Organic Flashcards
(387 cards)
1
Q
What is the empirical formula?
A
The simplest whole number ratio of atoms of each element in a compound
2
Q
What is molecular formula?
A
The true number of atoms of each element in a compound
3
Q
What is the general formula?
A
All members of a homologous organic series follow the general formula
4
Q
What is the structural formula?
A
Shows the structural arrangement of atoms within a molecule
5
Q
What is the displayed formula?
A
Shows every atom and every bond in an organic compound
6
Q
What is the skeletal formula?
A
Shows only the bonds in a compound and any non-carbon atoms (hydrogen is assumed to be bonded to carbon unless otherwise stated)
7
Q
What is a homologous series?
A
Series of organic compounds which contain the same functional group
8
Q
What do reaction mechanisms show?
A
The movement of electrons within a reaction
9
Q
What are isomers?
A
Molecules with the same molecular formula but with a different arrangement of atoms within the molecule
10
Q
What are structural isomers?
A
Have the same molecular form but different structural arrangement of the atoms, the chain of carbon can be straight or have branches
11
Q
What are positional isomers?
A
Same molecular formula and functional group but the functional group is in a different position on the carbon chain
12
Q
What are functional group isomers?
A
Same molecular formula but have different functional groups
13
Q
What are stereoisomers?
A
Same molecular formula but different spatial arrangement
14
Q
What type of isomerism is E-Z?
A
stereoisomerism
15
Q
Why does E-Z isomerism arise?
A
Limited rotation around the carbon-carbon double bond
16
Q
What is the E isomer in E-Z isomerism?
A
groups are apart
17
Q
What is the Z isomer in E-Z isomerism?
A
groups are together
18
Q
What is the Cahn-Inglod-Prelog (CIP) priority rules when it comes to E-Z isomerism?
A
Higher priority is given to the adjacent atom with the highest Ar and if they’re the same keep going down the chain till atom with higher Ar is reached
19
Q
What is an ether functional group?
A
C-O-C
20
Q
What is the general formula of alkanes?
A
Cn H2n+2
21
Q
Are alkanes saturated or unsaturated?
A
Saturated hydrocarbons (only contain single bonds)
22
Q
What is petroleum (crude oil)?
A
A mixture consisting mainly of alkane hydrocarbons
23
Q
How can petroleum (crude oil) be separated?
A
Fractional distilliation
24
Q
Why do different chain length alkanes have different boiling points?
A
The higher the Mr the greater the VDW and the higher the boiling point so the longer the carbon chain the higher the boiling point
25
How does fractional distillation of petroleum (crude oil) work?
The mixture is heated and vaporised and then fed into a fractionating column
The vapour rises and as it does it cools and condenses
It is then separated into its different fractions which can then be pumped away for their different uses
26
What is collected at the top of a crude oil fractionating column?
Short carbon chains
27
What is the order of crude oil fractions from top to bottom?
Refinery gases
Gasoline (petrol)
Naphtha
Kerosene
Diesel (gas oil)
Lubricating oil (mineral oil)
Fuel oil
Bitumen
28
How are refinery gases used?
Camping gas
29
How is gasoline used?
Petrol in cars
30
How is kerosene used?
jet fuel
31
How is diesel used?
Diesel fuel, central heating
32
How is fuel oil used?
Ships, power stations
33
How is Bitumen used?
Road surfacing
34
How is naphtha used?
Processed to make petrochemicals
35
What length of alkane carbon chains are more in demand?
Smaller chain alkanes
36
What type of reaction is cracking?
Decomposition
37
What is cracking?
The breaking down of longer carbon chain molecules into smaller more useful molecules
(breaking C-C bonds)
38
What are the two types of cracking?
Thermal and Catalytic
39
What does thermal cracking produce?
alkanes and alkenes
40
What does catalytic cracking produce?
Aromatic compounds and motor fuels
41
What are the conditions used in thermal cracking?
High temp - 1000°C
High pressure - 70 atm
42
What are the conditions used in catalytic cracking?
Zeolite catalyst
High temp - 450°C
Slight pressure
43
Why does using a zeolite catalyst in catalytic cracking cut costs?
Means the reaction can be done at low pressure and a lower temperature (also speeds up reaction)
44
Why do alkanes make good fuels?
Release a lot of energy when burned
45
What do we do with fuels?
Combust them
46
What are the products of complete combustion of alkanes?
CO2 and H2O
47
What are the products of incomplete combustion of alkanes?
CO and H2O
48
What are the products of incomplete combustion alkanes (when there's even less O2)?
C(s) and H2O
49
What is the downside to burning alkanes?
Produces lots of pollutants
50
Whats the problem with carbon monoxide?
Poisonous as as it binds to the same sites on haemoglobin molecules as oxygen does so prevents oxygen being carried around the body
51
How is carbon monoxide removed from exhaust gases?
Using a catalytic converter
52
Whats the problem with burning fossil fuels?
Produces CO2 which is a greenhouse gas
(also non-renewable)
53
Whats the problem with greenhouse gases?
Really good at absorbing infrared radiation which means it isn't all reflected as it ought to be which leads to the greenhouse effect and global warming
54
How are oxides of nitrogen produced in a car engine?
The high pressure and temperature causes the nitrogen and oxygen in the air to react together
55
What are carbon particulates?
Small fragments of unburned hydrocarbon that can cause serious respiratory problems
56
What is the problem when hydrocarbons and nitrogen oxides react in the presence of sunlight?
Forms ground-level ozone
57
Whats the problem with ground-level ozone?
Major component of smog, irritates peoples eyes and aggravates respiratory problems
58
What is the process of removing sulphur dioxide called?
Flue - gas desulphurisation
59
Whats the problem with SO2?
