Organic Flashcards
(178 cards)
1
Q
Define empirical formula
A
The simplest whole number ratio of atoms in a molecule
2
Q
Define molecular formula
A
Gives the actual number of atoms of different elements in a molecule
3
Q
Define displayed formula
A
Shows every atom and every bond in a molecule
4
Q
Define structural formula
A
Shows arrangement of atoms in a molecule without showing every bond
5
Q
Define skeletal formula
A
Drawn as lines with each vertex being a carbon atom. Carbon atoms not drawn, assumed each atom has all unspecified bonds as C-H
6
Q
Give the suffixes for:
An alkane
An alkene
An alcohol
An aldehyde
A ketone
A carboxylic acid
A
-ane
-ene
-ol
-al
-one
-oic acid
7
Q
Give the prefixes for:
CH3 group
C2H5 group
C3H7 group
C4H9 group
Cl group
Br group
I group
A
•Methyl-
•Ethyl-
•Propyl-
•Butyl-
•Chloro-
•Bromo-
•Iodo-
8
Q
Define structural isomerism
A
When molecules have the same molecular formula but different structural formula
9
Q
What is positional isomerism?
A
Functional group is attached to the main chain at a different place
10
Q
What is functional group isomerism?
A
Same atoms but different functional group due to a different arrangement of atoms
11
Q
What is a chain isomerism?
A
Hydrocarbon chain organised differently e.g branched chains
12
Q
Define stereoisomerism
A
When molecules have the same structural and molecular formula, but have a different arrangement of atoms in space
13
Q
What is E-Z isomerism?
A
Is caused by the limited rotation about c=c double bonds
14
Q
How are E and Z isomers decided?
A
If the 2 substituents with the highest molecular formula mass are on same side of double bond, it is the Z (zusammen) isomer
If they’re on different sides it is the E (entgegen) isomer
15
Q
What is an alkane?
A
A saturated hydrocarbons containing C-H bonds only
16
Q
What’s the general formula of an alkane?
A
CnH2n+2
17
Q
Are the bonds in alkanes polar/non polar? Why?
A
Non-polar: Carbon and hydrogen have similar electronegativities
18
Q
Which intermolecular forces do alkanes have and why?
A
Only VDW forces of attraction as bonds are non-polar
19
Q
Are alkanes soluble in water? Why?
A
Insoluble as hydrogen bonds in water are stronger than alkanes’ VDW forces of attraction
20
Q
How reactive are alkanes?
A
Very unreactive
21
Q
Which reactions will alkanes undergo?
A
Combustion and reaction with halogens
22
Q
What is crude oil?
A
Mixture of fractions (hydrocarbons with similar boiling points and properties)
23
Q
How is crude oil formed? Is it renewable?
A
Formed at high temps and pressures deep below earth’s surface over millions of years
Therefore non renewable
24
Q
Name the fractions from high to low boiling points
A
Gases - fuel on site
Gasoline/petrol/naphtha - cars
Kerosene/paraffin - jet fuel, lighting
Diesel oil - lorries/taxis
Lubricating oil/waxes - candles, engine oil
Fuel oil - ships, power stations
Tar/bitumen - roads/roofing
25
What is fractional distillation?/how does it work?
crude oil heated until mostly vaporised
Passed into a fractionating tower thats cooler at top than the bottom
liquid fractions are piped off the at the bottom
Vapours rise up the column & -via trays&bubblecaps- condense when temp
26
What is fracking and how is it done?
Natural gas held within shale rock
Drill into shale, force pressurised water and sand into rock to fracture it, collect gas
HCl and methanol added to break up shale and prevent corrosion
27
What are the advantages of fracking?
Gas supply for many years
Reduces imported gas and electricity
28
What are the disadvantages of fracking?
Lots of traffic to the local area
Concern about amount of water used
Chemical additives can pollute water supplies
Can cause small earthquakes
Combust CH4->CO2->global warming
29
Why are alkanes cracked?
To turn a long chain alkane (not economically viable) into a shorter chain alkane and an alkene (more reactive, starting point for many products)
30
Why is a shorter chain alkane more economically viable?
