TOPIC 6 - Organic chemistry I Flashcards
(121 cards)
1
Q
What is a general formula?
A
2
Q
What is the general formula for alkanes?
A
CnH2n+2
3
Q
What is the general formula for alkenes?
A
CnH2n
4
Q
What is the general formula for alcohols?
A
CnH2n+1OH
5
Q
What is the molecular formula?
A
6
Q
What is the empirical formula?
A
7
Q
What is the structural formula?
A
8
Q
What is the skeletal formula?
A
9
Q
What is the displayed formula?
A
10
Q
What is a homologous series?
A
11
Q
What is the functional group for alkenes?
A
C=C
12
Q
What is the functional group for alcohol?
A
-OH
13
Q
What is the functional group for an aldehyde?
A
R-C=O
(double bond with oxygen at the end of the carbon chain)
14
Q
What is the functional group for ketones?
A
Double bond with oxygen in the middle of te carbon chain.
15
Q
What is the functional group for carboxylic acids?
A
COOH
(double bond with O and single bond with OH)
16
Q
What is the formula for cyclopentane?
A
C5H10
17
Q
What is a polymerisation reaction?
A
18
Q
What is a hydrolysis reaction?
A
19
Q
What is an elimination reaction?
A
20
Q
What is an addition reaction?
A
21
Q
What is a substitution reaction?
A
22
Q
What does a curly arrow in a mechanism show?
A
The movement of a pair of electrons
23
Q
What is the mechanism for the reaction of OH- with bromoethane?
A
24
Q
What type of reaction is this?
A
Nucleophilic substitution
25
What is heterolytic fission?
26
What is homolytic fission?
27
What is the initiation step of this reaction?
28
What is the propagation step of this reaction?
29
What is the termination step for this reaction?
30
Can we make only chloromethane with free radical substitution of chlorine with methane?
No. The chain reaction will keep going and di- and trichloromethane can be formed apart from chloromethane.
However adding excess methane can help to get just chloromethane.
31
How is crude oil separated using fractional distillation?
Give the range of temps used.
32
What is the use of the gas (shorter) fraction?
33
What is the use of the petrol fraction?
34
What is the use of the kerosene?
\*Kerosene\*
35
What is the use of diesel oil?
36
What is the use of fuel oil?
37
What is the use of bitumen?
38
Why do we use cracking?
Larger fractions are broken into lighter, more demanded fractions.
39
What are the conditions for thermal cracking?
40
What type of products does thermal cracking produce?
41
What are the conditions for catalytic cracking?
42
What are the typical products of catalytic cracking?
43
What are the advantages of catalytic cracking?
Lowers temperature and pressure needed.
Lowers the cost and speeds up the reaction.
44
Why are alkanes reformed?
To avoid knocking, which is when straight chain alkanes explode upon compression. This reduces the efficiency of the engine. Therefore they are turned into branched and cyclic alkanes to increase the efficiency.
45
What are the conditions for reforming alkanes?
Platinum catalyst (Pt)
46
How does burning hydrocarbons cause acid rain?
* Sulfur impurities are burnt and so SO2 is produced. The sulfur dioxide then reacts with water in the atmosphere to create sulfuric acid.
* Nitrogen and oxygen react in the high temp/pressure inside the engine and create NOx which then reacts with water in the atmosphere to create nitric acid.
47
Why is there E/Z isomerism in some alkenes?
Atoms can't rotate around the carbon double bond.
48
What do the CIP rules say to naming geometrical isomers?
Take into account the groups whose first element directly bonded to the carbon has the highest atomic number.
If they are the same, take into account the next element.
49
What does E mean in geometrical isomerism?
The groups are in different sides (trans)
50
What does Z mean in geometrical isomerism?
The groups are in the same side (cis)
51
What is an electrophile?
An electron pair acceptor, a species that lacks electrons.
52
What is the generic mechanism for the electrophilic addition of to alkenes?
53
What are the conditions for the addition of hydrogen (hydrogenation/saturation) of alkenes?
150ºC and Nickel catalyst.
54
What is the test for alkenes?
Add bromine water to alkene. If the alkene is present, the mixture should turn from brown-orange to colourless.
55
What is the mechanism for the addition of bromine to alkenes?