Acid rain which ruins habitats, destroys trees and vegetation, kills fish in lakes, corrodes buildings
60
What catalyst is used in a catalytic converter?
Rhodium (or platinum)
61
What does the combustion of hydrocarbons containing sulfur lead to?
sulfur dioxide
62
What are the there steps of free-radical substitution?
Initiation
Propagation
Termination
63
What is produced in free radical substitutions?
Haloalkanes from alkanes and halogens
64
What is required for free radical substitution?
UV light
65
What is the initiation step of free radical substitution?
The break down of the halogen eg
Cl2 ---> 2Cl* UV light
66
What is the propagation step? (Cl* and CH4 as example)
Hydrogen is replaced and the Cl* is reformed as a catalyst
Cl* + CH4 ---> *CH3 + HCl
*CH3 + Cl2 ---> CH3Cl + Cl*
67
What is the termination step in free radical substitution?
Two radicals join to end the chain reaction and form a stable product
eg *CH3 + *CH3 ---> C2H6
68
What is the problem with CFC's?
UV light from the sun causes CFC's to break creating free radicals which then react with ozone in the atmosphere and deplete it
69
Which bond is stronger C-F or C-Cl?
C-F greater electronegative difference
70
Show how a chlorine radical depletes ozone?
Cl* + O3 ---> O2 + ClO*
ClO* + O3 ---> 2O2 + Cl*
71
What does the ozone layer do?
Protects us from UV radiation which can damage the skin and cause cancer (absorbs it)
72
Why were CFC's banned?
As a result of research by different groups in the scientific community how provided evidence for legislation to ban the use of CFC's as solvent and refrigerants
73
What do we now use instead of CFC's?
Chemists have developed alternative chlorine free compounds
74
Why do halegenoalkanes contain polar bonds?
Halogens are more electronegative than carbon atoms so electron density is drawn towards the halogen
75
What is a nucleophile?
Species that contains a lone electron pair that is attracted to δ+ regions of molecules
76
Examples of nucleophiles
: C(-) ≡ N
:NH3
:OH
77
What mechanism means you get an alcohol from a halogenolalkane?
nucleophilic substitution
78
What mechanism means you get an amine from a halogenoalkane?
nucleophilic substitution
79
How does the carbon-halogen bond enthalpy influence the rate of reaction?
The greater the Mr of the halogen, the lower the bond enthalpy meaning it is broken more easily ∴ the rate is quicker
80
Why cant you have nucleophilic substitution with tertiary halogenoalkanes?
The nucleophile can only approach the carbon from the side with the halogen (as other side too crowded) but the halogen has a δ- charge so repels the nucleophile
81
What happens in nucleophilic substitution?
The nucleophile attacks the δ+ carbon bonded to the halogen (approached from opposite side to halogen) and then the carbon-halogen shared pair of electron are both given to the halogen to produce a halide
82
What is the role of the nucleophile in a nucleophilic substitution?
electron donor
83
What are the conditions needed for elimination?
High temperature
Ethanol (alcoholic) solvent
heat under reflux
84
What is the role of the nucleophile in elimination?
Proton acceptor (acts as a base)
85
How do you produce an alkene from a halogenoalkane?
elimination
86
What happens in an elimination mechanism?
Nucleophile attacks a hydrogen on the adjacent carbon to the halogen
That hydrogen-carbon bond then gives its electrons to the carbon-carbon bond (when nucleophile is :OH this makes a water molecule)
Then the electrons in the carbon-halogen bond gives both electrons to the halogen to make a halide
(like a waterfall affect)
87
Why does the proportion of water to ethanol matter when you have nucleophiles and halogenoalkanes?
water encourages substitution
ethanol encourages elimination
88
How do you favour nucleophilic substitution over elimination?
lower temp.
more dilute solutions
more water in the solvent mixture
89
How do you favour elimination over nucleophilic substitution?
higher temp.
conc. solutions
pure ethanol as solvent
90
What type of halogenoalkanes undergo elimination by a nucleophile under the right conditions? (primary, secondary or tertiary)
secondary and tertiary
91
What are alkenes?
Unsaturated hydrocabons
92
Why are alkenes unsaturated?
Contain a double covalent bond
93
Why is a carbon-carbon double bond susceptible to an attack from electrophiles?
Area of high electron density
94
How can you test for alkenes?
Add it to bromine water, turns solution from orange to colourless
95
What type of isomerism is common in alkenes?
E-Z stereoisomerism (restricted rotation around C=C)
96
What is an electrophile?
Electron pair acceptor (attracted to areas of high electron density)
97
Examples of electrophiles
HBr
Br2
H2SO4
98
What mechanism reaction produces alcohols and halogenoalkanes from alkenes?
electrophilic addition
99
What is electrophilic addition?
Electrophile attacks carbon double bond and forms a carbocation (always forms the most stable)
Then the nucleophile which formed from the electrophile bond breaking attacks the positively charged carbocation
100
What is a carbocation?
Carbon atom with only 3 bonds (has a positive charge)
101
What is the major product in electrophilic addition?
The product formed via the most stable carbocation
102
What does a tertiary carbocation mean?
The three bonds on the carbocation are all carbon-carbon single bonds
103
Why are tertiary carbocations more stable than secondary and primary ones?
Has more alkyl groups so greater inductive effect as each alkyl group pushes electrons onto the carbocation so spreads electrons more evenly round the molecule making it more stable
104
How do alkenes react with cold conc. sulfuric acid and what is the product called?
electrophilic addition
alkyl hydrogen sulfates
105
What happens when you react alkyl hydrogen sulfates with water and what are the conditions?
Make alcohols (and H2SO4)
Warm the reaction mixture
106
What are addition polymers produced from?
Alkenes when the double bond is broken to form a repeating unit
107
What is an addition polymer?