As they can be used as a fuel
31
What are the conditions for thermal cracking?
700-1200 K temperature
Up to 7000kPa pressure
32
What is the intermediate for the reaction?
Free radicals
33
What are the main products for thermal cracking?
alkenes
34
What are the conditions for catalytic cracking?
Lower temp (720K)
Lower pressure (but above atmospheric)
Zeolite catalyst (SiO2 and Al2O3) with a honeycomb structure to give a large surface area
35
What are the main products of catalytic cracking?
Cycloalkanes, aromatic hydrocarbons, branched alkanes
36
Write an equation for the combustion of propane
C3H8 + 5O2 —> 3CO2 + 4H2O
37
What is a fuel?
Something which releases heat energy when combusted
38
What are the 5 main fuels comprising of alkanes?
Methane, Butane, Propane, petrol (about C8), paraffin (C10-C18)
39
What is incomplete combustion? What products are formed in the case of alkanes?
Combustion in a limited supply of oxygen
CO - carbon monoxide- poisonous
C - carbon - soot - global dimming
40
Which type of hydrocarbons are most likely to undergo incomplete combustion?
Longer chains
41
What is the environmental impact of carbon monoxide?
It’s toxic/poisonous
42
What is the environmental impact of nitrogen oxides?
Forms nitric acid -> acid rain, photochemical smog
43
What is the environmental impact of sulfur impurities/ sulfur dioxide?
Forms sulphuric acid -> acid rain
44
What is the environmental impact of soot (carbon)?
asthma, global dimming, cancer
45
What is the environmental impact of unburnt hydrocarbons?
Photochemical smog
46
What is the environmental impact of carbon dioxide?
greenhouse gas-> global warming,
increases local temperatures,
speeds up climate change
47
What is the environmental impact of water vapour?
greenhouse gas-> global warming,
increases local temperatures,
speeds up climate change
48
What are flue gases?
Gases given out by power stations
49
Write 2 equations for 2 different ways of desulfurising flue gases
CaO(s)+2H2O(l)+SO2(g)+1/2O2(g)—> CaSO4 2H2O(s)
or
CaCO3(s)+SO2(g)+1/2O2(g)—> CaSO4+CO2(g)
50
What are catalytic converters made up of?
Ceramic honeycomb coated with platinum, palladium and rhodium metals
51
What do catalytic converters catalyse (equations)?
They catalyse these reactions of products from car exhausts
2CO(g)+2NO(g)—>N2(g)+2CO2(g)
Hydrocarbons+NO—>N2+CO2+H2O
52
What are greenhouse gases?
Gases which trap infrared radiation, making the earth act like a greenhouse
53
What is the greenhouse effect and how does it contribute to global warming?
Greenhouse gases trap infrared radiation in atmosphere, atmosphere heats up —> global warming
54
Define carbon neutral activities?
Activities that produce no net/overall carbon dioxide emissions
55
How are halogenoalkanes formed from alkanes?
Free radical substitution reaction
56
What are the 3 stages of free radical substitution?
•Initiation-breaking halogen bond to form free radicals
•Propagation-chain part of the reaction where products are formed but free radical remains
•Termination-free radicals removed, stable products formed
57
What are the conditions needed for the formation of a free radical chlorine atom?
Presence of UV light
58
Write equations for the reaction of CH4 with Cl2 to form CH3Cl
initiation:Cl2–>2Cl• (in presence of UV light)
propagation:Cl•+CH4–>HCl+•CH3
•CH3+Cl2–>CH3Cl+Cl•
Termination: •CH3+Cl•->CH3Cl
2Cl•->Cl2
•CH3+•CH3->CH3CH3
59
What is the ozone layer’s function?
Protects the earth from harmful exposure too too many UV rays
60
How do CFC’s break the ozone layer down?