56
What is the product for the hydration of alkenes?
Alcohols
57
What are the conditions for the hydration of alkenes?
Steam+alkene.
Phosphoric acid catalyst.
300ºC and 60atm.
58
Is the yield high for the hydration of alkenes?
At first no, the reaction is reversible with a yield of 5%. However the alkene is recycled and the overall yield is 90-95%.
59
What is the product of an alkene with acidified potassium manganate?
Alcohol (diol)
60
What is the colour change for the oxidation of alkenes into diols using acidified potassium manganate?
Purple to colourless.
61
What is added to alkenes to form a halogenoalkane?
(not free radical substitution)
Hydrogen halide.
62
What is the mechanism for the reaction between alkenes and hydrogen halides?
63
What is the order in stability of the different carbocations?
64
Why are seconary and tertiary carbocations more stable?
Alkyl groups push electrons towards the positive carbon making it more stable so it has a higher chance of being formed.
65
In the reaction of prop-1-ene with hydrogen bromide, which is the major product: 2-Bromopropane or 1-bromopropane?
Why?
66
Show the addition polymerisation of propene to create poly(propene).
67
How can plastics be recycled?
Some, like poly(propene) can be re-moulded into new objects.
Others are cracked into its monomers and the monomers are used to make more plastic.
68
What are the advantages of incinerating plastics?
Heat produced can be used to generate electricity.
Avoid incorrect disposal of plasics (since they aren't biodegradable)
69
What is a disadvantage of incinerating plastics and how is it fixed?
Toxic gases can be released (like HCl, released by burning PVC)
Flue gas scrubbers are used to neutralise acidic gases (like HCl) by firing a base at the gases.
70
What metals do catalytic convertes often contain?
Platinum, rhodium and iridium metals
71
WHat do catalytic converters do?
* Convert carbon monoxide to carbon dioxide.
* Covert NOx into nitrogen and oxygen.
* Burn unburnt hydrocarbons into water and carbon dioxide.
72
How is biodiesel obtained?
Refining oil and fats
73
How is biogas obtained?
From the breakdown of organic matter.
74
How is bioethanol obtained?
Sugar is fermented to produce ethanol.
75
What are the advantages of biofuels?
76
What are the disadvantages of biofuels?
77
What is a sigma bond?
The bond formed when two s orbitals overlap.
78
What is a pi bond?
Bond formed when two p orbitals overlap, forming an oblong shape.
79
Why do sigma bonds have a higher bond enthalpy than pi bonds?
Sigma bonds have more electron density (electrons are in a sphere between the two nuclei while in pi bonds it is just surrounding them).
Therefore electrostatic force of attraction is bigger in sigma bonds, so higher bond enthalpy.
80
Why are alkenes more reactive than alkanes?
They have a sigma and a pi bon, so high electron density. Electrons in the pi bond stick out a bit and the pi bond has a lower bond enthalpy.
This therefore makes it easier to the pi bond to be broken and so it is more reactive.
81
What are the products for the reaction between halogenoalkanes and water?
Alcohol and hydrogen halide.
82
What are the conditions needed for water to react with halogenoalkanes to produce an alcohol?
Heat the mixture as water reacts slowly with the halogenoalkane.
83
What type of reaction is the reaction between halogenoalkanes and water to give an alcohol and a hydrogen halide?
Nucleophilic substitution
84
Why do halogenoalkanes become more reactive as we go down the group?
Halide ion is bigger so there's less attraction between the nucleus and the bonding electrons (distance, shielding) therefore the bond is weaker and so the bond enthalpy is lower and therefore the bond is easier to break.
85
If we add If we react chlor, bromo and iodo alkanes with silver nitrate, in what order do the precipitates appear?
1. Yellow ppt (AgI)
2. Cream ppt (AgBr)
3. White ppt (AgCl)
86
What is the order in reactivity (from most reactive to least) for the primary, secondary and tertiary halogenoalkanes?
1. Tertiary
2. Secondary
3. Primary
87
What is a nucleophile?
An electron pair donor.
88
What are the products for the reaction between a halogenoalkane and a source of OH- ions (i.e. NaOH) with water as a solvent?