Long chain molecule made from lots of monomers joined together
108
How do you name addition polymers?
Poly (alkene made from)
109
What polymer do you get in high temperature and pressure?
Branched chain polymers
110
What are the properties of branched chain polymers?
Weaker and more flexible (weak VDW)
111
What polymer do you get in low temperature and pressure?
Straight chain polymers
112
What are the properties of straight chain polymers?
Strong and rigid (strong VDW)
113
Why are polymers unreactive?
They're saturated and non-polar
114
Why aren't polymers biodegradable?
Very unreactive
115
How do you make a polymer more flexible?
Add plasticiser as it gets between the polymer chains and pushes them apart, reducing the intermolecular force strength which makes them easier to bend
116
Why do polymers make good plastics?
Unreactive, multiple strong non-polar bonds
117
What is a use of polythene?
Shopping bags
118
What does PVC stand for?
polychloroethene
119
What is PVC?
Waterproof polymer which has a long closely packed chain
120
What are the properties of PVC at room temperature?
hard and brittle
121
How is rigid PVC used?
Drainpipes, Window frames
122
How is plasticised PVC used?
Electrical cable insulation, flooring tiles and clothing (more flexible)
123
What are the two ways to make ethanol?
Fermentation
Hydration of ethene
124
What are the conditions of fermentation to produce alcohols?
Anaerobic (oxygen free)
yeast catalyst
temp. 30-40°C
125
What is the equation for fermentation to make alcohol?
C6 H12 O6 ---> 2 C2 H5 OH + 2CO2
(yeast catalyst)
126
What are the advantages of fermentation to produce ethanol?
sugars renewable
cheap equipment
127
What are the disadvantages of fermentation to produce ethanol?
Batch process (its not continuous)
Ethanol needs distilling
128
What are the conditions needed for the hydration of ethene to make ethanol?
conc. acid (H3PO4 or H2SO4) catalyst
temp. 300°C
pressure 70 atm
(aqueous conditions)
129
What is the equation for the production of ethanol from the hydration of ethene?
C2H4 + H2O ⇌ C2H5OH
130
What are the advantages of ethanol production from the hydration of ethene?
Continuous process
Very high percentage yield (ethanol only product)
Produces purer product than fermentation
131
What are the disadvantages of ethanol production from the hydration of ethene?
ethene is non - renewable as comes from crude oil
132
What is ethanol used as?
biofuel
133
What is a biofuel?
fuel that's made from biological material that's recently died
134
What does carbon neutral mean?
no net release of CO2
135
Even if a reaction is carbon neutral why is the process not necessarily carbon neutral?
Transportation of reactants and products and machinery produce CO2
136
How is fermentation carbon neutral?
Glucose comes from photosynthesis:
6CO2 + 6H2O ---> C6H12O6 + 6O2
Glucose is fermented to form ethanol:
C6H12O6 ---> 2C2H5OH + 2CO2
Ethanol is combusted (used as a biofuel):
2C2H5OH + 6O2 ---> 4CO2 + 6H2O
∴ 6CO2 in and 6CO2 out
137
Why is yeast needed in fermentation to make ethanol?
Produces an enzyme which converts glucose to ethanol and carbon dioxide
138
Why is fermenation to produce ethanol done at 30-40°C?
optimum temperature for the enzymes
139
How is ethanol separated from the products of fermentation?
fractional distillation
140
What are the advantages of biofuel?
Renewable energy source
141
What are the disadvantages of biofuel?
Petrol car engines would need to be modified
Land would need to be used to grow crops for fuel meaning it cant be used to grow food
142
Why does fermentation to make ethanol have to be anaerobic?
Must be anaerobic for the yeast to work
143
How do you classify an alcohol as primary, secondary or tertiary?
How many alkyl groups are attached to the carbon that's bonded to the OH
144
What do you use to oxidise alcohols and whats the colour change?
acidified potassium dichromate ( K2 Cr2 O7 )
orange solution to green solution
145
What do primary alcohols oxidise to?
aldehydes
146
What do secondary alcohols oxidise to?
ketones
147
What do aldehydes oxidise to and what are the conditions?
carboxylic acid
heat under reflux
148
What do tertiary alcohols oxidise to?
they don't easily oxidise
149
What is the only way to oxidise tertiary alcohols?
burn them
150
What do ketones oxidise to?
aren't easily oxidised
151
What are the two tests to distinguish aldehydes and ketones?
Fehling's solution
Tollen's reagent
152
What do you observe when you add Fehling's solution to aldehydes and ketones?
aldehyde - blue solution to brick red ppt
Cu 2+ ---> Cu +
ketone - NVC
153
What do you observe when you add Tollen's reagent to aldehydes and ketones?
aldehyde - silver mirror forms
Ag+ ---> Ag
ketone - NVC
154
How do you get an aldehyde when oxidising a primary alcohol (eg ethanol)?
Distillation
Gently heat the alcohol with acidified potassium dichromate and use distillation apparatus as the aldehyde boils at a lower temp so is distilled off immediately
155
How do you get a carboxylic acid when oxidising a primary alcohol (eg ethanol)?
Reflux
The alcohol is heated under reflux with excess acidified potassium dichromate and vigorously oxidised. When aldehyde is produced it stays in the reaction mixture and is then oxidised to a carboxylic acid
156
Equation for the oxidation of a primary alcohol?
1° alcohol + [O] ---> aldehyde + H2O
aldehyde + [O] ---> carboxylic acid + H2O
157
Equation for the oxidation of a secondary alcohol?
2° alcohol + [O] ---> ketone + H2O
158
What type of mechanism means you get an alkene from an alcohol?
elimination
159
How are alkenes formed from the elimination of a water molecule from an alcohol used?