Free radical substitution
61
Write an equation for the overall decomposition of ozone into oxygen (O2)
2O3 —> 3O2
62
Write free radical substitution equations to show how Cl free radicals catalyse the decomposition of O3
Cl2 -> 2Cl (in presence of UV light)
Cl•+O3 -> ClO•+O2
ClO•+O3 -> 2O2+Cl•
Overall: 2O3 -> 3O2
63
Are halogenoalkanes soluble in water?
Insoluble as C-H bonds are non-polar, not compensated for enough by C-X bond polarity
64
Do halogenoalkanes have a polar bond? Why?
Yes polar, as halogen has a higher electronegativity than C (halogen os delta-, Carbon is delta+)
65
Which intermolecular forces do halogenoalkanes have? Why?
Permanent dipole-dipole and VDW forces of attraction
C-X bond polarity creates permanent dipoles
66
When would halogenoalkanes have higher melting points?
Increase Carbon chain length
Halogen further down group 7
67
How would the mass of a haloalkane compare with the mass of an alkane of the same chain length?
Greater because mass of halogen > mass of H
68
What is the most important in determining haloalkanes reactivity?
Carbon-halogen bond enthalpy
69
What is the order of reactivity of halogenoalkanes?
Although C-F is most polar bond, the bond enthalpy of C-X decreases down the group so reactivity increases down the group
70
What is a nucleophile?
A negatively charged ion/delta- atom with a lone pair of electrons which can be donated to an electron deficient atom
71
Give 3 examples of nucleophiles
:OH-
:CN-
:NH3
72
What is nucleophilic substitution?
A reaction where a nucleophile donates a lone pair of electrons to delta+ C atom, delta- atom leaves molecule (replaced by nucleophiles)
73
Draw the mechanism for the reaction of bromoethane with NaOH (aq)
H H
| |/\
H-C-C-Br
| | \
H H \ :OH-
74
Draw the mechanism for the reaction of bromoethane with NH3
H H H H H
| |/\ | | |+
H-C-C-Br —> H-C-C-N-H /
| | \ | | | \/
H H \ :NH3 H H H
75
What are CFC’s?
Chlorine-fluoro-carbons - haloalkanes containing C, F and Cl only (no H)
76
What is the problem with CFC’s?
Although unreactive under normal conditions, they catalyse they catalyse the breakdown of ozone in the atmosphere via free radical substitution
77
What are CFC’s being replaced with?
HCFC’s (hydrogen, chlorine, fluorine, carbon)
HFC’s (hydrogen, fluorine, carbon)
78
What are the conditions/reactants needed for the elimination reaction of alkanes?
NaOH or KOH dissolved in ethanol (no water present)
Heated
79
What is formed in the elimination reaction of haloalkanes?
An alkene, water and halogen ion
80
What is an alkene?
Unsaturated bonds with a C=C double bond
81
What is the general formula of an alkene?
CnH2n
82
Why is there no rotation about the C=C double bond?
Due to the pi orbital - electron density above and below the single bond, which holds the carbon atoms in place
83
Are alkenes more or less reactive than alkanes? Why?
More reactive due to high electron density of double bond and the fact the pi-bond is slightly easier to break
84
What intermolecular forces of attraction do alkenes have?
Only VDW forces due to non-polar bonds
85
Are alkenes soluble in water? Why?
No, non-polar bonds (VDW’s < hydrogen bonding)
86
Name the 3 kinds of isomers alkenes have
Chain isomers (branched chains)
Position isomers (C=C on different Carbon atoms)
Geometric E-Z isomers
87
Write an equation for the complete combustion of pent-2-ene
CH3CH=CHCH2CH3 + 7.5O2 —> 5CO2+5H2O
88
What is an electrophile?
Electron deficient atoms/ions which accept a pair of electrons (here, from the C=C double bond)
89
What is the most stable type of carbocation intermediate? Why?
Alkyl groups have a positive inductive effect,so the most stable carbonation is the one bonded to the most other carbon atoms (i.e tertiary carbocation)
90
Major products will be formed from which kinds of carbocations?
Tertiary (or the most stable available)
91
What conditions are needed for the electrophilic addition of H2O to an alkene?
