agent)
204
What is gas chromatography (GC) used for?
To separate volatile liquids.
205
What happens in gas chromatography (GC)?
- A small amount of the volatile mixture is injected into the apparatus
- The mobile carrier gas carries the components through the column (inside a thermostatically controlled oven) where it separates into different liquids
- Slower it moves--> greater affinity with stationary phase
- Produces a chromatagram
206
What is the mobile phase of GC?
An inert gas (e.g. nitrogen)
207
Wat is the stationary phase of GC?
Solid/ high boiling point liquid coated on a solid support
208
What do the number of peaks on a GC chromatogram represent?
The number of substances in the mixture.
209
What does the area under each peak represent on a GC chromatogram?
The relative amount of the substance in the mixture
210
What is the test for an alkene?
Add bromine water
Orange --> colourless
211
What is the test for the halogens?
Add silver nitrate and ethanol at 50 degrees
Chloro- white
Bromo- Cream
Iodo- Yellow
212
What is the test for a carbonyl group?
Add 2,4-DNP
Orange precipitate
213
What is the test for an aldehyde group?
Add Tollens reagent + warm
Silver mirror
214
What is the test for a primary/secondary alcohol?
Add K2Cr2O7 + warm
Orange --> Green
215
What is the test for a carboxylic acid?
Add NaCO3 (aq)
Fizzing
216
What is the test for a phenol?
Bromine water
White precipitate
217
What is resonance?
When the nucleus can absorb energy and rapidly flip between the two spin states.
218
What is used in a NMR spectrometer?
A super-conducting electromagnet, cooled by liquid helium.
219
What is chemical shift in NMR?
When the electrons in atoms shift the energy and radio frequency needed for NMR.
220
What is the unit for chemical shift?
ppm
221
What substance is used as a standard reference in NMR?
TMS- has a chemical shift of 0ppm
222
What happens when deuterium oxide is added to a H NMR spectrum reading, and why?
Any O-H or N-H peaks disappear, because the hydrogen gets replaced by a D, meaning it isn't detected.
223
What do the areas under a proton NMR spectra tell us?
The relative number of each type of proton.
224
What is the splitting rule in proton NMR?
For a proton with n protons attached to an adjacent carbon atom, the number of sub-peaks in a splitting pattern is n+1.
225
What is the chemical environment of a carbon determined by?
The position of the atom within the molecule and symmetry.