Addition polymers as they haven't had to come from crude oil
160
What catalyst is needed to form alkenes from the dehydration of alcohol?
conc. H2SO4
(conc. acid)
161
How do you test for alcohols?
Add acidified potassium dichromate
turns from orange solution to green
(not for 3° alcohols)
162
How do you test for aldehydes?
Add Tollen's reagent and silver mirror will form
163
How do you test for alkenes?
Add bromine water and shake
From orange solution to colourless
164
How do you test for carboxylic acids?
Add sodium carbonate which will produce CO2, collect this gas and bubble through limewater which will go cloudy if gas is CO2
165
What is High Resolution Mass Spectrometry?
More sensitive form of mass spectrometry which allows the Mr to be determined to several decimal places
166
How do you make Tollen's reagent? What is its formula
Silver nitrate and a few drops of sodium hydroxide and dilute ammonia solution
[Ag(NH3)2] +
167
How does Infrared spectroscopy work?
Beam of IR radiation is passed through a sample
Different covalent bonds absorb different frequencies of IR radiation so the varying amounts of absorption can be measured and recorded
168
What does the graph produced from IR spectroscopy show?
What frequencies of radiation the molecule is absorbing
169
How can a molecule be identified from its IR absorption graph?
Fingerprint region - each molecules is unique
170
How can an IR graph be used to find how pure a compound is?
Any impurities will produce extra peaks in the fingerprint region
171
What causes global warming?
Molecules of greenhouse gases (eg CO2, CH4, H2O vapour) absorb IR radiation from the sun and they re-emit some towards earth
So the higher the conc. of greenhouse gases the greater the greenhouse effect
172
What type of isomerism is optical isomerism?
stereoisomerism
173
Why does optical isomerism arise?
Chirality in molecules
174
What is a chiral centre?
A carbon with four different groups bonded around it so there is no line of symmetry to the molecule
175
What are enantiomers?
Two isomers that are mirror images of each other and cant be superimposed
176
What is plane polarised light?
Light that only vibrates in one direction
177
What affect do enantiomers have on plane polarised light?
One rotates it 90° clockwise and the other 90° anticlockwise
178
What is a racemic mixture?
Contains equal quantities of each enantiomer of an optically active compound
179
How do you know if a mixture is racemic?
Doesn't rotate plane polarised light
180
Why do you get optical isomers when nucleophilic addition happens to aldehydes and unsymmetrical ketones?
Nucleophiles are able to attack a molecule with a carbonyl group from above or below the C=O bond
181
How are chiral centres shown?
*
182
What is the functional group of aldehydes?
-CHO
183
What is the functional group of ketones?
RCOR'
184
What do aldehydes reduce to?
primary alcohols
185
What do ketones reduce to?
secondary alcohols
186
What is the reaction mechanism when aldehydes are reduced to primary alcohols?
nucleophilic addition
187
What is the reaction mechanism when ketones are reduced to secondary alcohols?
nucleophilic addition
188
What is the reducing agent used to reduce aldehydes and ketones to alcohols?
NaBH4 (sodium borohydride) dissolved in water with methanol
189
What is the overall equation for the reduction of aldehydes to primary alcohols?
RCHO + 2[H] ---> RCH2OH
190
What is the overall equation for the reduction of ketones to secondary alcohols?
RCOR' + 2[H] ---> RCH(OH)R'
191
Where do the H- ions and H+ ions used in the nucleophilic addition that reduces aldehydes and ketones to alcohols come from?
:H- nucleophile comes from the NaBH4
H+ comes from either the water or the methanol
192
What do you get when acidified KCN reacts with aldehydes and ketones?
hydroxynitriles
193
What type of reaction mechanism is the reaction between KCN and aldehydes and carbonates?
nucleophilic addition
194
What is a carbonyl compound?
Contains C=O
195
Why do you need acidified KCN instead of just KCN when reacting with aldehyde and ketones?
Need a source of H+ ions
196
Why is acidified KCN used instead of HCN in reactions?
HCN is hard to store as a gas and reacts to produce dangerous byproducts
197
What type of isomerism often occurs in hydroxynitriles?
optical isomerism
198
What are the dangers of using KCN?
Irritant
Extremely dangerous if ingested or inhaled
Can react with moisture to produce HCN which is a toxic gas
199
What must you do when handling KCN?
Wear gloves, safety goggles, lab coat and do any reactions in a fume cupboard
200
What is the overall equation between an aldehyde and KCN?
RCHO (aq) + KCN (aq) ---> RCH(OH)CN (aq) + K+ (aq)
(also with H+ (aq) )
product - hydroxynitrile
201
What is the overall equation between a ketone and KCN?
RCOR' (aq) + KCN (aq) ---> RC(OH)R'CN (aq) + K+ (aq)
(also with H+ (aq) )
product - hydroxynitrile
202
Why do aldehydes and ketones have higher boiling points than alkanes with a similar Mr?
All have similar VDW as similar no. electrons but it is due to permanent dipole attractions between carbonyl groups on the neighbouring molecules
203
Why do alcohols have a much higher boiling point than aldehydes and ketones with a similar Mr?
Aldehydes and ketones have permenant dipole attractions between carbonyl groups on neighbouring molecules but alcohols have hydrogen bonding between hyrdoxyl groups on neighbouring alcohol molecules
204
Why are the boiling points of ketones slightly higher than aldehydes?
Aldehydes have the carbonyl group at the end which gives a longer non-polar part of the molecule so it has less effective permanent dipoles than ketones
205
Why do branched chain aldehydes and ketones have a lower boiling point than straight chained ones?
Branching allows less interaction between molecules so less effective permanent dipole attractions
206
Rank from lowest to highest boiling points aldehydes, alcohols, alkanes, carboxylic acids (all have similar Mr)
Alkanes (VDW)
Aldehydes (permanent dipoles)
Alcohols (hydrogen bonding)
Carboxylic acids
207
How does solubility vary with carbon chain length of aldehydes and ketones?