Alcohol + metal halide
89
What are the conditions for the reaction between OH- (aq) ions and a halogenoalkane?
Heat under reflux NaOH(aq)
| (or other OH- source)
90
What is the mechanism for the reaction between a halogenoalkane and OH- (aq)?
91
What are the products for the reaction between a halogenoalkane and potassium cyanide (or other cyanide ion source)?
Nitrile (+1 carbon in chain) and a salt i.e. potassium halide.
92
What are the conditions for the reaction between halogenoalkanes and potassium cyanide?
Heat ethanolic potassium cyanide under reflux.
93
What type of reaction is the reaction between halogenoalkanes and cyanide ions?
Nucleophilic substitution
94
What is the reaction mechanism for the reaction between a halogenoalkane and ethanolic potassium cyanide?
95
What are the products for the reaction between a halogenoalkane and ammonia?
Amine (fishy smell) and ammonium halide.
96
what are the conditions for the reaction between a halogenoalkane and ammonia?
Heat witn excess ethanolic ammonia
97
What is the mechanism for the reaction between a halogenoalkane and ethanolic excess ammonia?
98
What is are the products for the reaction between OH- ions dissolved in ethanol and a halogenoalkane?
Alkene + metal halide + water
99
What are the conditions for the reaction between a halogenoalkane and NaOH dissolved in ethanol?
Heat ethanolic sodium hydroxide under reflux.
100
What type of reaction is the reaction between a halogenoalkane and NaOH dissolved in ethanol?
Elimination
101
What is the mechanism for the reaction between a halogenoalkane and NaOH dissolved in ethanol?
102
During the reaction with a halogenoalkane, how do the hydroxide ions behave as when dissolved in water?
Nucleophile
103
During the reaction with a halogenoalkane, how do the hydroxide ions behave as when dissolved in ethanol?
Base (accepts an H+)
104
What is the equation for the reaction between an alcohol and phosphorous pentachloride to make a halogenoalkane?
105
What is the equation for the reaction between an alcohol and HCl to make a halogenoalkane?
106
When reacting to make halogenoalkanes, write, from slowest to fastest, at which speed do the different alcohols (primary, secondary...) react.
primary, secondary, tertiary.
107
What are the conditions to form a bromoalkane from an alcohol?
Add NaBr and acid catalyst (50% sulfuric acid)
108
How is a bromoalkane made from an alcohol?
NaBr reacts with sulfuric acid to create HBr.
Then:
R-OH + HBr \> R-Br + H2O
109
What type of reaction is the production of a halogenoalkane from an alcohol?
Nucleophilic subsitution.
110
What are the conditions to create an iodoalkane from an alcohol?
Heat under reflux alcohol, red phosphorus and iodine.
111
How is an iodialkane made from an alcohol?
The red phosphorous reacts with the idine in situ to make PI3.
Then:
112
What are the products for the dehydration of alcohols?
alkene + water
113
What are the conditions for the dehydration of alcohols?
Acid catalyst (sulfuric acid H2SO4 or phosphoric H3PO4)
114
In the dehydration of alcohols, where can the doublebond form in the resulting alkene?
Either side of the carbon bonded to the -OH.
115
What is the colour seen when potassium dichromate (K2Cr2O7) is reduced to Cr3+ during the oxidation of alcohols?
Orange to green
116
How do the different alcohols oxidise when heated under reflux with potassium dichromate?
1ary - aldehyde and further oxidises to carboxylic acid
2ary - ketone
3ary - isn't oxidised by potassium dichromate.
117
What is fehling solution?
Cu2+ dissolved in NaOH.
118
What is benedict's solution?
Cu2+ ions dissolved in sodium carbonate.
119
How can fehling and benedict's solution indicate if there's an aldehyde or a ketone?
Aldehyde - blue to brick red.
Ketone - No colour change. remains blue.
120
How can you use the technique of separation to purify an organic product?
- Add an aqueous layer to dissolve aqueous impurities.
- Remove the aqueous layer and keep the organic layer.
- Add anhydrous CaCl2 - it is a dehydrating agent and will remove the remaining aqueous solution.
- Filter the drying agent.
121
How do impurities affect boiling point?
Higher boiling point and substance boils over a bigger range.
