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AS Organic Flashcards

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1
Q

3 characteristics of a homogolous series

A

Same functional group
Same general formula
Consecutive members of a homogolous series differ by CH2 unit

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2
Q

What’s a sigma bond

A

Single covalent bond formed when 2 atomic orbitals on adjacent atoms overlap in a linear manner

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3
Q

What’s a pi bond

A

Covalent bond formed when 2 atomic p orbitals on adjacent atoms overlap in a sideway manner
(The horizontal one above a C=C bond)
They have high electron density - thus easily attacked by electrophiles

Every time you add a bond it’s pi bond

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4
Q

Define stereoisomerism

A

They have the same structural formula but different arrangement on space

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5
Q

When would E-Z isomers arise

A

When there’s restricted rotation in a C=C

When there are 2 different groups/atoms attached to both ends of the bond

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6
Q

What is optical isomerism

A

Occurs in carbon compounds in 4 different groups of atoms attached to a carbon aka asymmetric carbon/ CHIRAL CARBON

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7
Q

What does NOT superimposable mean

A

They are mirror images of each other

Molecules cannot be placed on top of one another and give the same spacial arrangement

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8
Q

What are enantiomers

A

Mirror images of each other

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9
Q

What is a racemic mixture

A

A mixture that contains an equimolar mix of the 2 isomers/enantiomers

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10
Q

How does optical isomers perform in plane polarised light

A

They rotate by the same amount in opposite directions

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11
Q

How does a racemic mixture perform in Plane polarised light

A

It doesn’t rotate

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12
Q

What does chirality mean

A

Mirror image / non superimposable

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13
Q

What is a petroleum fraction

A

Mixture of hydrocarbons with a similar chain length and boiling point range

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14
Q

How does petroleum fraction work

A

The fractions condense at different heights
The temperature of column decreases upwards
Separation depends on boiling points
Boiling point depends on size of molecules
The larger the molecule the larger VDW forces
Similar molecules condense together in which small molecules condense at the top at Lower temp

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15
Q

What is cracking

A

Conversion of large hydrocarbon to smaller hydrocarbon molecules by breakage of C-C bonds

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16
Q

Economic reasons for cracking

A
  • Petroleum fractions with shorter C chains are in more demand than larger fractions
  • Make use of excess larger hydrocarbons and to supply demand for shorter ones
  • Products of cracking are more valuable than the starting material
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17
Q