Smaller chain lengths are more soluble
208
Why do short chain aldehydes and ketones mix well with water (are soluble)?
Polar carbonyl groups are able to from hydrogen bonds with water molecules
209
What is the functional group of carboxylic acids?
-COOH
210
What is the reaction between carboxylic acids and carbonates?
carboxylic acid + carbonates ---> salt + water + CO2
211
What is the functional group of esters?
-COO-
212
What is esterification?
Making esters by reacting carboxylic acids and alcohols
213
What are the conditions needed for esterification?
Strong acid catalyst (H2SO4)
Heated under reflux
214
What is the reaction between a carboxylic acid and an alcohol and whats it called?
Esterification or condensation
carbox. acid + alcohol ⇌ ester + water
(H+, reflux)
215
How do you name esters?
alcohol - yl carbox. acid - oate
eg propyl butanoate
216
What are some uses of esters?
Food flavouring
Perfumes
Solvents (they're polar liquids so polar organic compounds dissolve in them)
Plasticisers
217
How do you test for esters?
Smell them - usually smell sweet
218
Why are esters used as solvents in glues and printing inks?
Have low boiling points so can easily evaporate from mixtures
219
What is the problem with plasticisers over time?
They escape from the polymers causing the plastic to become brittle and stiff
220
How does the solubility of carboxylic acids vary with carbon chain length?
Solubility decreases as chain increases due to the longer non-polar hydrocarbon chain
221
Why are short chain carboxylic acids very soluble in water?
The highly polar carbonyl and hydroxyl groups can form hydrogen bonds with water
222
What has a higher boiling point alcohols or carboxylic acids and why?
Carboxylic acids as forms two hydrogen bonds between molecules (both carbonyl and hydroxyl group are polar) where as alcohols only have one
223
What is the reverse of esterification?
Hydrolosis
224
What is the hydrolysis of esters?
The splitting of esters by the action of water
225
What is the equation for the acid hydrolysis of esters?
ester + water ⇌ carboxylic acid + alcohol
(H+)
esters are not completely hydrolysed, an eqm. is set up
226
What are the conditions for acid hydrolysis of esters?
heat under reflux with dilute H2SO4
227
What hydrolysis of esters is faster, acidic or alkaline?
Alkaline
228
What is the equation for the alkaline hydrolysis of esters?
ester + base(aq) ---> carboxylate salt + alcohol
229
What are the conditions for the alkaline hydrolysis of esters?
heat under reflux with NaOH(aq)
230
What are vegetable oils and fats?
triesters
231
What is the equation for the production of vegetable oils and fats?
glycerol + 3 fatty acids ---> triglyceride + 3H2O
232
What is glycerol?
propane - 1,2,3 - triol
233
What are fatty acids?
Long chain carboxylic acids
234
Which of animal fats and vegetable oil is saturated and unsaturated?
Animal fats - saturated (no C=C)
Veg. oil - unsaturated
235
Why is vegetable oil liquid at room temperature and animal fats solid?
Animal fats are saturated so hydrocarbon chain fits nicely together which increases VDW
Veg oil is unsaturated so the hyrdocarbon chain is bent and doesn't pack together well which decreases the VDW
236
What is saponification?
Alkaline hydrolisis of fats into glycerol and the salts of the fatty acids present in the fat
237
What conditions are needed for saponification?
heat under reflux with NaOH(aq)
238
What is the reaction equation for saponification?
fat + 3NaOH ---> glycerol + 3 sodium salts (soap)
239
What is a soap and what properties does it have?
Salt of a long chain carboxylic acid
Hydrophobic and hydrophilic
240
What is biodiesel?
Renewable fuel made from vegetable oils (eg rapeseed and palm)
241
What is biodiesel made from?
Mixture of methyl esters of fatty acids
242
What is trans-esterification?
Reacting an ester with an alcohol to produce a different ester and a different alcohol (eg production of biodiesel)
243
What is the equation for the production of biodiesel?
triglyceride + 3 methanol ---> mixture of methyl esters (3) + glycerol
244
Glycerol is a bypoduct in the production of biodiesel, how can it be used?
Pharmaceuticals and cosmetics
245
What are acid derivatives?
Compounds that are related to carboxylic acids, the OH group has been replaced by something else
246
What are the three main derivatives?
acid anhydrides
acid chlorides
amides
247
What is the functional group of acid chlorides?
-COCl
248
How are acid chlorides named?
- anoyl chloride
249
How do acid chlorides react and why?
Violently/vigorously due to very polar -COCl group
250
How are acid anhydrides formed?
When two identical carboxylic acid molecules join together and water is eliminated
251
How are acid anhydrides named?
-anoic anhydride
252
What is the functional group of an amide?
- C(=O)N =
253
How do you name amides with the functional group -C(=O)NH2
-anamide
254
What is acylation?
The process in which an acyl group is added to a molecule
255
What is an acylating agent?
The molecule providing the acyl group
eg acyl chlorides
256
What type of mechanisms are acylations?
nucleophilic addition-elimination reactions
257
What is the reaction between acyl chloride and alcohol?
acyl chloride + alcohol ---> ester + HCl
258
What are the observations when acyl chloride reacts with alcohol?
Vigorous reaction which produces steamy fumes of HCl, smell of ester
259
What is the reaction between acid anhydrides and alcohol?
acid anydride + alcohol ---> ester + carboxylic acid
260
What are the conditions for acylation involving acyl chloride?