Acid catalyst, usually phosphoric acid
92
What are the products of the electrophilic addition of H2O to an alkene reaction?
An alcohol
93
What conditions are needed for the electrophilic addition of a hydrogen halide to an alkene?
Room temperature
94
What conditions are needed for the electrophilic addition of a halogen molecule to an alkene?
Room temperature and organic solvent
95
How does a molecule with a non-polar bond react as if it is an electrophile?
C=C double bond with a high electron density induces a temporary dipole in the halogen molecule—>delta+ atom attracted to double bond
96
How would you turn the product (from sulphuric acid+ethene) into an alcohol and how does this show that sulfuric acid catalyses the addition of water to an alkene?
Add water
H2SO4 reforms showing it catalyses the addition of alkenes
97
What is an addition polymer?
Many monomers bonded together via rearrangement of bonds without the loss of any atom or molecule
98
What are monomers? What form do they usually take?
Molecules which combine to form a polymer
Usually have a C=C bond which breaks to leave a repeating pattern
99
Give 3 uses of poly(chloroethene)/PVC
Drainpipes
Vinyl
Aprons
100
Give 2 examples of plasticisers
esters and phthalates
101
What are plasticisers?
Small molecules that get between polymer chains to force them apart and allow them to slide over one another
102
How do the physical properties of PVC change due to a plasticiser? What applications does this lead to?
PVC with a plasticiser becomes flexible , used for aprons
Without a plasticiser, PVC is rigid, used for drainpipes
103
Why do things containing mainly C-C and C-H bonds not decompose easily?
Bonds are non-polar so are not attacked by enzymes
104
Why is a lack of biodegradability in compounds with C-C or C-H bonds a problem?
Disposal is very problematic
105
What is mechanical recycling?
Where plastics are separated into different types, washed, ground down, melted and re-moulded
106
What is mechanical recycling used for?
Soft drinks bottles —> fleeces
107
What is feedstock recycling?
Plastics heated to a temperature which break polymer bonds, leaving original monomers that can be made into new plastics
108
What is feedstock recycling used for?
Making totally new plastics
109
What is a problem with recycling?
Each time thermosoftening plastics are melted and remoulded, their properties degrade, so they can only be remoulded a limited number of times
110
What is the functional group of an alcohol?
Hydroxyl group -OH
111
What is the general formula of am alcohol?
CnH2n+1OH
112
How do you name alcohols (one prefix, one suffix)?
Hydroxyl- or -OH
113
What kind of intermolecular forces do alcohols have? Why?
Hydrogen bonding due to the electronegativity difference in the OH bond
114
How do alcohols’ mpt and bpt compare to other hydrocarbons’ of similar C chain lengths? Why?
Higher, because they have hydrogen bonding—> Stronger than VDW forces
115
Are alcohols soluble in water? Why does solubility depend on chain length?
Soluble when short chain - OH hydrogen bonds to hydrogen bond in water
Insoluble when long chain - non-polarity of C-H bonds take precedence
116
What makes an alcohol primary?
C bonded to OH is only bonded to one other C atom
117
What makes an alcohol secondary?
C bonded to OH is bonded to 2 other C atoms
118
What makes an alcohol tertiary?
C bonded to OH is bonded to 3 other C atoms
119
How can ethanol be made from crude oil?
Hydration of ethene via electrophilic addition (phosphoric acid catalyst H3PO4)
120
What are the advantages and disadvantages of making ethanol from crude oil?
Advantages: fast,continuous process, ethanol has a high purity
Disadvantages: non renewable as from crude oil
121
How can ethanol be made by fermentation?
Plant carbohydrates broken down and fermented by enzymes in yeast —> ethanol
122
What conditions are needed for the reaction to make ethanol by fermentation?
Enzymes in yeast as a catalyst, 35°C, anaerobic conditions
123
Write an equation for the reaction that takes place when ethanol is made by fermentation
C6H12O6(aq)—>2C2H5OH + 2CO2
124
What are the advantages and disadvantages from making ethanol by fermentation?