Anhydrous to prevent the hydrolysis of acyl chloride, reacts vigorously with water
261
What is the reaction between acyl chloride and water?
acyl chloride + water ---> carboxylic acid + HCl
262
What is the reaction between acid anhyrdride and water?
acid anhydride + water ---> 2 carboxylic acids
263
What is the reaction between acyl chloride and ammonia?
acyl chloride + ammonia ---> amide + HCl
HCl and excess ammonia can further react to make ammonium salt (NH4Cl)
264
What is the reaction between acid anhydride and ammonia?
acid anhydride + ammonia ---> amide + carboxylic acid
(Carboxylic acid and ammonia can further react to make ammonium salt)
265
What is a N-substituted amide?
When one of the hydrogens of an amine has been substituted
266
What is the reaction between acyl chloride and a primary amine?
acyl chloride + primary amine ---> n-sub. amide + HCl
267
What is the reaction between acid and anhydride and a primary amine?
acid anhydride + primary amine ---> n-sub. amide + carboxylic acid
(carboxylic acid will then react with the excess amine to produce a salt)
268
What type of organic compound is asparin and what is it made from?
ester
salicylic acid and ethanoic anhydride
269
What are the industrial advantages of using ethnic anhydride to acylate rather than ethanol chloride?
less corrosive
less vulnerable to hydrolysis (less reactive)
less hazardous to use as gives a less violent reaction
cheaper
doesn't produce corrosive HCl fumes
270
What is the molecular formula of benzene?
C6H6
271
What are the lengths of the carbon bonds in benzene?
All an intermediate length between carbon-carbon single and double bonds
272
Describe the bonds on each carbon atom in benzene, accounting for all 4 outer electrons?
Forms two carbon-carbon bonds either side
One carbon-hydrogen bond
The remaining outer electron from the p-orbital is delocalised to form a central ring above and below the ring of carbon atoms
273
Why is benzene more stable than the theoretical compound cyclohexa-1,3,5-triene?
Delocalised ring of electrons means the electron density is more evenly spread around the molecule which reduces electron repulsion
274
Why is the ΔH of hydration of benzene less exothermic than expected and what does a less exothermic reaction mean?
More energy must have been put in to break the bonds in benzene which suggests its more stable (due to the delocalised electron ring)
275
Does benzene favour substitution or addition?
Substitution
276
Why does benzene favour substitution reactions over addition?
In addition reactions the electrons from the delocalised system in benzene would need to bond with wahtevers being added so the delocalised ring would be broken so it would loose its stability
In substitution the organic product formed retains the ring of delocalised electrons
277
Why doesn’t benzene decolourise bromine water like you might expect it to?
Doesn't undergo an addition reaction as the delocalised ring would get broken
278
Whats an arene?
An aromatic compound - contains a benzene ring as part of its structure
279
What intermolecular forces does benzene have?
Only VDW
its a non-polar molecule
280
What type of reaction mechanism do you get when reacting something with benzene?
Electrophilic substitution
281
What is Friedel-Crafts acylation?
When the benzene ring acts as a nucleophile leading to an attack on R-COCl (makes phenylketones)
282
How does AlCl3 act as a catalyst in Friedel-Crafts acylation?
R-COCl + AlCl3 ---> R-C(+)O + AlCl4-
AlCl4- + H+ ---> HCl + AlCl3
makes a reactive intermediate
283
What is nitration?
When you warm benzene with conc. nitric and sulfuric acid and get nitrobenzene
284
What are the conditions for nitration?
conc. nitric and sulfuric acid
warmed
285
Show how you form the electrophile NO2 + from conc. nitric and sulfuric acid?
HNO3 + H2SO4 ---> H2NO3+ + HSO4-
HNO3+ ---> NO2 + + H2O
286
How do you get a monosubstitution in nitration?
temp 55°C as when temp is greater you get multiple substitutions
287
How are nitration reactions useful?
Nitro compounds can be used as explosives egTNT (trinitrotoluene or 2,4,6-trinitromethylbenzene
Nitro compounds formed can be reduced to form aromatic amines that are used to manufacture dyes and pharmaceuticals
Organic synthesis
288
What is the overall equation for the reaction between benzene and conc. nitric acid in the presence of a catalyst?
C6H6 + HNO3 ---> C6H5NO2 + H2O
289
What is the nitrile functional group?
C≡N
290
How can you 'prepare' primary amines?
Nucleophilic substitution of halogenoalkanes :NH3 acts as a nucleophile
reduction of nitriles
291
What are the conditions needed for the nucleophilic substitution of halogenoalkanes with ammonia to make primary amines?
heated in a sealed flask with excess ammonia in ethanol
292
What is the nucleophilic substitution reaction equation for halogenooalkanes and ammonia?
halogenoalkane + 2 ammonia ---> primary amine + ammonium salt
293
What are the two ways you can reduce a nitrile to make primary amines?
CATALYTIC HYDROGENATION
Hydrogen in the presence of a nickel catalyst with high temp and high pressure
STRONG REDUCING AGENT IN A NON-AQUEOUS SOLVENT
eg LiAlH4 in dry ether followed by dilute acid
294
Which method is preferred for making primary amines - nuc. sub of halogenoalkane with NH3 or reduction of nitriles?
Reduction of nitriles gives better yield as primary amine is only product
100% atom economy
295
How do you 'prepare' aromatic amines?
Reduction of nitro compounds
eg nitro benzene to make phenylamine
296
What conditions are needed when reducing nitrocompounds eg nitrobenzene?
heat under reflux with tin and excess conc. HCl, followed by addition of conc. NaOH
297
How are aromatic amines used?
To manufacture dyes
298
What is the inductive effect?
An electron pushing effect - alters the electron density distribution in a molecule
299
What is the inductive effect in benzene amines eg phenylamine?
Benzene ring draws the electron density away from the nitrogen, lone pair of electrons on the nitrogen get partially delocalised on the ring, so are much less available
300
What is the inductive effect in alkyl groups?
They push the electron density towards the atom so for example towards the nitrogen making the lone pair more available
301
What is base strength?
How available the lone pair of electrons are
302
What is the strongest and weakest base from ammonia, aromatic amine (phenylamine) and a primary amine?
strongest - primary amine (lone pair most available )
weakest - aromatic amines (lone pair least available)
303
Are amines strong or weak bases?
Weak
304
How do amines act as nucleophiles?
The lone electron pair on the N is attracted to δ+ regions
305
When do nucleophilic substitution reactions with halegonalkanes and amines stop and why?
When a quaternary ammonium ion has been formed (from sub. of tertiary amine) as it cannot act as nucleophile as there is no lone pair on the N
306
When carrying out nucleophilic substiturions to make amines with halogenoalkanes and ammonia how do you favour the production of primary amines?
Excess ammonia
This means its unlikely for a halogenoalkane to react with a primary amine and for further substitutions to occur as there are large amounts of ammonia available to react with instead
307
When carrying out nucleophilic substiturions to make amines with halogenoalkanes and ammonia how do you favour the production of quaternary ammonium salts?
Excess halogenoalkanes
This ensures all the ammonia will react with halogenoalkanes and then the amines formed will continue to react with the unused halogenoalkanes until quaternary ammonium salts have been made
308
How are quaternary ammonium salts used?
Cationic surfactants eg detergents, hair conditioner, fabric softners
As they have a positive and negative end meaning the two ends are attracted to other substances which prevents static from building up on surfaces
309
What is the equation for the nucleophilic addition-elimination reaction between acyl chlorides and amines?
acyl chlorides + amines ---> N-sub. amides + HCl
310
What is the equation for the nucleophilic addition-elimination reaction between acid anhydrides and amines?
acid anhydride + amine ---> N-sub. amide + carboxylic acid
311
What is a polymer?
A very long chain molecule comprising of several monomers
312
What is condensation polymerisation?
When two monomers form a link and a water molecule is lost
313
What are the three types of condensation polymers?
polyamides
polyesters
polypeptides
314
What are polyamides made from?
Dicarboxylic acids and diamines
315
Why are polyamides strong?
Commonly formed from long chain molecules which provides them with strength
316
What is an amide linkage?
-CONH -
(-C(=O)NH-) carboxyl groups of dicarboxylic acid and amino groups of diamines
317
What are the two polyamide examples?
Nylon 6,6
Kevlar
318
How is Nylon 6,6 used?
Clothing, carpet, rope, airbags, parachutes
319
What is Nylon 6,6 made from?
1,6-diaminohexane
hexanedioic acid
320
How is Kevlar used?
Bulletproof vests, boat construction, car tyres
321
What is Kevlar made from?
1,4-diaminobenzene
benzene-1,4-dicarboxylic acid
322
What are polyesters made from?
Dicarboxylic acids and diols
323
What is an ester linkage (in polyesters)?
-COO-
(-C(=O)O-) carboxyl groups of dicarboxylic acid and hydroxyl groups of diols
324
What is an example of a polyester?
Trylene (PET)
325
How is Trylene used?
Plastic bottles, clothing, sails
326
What is Trylene made from?
benzene-1,4-dicarboxylic acid
ethane-1,2-diol
327
What are polypeptides made from?
amino acids
328
How are condensation polymers broken down into their constituent molecules?
hydrolysis
329
What intermolecular forces do you get in condensation polymers?
VDW, permanent dipoles and hydrogen bonding
330
Why are condensation polymers stronger than addition polymers?
They have polar bonds eg C-N and C=O so they have hydrogen bonds as well as VDW
331
Why are addition polymers non-biodegradable?
Non-polar carbon chains which make them unreactive and inert
332
How do we dispose of addition polymers?
Have to be burned
333
Are condensation polymers biodegradeable?
Yes
334
Why are condensation polymers biodegradable?
They have polar bonds so they're susceptible to nucleophile attacks by water (hydrolysis)
(can be broken down by naturally occuring water and moisture)
335
What are the advantages of burying (landfill) polymers?
cheap and easy
336
What are the disadvantages of burying (landfill) polymers?
Plastic decomposes to release methane (greenhouse gas)
Takes up space
Takes a long time to decompose
337
What are the advantages of burning polymers to dispose of them?
Gets rid of them
Heat can be used to generate electricity
338
What are the disadvantages of burning polymers to dispose of them?
Can release toxic gas which has to be removed
CO2 produced which is a greenhouse gas
339
What are the advantages of recycling polymers?
Cuts down on landfill
Saves raw materials (oil is non-renewable)
Produces less CO2 than burning plastic
340
What are the disadvantages of recycling polymers?
Labour intensive sorting plastic
Expensive (costs more than landfill)
Plastic can become contaminated
341
What does NMR stand for?
Nuclear Magnetic Resonance
342
What is NMR spectroscopy?
An analytical technique that allows the structure of a molecule to be determined by analysing the energy of each bond environment
343
When does an atom have nuclear spin and what does this cause the atom to have?
When there is an odd number of nucleons in its nucleus and causes it to have a weak magnetic field
344
What does an atoms environment depend on?
All the groups its connected to, going right along the molecule
345
What is NMR actually measuring?
Normally nuclei spin in random directions (so their magnetic field cancels out) but when placed in a strong external magnetic field they either align with the field or opposed to it.
Nuclei aligned with the field are at a slightly lower energy level.
Radio waves of the right frequency can give those nuclei enough energy to flip up to the higher energy level
NMR can measure the adsorption of the sample
346
What does chemical shift depend on?
The molecular environment
347
What is chemical shift measured in?
δ
parts per million relative to TMS
348
What is the structure of TMS?