Advantages: renewable as from plants
Disadvantages: slow,batch process, enzymes stop working at 15% alcohol so solution isn’t pure, needed to be fractionally distilled
125
In the future, how might most ethene be made? Why isn’t it made like this at the moment?
Dehydrate ethanol made by fermentation —> ethene
Not economical at the moment
126
Define carbon neutral
No net addition of CO2 to the atmosphere - CO2 released when combusted = CO2 absorbed as a plant
127
Explain how using ethanol in petrol engines could be considered to be carbon neutral?
CO2 released in fermentation and combustion = CO2 absorbed when growing
128
Why would it be probably not be entirely carbon neutral to use ethanol in petrol engines?
Other “carbon costs” associated with it eg transport
129
What is a commercial fuel that uses ethanol? What else does it contain and why?
Methylated spirits - methanol (toxic so cant be drunk)
130
Write an equation for the combustion of ethanol
C2H5OH(l)+3O2(g)—>2CO2(g)+3H2O(l)
131
What is an elimination reaction?
The removal of a smaller molecule from a larger one
132
Which group leaves the parent molecule in the case of alcohols?
OH and a H (to form water)
133
What physical conditions are needed for the elimination reaction from alcohols to alkenes? (2 alternatives)
Excess hot concentrated sulphuric acid or pass vapour over hot aluminium oxide
134
What forms if you partially oxidise a primary alcohol?
An aldehyde
135
What conditions are needed to partially oxidise a primary alcohol?
Dilute sulphuric acid, potassium dichromate (VI), distill product as it’s produced, gentle heating
136
Write an equation for the partial oxidation of ethanol
CH3CH2OH(l)+[O]—>CH3CHO(g)+H2O(l)
137
What forms if you fully oxidise a primary alcohol?
A carboxylic acid
138
What conditions are needed to fully oxidise a primary alcohol?
Concentrated sulphuric acid, potassium dichromate (VI), reflux for about 20 mins, strong heating
139
Write an equation for the full oxidation of ethanol
CH3CH2OH(l)+2[O]—>CH3COOH(g)+H2O(l)
140
What forms if you oxidise a secondary alcohol?
A ketone
141
Why can alcohols not be oxidised further and why cant tertiary alcohols be oxidised?
A carbon-carbon bond would have to break
142
What conditions are needed for the oxidation of a secondary alcohol?
Concentrated sulphuric acid, potassium dichromate (VI), reflux about 20 mins, strong heating
143
Write an equation for the oxidation of propan-2-ol
CH3CH(OH)CH3(l)+[O]—> CH3COCH3(g)+H2O(l)
144
What is an aldehyde? What is its functional group?
Molecule with C=O group at the end of a carbon chain, carbonyl functional group (C=O)
145
How do you name aldehydes? Give an example
Suffix -al
eg. ethanal
146
What is a ketone? What is its functional group?
Molecule with C=O group in the middle of a carbon chain, carbonyl functional group (C=O)
147
How do you name ketones? Give an example?
Suffix -one
eg. propanone
148
What is a carboxylic acid? What is its functional group?
Molecule with a COOH group, which has to be at the end of a carbon chain
Carboxyl functional group (made up of a carbonyl C=O and hydroxyl -OH group)
149
How do you name carboxylic acids? Give an example?
Suffix -oic acid
eg. propanoic acid
150
What does the Tollens’ test give a positive result for?
Aldehydes
151
What is in Tollens’ reagent? How does this react with the substance to be tested?
Silver nitrate in NH3 (aq) - oxidises aldehydes but not ketones
Complex silver (l) ions reduced to Ag(s)
152
How do you carry out the Tollens’ test?
Add equal volumes of substance being tested and tollen’s reagent to a test tube, leave in water bath for 10 mins and observe any changes
153
What is the result of the Tollen’s test for aldehydes and ketones?
Aldehydes - silver mirror forms (solid Ag)
Ketones - no visible change
154
What does Fehling’s solution give a positive result for?
Aldehydes
155
What is in Fehling’s? How does this react with the substance to be tested?