Si (CH3)4
tetramethylsilane
349
What does a peak at δ=0 on a NMR spectra graph mean?
TMS has been added to the sample
350
Why is TMS sometimes added too samples when using NMR spectroscopy and what properties make it okay to add?
Calibration purposes
Inert, non-toxic, volatile (won't react with sample and can be easily removed)
351
What does the area under each peak on a proton NMR spectra represent?
Corresponds to the relative no. of H atoms in each environment
352
What does the no. of splits in a peak on a proton NMR show?
The no. of hydrogen atoms on the adjacent carbon
353
What three things do you need to look at when studying a proton NMR spectra?
Chemical shift value
Ratio of the areas under peaks
Splitting patterns
354
What do we use when the area under the peaks on a proton NMR are too difficult to distinguish?
Integration trace
Shown instead and the heights are proportional to the no. of H atoms in each environment
355
What must be done to samples when carrying out proton NMR?
Dissolved in non-hydrogen containing solvents
(must be non-hydrogen so it doesn't produce any δ peaks)
356
What solvents can be used to dissolve proton NMR samples? examples and why
CCl4 (doesn't contain any hydrogens)
Deuterated solvents (2H atoms as they have 2 nucleons so have no nuclear spin and ∴ no magnetic field)
357
What is chromatography?
An analytical technique used to separate and identify component molecules of a mixture
358
What does the separation in chromatography depend on?
The solubility in the mobile phase
The retention by the stationary phase
359
What is the mobile phase in chromatography and what state is it in?
When the molecules can move
Liquid or gas
360
What is the stationary phase in chromatography and what state is it in?
When the molecules can't move
Solid or a liquid on a solid support
361
How does solubility affect the distance moved by a compound in chromatography?
More soluble the further it moves with the mobile phase
362
How does a compounds affinity to the stationary phase affect the distance it moves in the mobile phase?
The greater the affinity the shorter the distance moved
363
What are the three types of chromatography?
Thin Layer Chromatography (TLC)
Column Chromatography
Gas Chromatography
364
What is Thin Layer Chromatography used for?
Separating mixtures
365
Describe the set up of Thin Layer Chromatography and the reasoning for certain elements
A metal plate with a thin layer of silica (or alumina) is placed in a beaker with solvent. Solvent is below the baseline (where mixture being tested is) so that it doesn't dissolve the sample
Watch glass lid is placed on beaker to prevent the solvent from evaporating
366
What do you do with the TLC plate once the solvent has travelled to the top of the plate?
Remove plate from beaker
Use a pencil to mark how far the solvent travelled - this line is the solvent front
Place the plate in a fume cupboard and leave it to dry (fume cupboard prevents any toxic or flammable gases from escaping the room)
367
What is the solvent front in TLC?
Where the solvent travelled to on the TLC plate
368
What is a chromatogram and how is it used?
The product of TLC and the position of spots on a chromatogram can be used to calculate Rf values and determine the components of a mixture
369
What do you need to do if carrying out TLC with colourless chemicals?
Use a TLC plate with a special fluorescent dye that glows when UV light shines on it
Expose the chromatogram to iodine vapour (its a locating agent so sticks to chemicals and shows them as brown spots)
370
How do you expose a chromatogram to iodine vapour?
Leave it in sealed jar with a couple of iodine crystals
371
How do you calculate the Rf value?
Rf = distance moved by molecule / distance moved by solvent
372
What do Rf values depend on?
Specific molecule
Composition of TLC plate
Composition of solvent
Temperature
373
What does the number of spots on a chromatogram tell you?
The no. compounds present in a mixture
374
What is Column Chromatography used for?
To seperate out solutions
375
How is Column Chromatography set up?
A vertical glass column is set up with a solid, powdered substance (eg aluminium oxide) that acts as the stationary phase.
A solvent containing the mixture being separated is then added tot he column and moves down.
Each compound moves at different speeds so is collected at different times
376
Why do different molecules drain out the column during Column Chromatography at different times?
Varying affinities of the molecules to the stationary phase means they have different retention times
377
How can molecules be identified from Column Chromatography?
The different retention times can be compared to known values
378
How is Gas Chromatography used?
To separate mixtures of volatile liquids?
379
What is the stationary phase of Gas Chromatography?
Solid or a solid coated in a viscous liquid that's been packed into a long tube that is built into an oven
380
What is the mobile phase of Gas Chromatography?
Unreactive gas (eg nitrogen)
381
Describe the setup of Gas Chromatography and explain the reasoning for some of the elements
A tube thats coiled up to save space in a temp. controlled oven so that it can happen under pressure and at a high constant temp.
The carrier gas is fed into the tube and the sample is also injected into the tube
The other end of the tube is attached to a detector and recorder
382
What does the retention time of Gas Chromatography depend on?
How much time the molecule spends moving along with the carrier gas and how much time it spends stuck to the viscous liquids
383
What does the detector and recorder of Gas Chromatography produce?
A graph of recorder response against retention time
Each molecule has a unique retention time that can be compared to known retention times
Area under each peak tells you the relative amount of each compound present in the mixture
384
What are some uses of Gas Chromatography?
Find the level of alcohol in blood or urine (accurate enough to be used as evidence in court)
Find proportion of various esters in oils used in paints. Picture restorers then know exactly what paint was originally used)
385
What can you combine with Gas Chromatography to make a very useful analytical technique?
Mass Spectrometry
386
How does Gas Chromatography - Mass Spectrometry (GC-MS) work?
A sample is separated using Gas Chromatography but instead of going to a detector, the separated components are fed into a mass spectrometer
387
What are the advantages of Gas Chromatography - Mass spectrometry?
The components separated out can be positively identified
Computers can be used to match the mass spectrum for each component of the mixture against a database - the process can be automated