Blue copper (II) complex ions - gentle oxidising agent
Reduced to Cu+ ions (brick red)
156
What conditions do you need to use the Fehling’s solution?
Heat
157
What result do aldehydes and ketones give in the Fehling’s test?
Aldehydes - brick red ppt
Ketones - no visible change
158
How do you test for alkenes? What is the result?
Shake with bromine water, result is bromine water is decolourised (orange to colourless)
159
How do you test for haloalkanes? What is the result?
Add NaOH(aq) and warm, acidify with HNO3, add AgNO3(aq)
Result: precipitate of AgX (for Cl=white, for Br=cream, for I=yellow)
160
How do you test for alcohols? What is the result?
Add acidified K2Cr2O7 (potassium dichromate (VI)) and heat
Result: colour change from orange to green for primary and secondary alcohols (no change for tertiary alcohols)
161
How do you test for aldehydes? What is the result? (2 ways)
1. Warm with Fehling’s solution, result: brick red ppt forms (from blue solution)
2. Warm with Tollen’s reagent, result: “silver mirror” (Ag(s) ppt) forms
162
How do you test for carboxylic acids? What is the result?
Add NaCO3 (aq), result: CO2 (g) given off - effervescence
163
What is mass spectrometry? How does it work?
Used to find RMM of organic compounds
Compound is dissolved in solution, ionised by high voltage supply (to mostly 1+ ions), accelerated by a negatively charged plate, becomes beam of ionised molecules, reach detector&cause a current to flight. ToF used to work out m/z value and plot a graph
164
What does the x axis show on a mass spectrum? What does this effectively show and why?
Shows m/z value (mass divided by ionic charge)
Since most ions are 1+, this effectively shows Mr
165
Why are there multiple peaks when molecules are put into a mass spectrometer?
The molecular ion is shown as a peak, but it will also fragment into smaller molecules, so these peaks are shown as well
Also, due to isotopes of atoms, different peaks may be seen
166
How does chromatography work and what does it tell you?
A stream of gas carries a mixture of vapours through a column packed with solids, different compounds move through different speeds, so they’re separated. The amount of each compound can then be measured
167
What does GCMS stand for?
Gas chromatography linked to mass spectrometry
168
What might GCMS be used for?
Powerful chemical analysis - forensic work, measuring water pollution, drug testing on athletes, racehorses
169
What is high resolution mass spectrometry?
Mass spectrometers which give Mr to 3dp or 4dp are called high resolution (low resolution is given to nearest whole number)
170
What does a high resolution mass spectrometer allow you to do?
Distinguish between compounds that have the same Mr to nearest whole number, but are made up of different atoms and so have different values of Mr to 3dp
171
Why do atoms and chemical bonds absorb infrared radiation?
They’re constantly vibrating - they can absorb infrared radiation that’s the same frequency as their frequency of vibration
172
What effect does a stronger bond have on the frequency of vibration?
Vibrate faster (with higher frequency)
173
What effect do heavier atoms have on frequency of vibration?
Vibrate slower (with lower frequency)
174
How does infrared spectroscopy work?
Every bond has a unique vibration frequency in the infrared region of the EM spectrum.
Bonds absorb radiation that has the same frequency as their frequency of vibration.
Infrared radiation emerged from a sample is missing the frequencies that have been absorbed (info can be used to identify the compounds functional group)
175
What happens inside an infrared spectrometer?
Beam of infrared radiation with a range of frequencies is passed through a sample
Radiation that emerges is missing frequencies that have been absorbed by the bonds in the sample
Graph is plotted of intensity against frequency of radiation
176
What do the troughs on an infrared spectrum show?
The frequencies where radiation has been absorbed - match to table to find out which bonds they represent
177
What is the fingerprint region?
Area on the infrared spectrum below wavenumber of 1500cm-1
Many peaks, caused by complex vibrations of the whole molecule. Unique to every compound, so can be used to identify compounds
178
How is the fingerprint region used to identify compounds?
The fingerprint region’s pattern is matched to a database on a computer to identify the compound accurately