State the conditions of thermal cracking and what it produces

A

High pressure and high temperature

Produces mostly alkenes eg. Ethene used for making polymers

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18
Q

State the conditions of catalytic cracking

A

Low pressure
High temperature 500
Zeolite catalyst

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19
Q

What does catalytic cracking produce

What do these products do

A

Branched and cyclic alkanes -burns more cleanly

aromatic hydrocarbons

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20
Q

What is catalytic cracking used for, why is it better than thermal cracking

A

Used for making motor fuels

It is cheaper than thermal as lower temp and pressure is used

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21
Q

What can carbon cause

A

Global dimming

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22
Q

Name the 3 steps of FREE RADICAL SUBSTITUTION

A

Initiation
Propagation
Termination

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23
Q

State the condition needed for free radical substitution

A

UV light

Or heat to 300 degrees

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24
Q

What is a free radical

A

A reactive species which has an unpaired electron

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25
What is homolytic fission
Where each atom gets one electron from the covalent bond
26
Recall what happens in the 3 steps of free radical substitution
Initiation : The halogen eg, chlorine, undergo homolytic fission and forms free radicals Propagation : usually has 2 steps A chlorine free radical reacts with the Alkane to produce another free radical and a haloalkane Termination : 2 radicals join together to form the product
27
Why is SO2 harmful
It dissolves in atmospheric water to produce acid rain
28
How can SO2 be removed SO2 + _____ -> _____ What can the product then be used for
By passing through a scrubber containing basic calcium oxide, which reacts with the acidic SO2 in a neutralisation reaction. SO2 + CaO -> CaSO3 CaSO3 can be used to make CaSO4 for plasterboard
29
What facilitated the formation of nitrogen oxide in car engines and
The high temp and spark provides sufficient energy to break a strong nitrogen bonds
30
``` Pollutant : Environmental consequence NO. ? NO2. ? CO. ? CO2 C Unburnt hydrocarbon ```
NO is toxic - form acidic gas NO2 NO2 is toxic and acidic, forms acid rain CO - toxic CO2 - global warming C - global dimming and respiratory problems Unburnt hydrocarbon - contribute towards formation of smog
31
What are in catalytic converters that provides large surface area Name the catalysts
Ceramic honeycomb coated with a thin layer of catalyst metals like Platinum Rhodium Palladium
32
What are alkane fuels
Releasing energy when combusted
33
Why are alkanes not reactive
``` Lacks polarity (CH bond nonpolar) Strong covalent bonds ```
34
What’s a nucleophile
Electron pair donor | Donates their lone pair of electron to form a dative covalent bond
35
Out of chlorine iodine Florine and bromine, which one undergoes the fastest rate of substitution and why
Iodoalkanes are the fastest to substitute and fluoroalkanes are the slowest because C-I bond is the weakest thus the easiest to break
36
What is hydrolysis
It is the splitting of a molecule by a reaction with water
37
Out of Cl, I, Br, which one is the fastest to form precipitate with silver nitrate
Silver iodide forms the fastest. | It has the weakest bond and it is the most reactive
38
What is the mechanism, condition and reagent for the reaction of turning halogenoalkane to alcohol
Nucleophilic substitution KOH Heat under reflux in aqueous solution
39
Why is AQUEOUS condition so important in the nucleophilic substitution reaction of turning halogenoalkane to alcohol
Because if ethanol is used as solvent, elimination reaction occurs instead
40
Tertiary halogenoalkane undergo nucleophilic substitution (to turn alcohol) a different way, why and how
The halogen bond breaks first instead of having the nucleophile attack it. The nucleophile then starts attacking the intermediate. This is because tertiary carbocations is stabilised by the electron releasing methyl groups around it. Also the bulkiness prevent OH ion from attacking any other way.
41
What is the mechanism, reagent and condition for the reaction from haloalkane to nitrile
KCN dissolved in ethanol Nucleophilic substitution Heating under reflux
42
What do you add when you need to first increase carbon chain in organic synthesis
Add KCN so it turns into nitrile
43
Name the mechanism, reagent and condition for turning halogenoalkane to amine
NH3 dissolved in ethanol Heating under pressure Nucleophilic substitution
44
What is elimination
Removal of small molecule (often water) from the organic molecule
45
What is the role of OH- in an elimination reaction, how come?
It acts as a base because it attacks the Hydrogen instead of the carbon.
46
What is the mechanism when you go from halogenoalkane to Alkene? What is the reagent, condition
Elimination reaction KOH (with OH acting as base) Condition: heat in ethanol
47
What is a SN2 reaction
S stands for substitution, N for nucleophilic, and the 2 is because the initial stage of the reaction involves two species
48
What is a electrophile
An electron pair acceptor
49
Name the mechanism that turns alkene into halogenoalkane/dihalogenoalkane
Electrophilic addition
50
What is the typical condition of electrophilic addition reaction
Room temp
51
Why is a carbonation with 2 methyl group attached on the sides more stable
Methyl groups are electron releasing and reduces the charge on the ion which stabilises it
52
Know how H2SO4 structure is drawn
H-O-S=O | H-O- =O
53
What are the steps when H2SO4 is used in an elimination reaction to form alcohol from alkene? What is the role of H2SO4? How do you know 2 steps is needed in this, thus room temp is the only condition required
Stage1- electrophilic addition where you add H2SO4 onto it Stage2- hydrolysis by adding water then forming alcohol Sulphuric acid acts as a catalyst because it is regenerated
54
State the 3 essential conditions of hydration of alkenes to form alcohols CH2=CH2 + H2O -> CH3CH2OH
High temperature 300-600 High pressure 70atm Conc H3PO4 catalyst
55
Costs and Benefits of hydration of alkene to form alcohol
There are no waste products and so has a high atom economy High pressure means it can’t be done in the laboratory and has to be performed industrially
56
What reagent is used for oxidation reactions
Potassium dichromate solution and dilute sulphuric acid
57
What is the name of reaction, reagent and condition for primary alcohol to form aldehyde
Partial oxidation Dilute H2SO4 and K2Cr2O7 Limited amount of dichromate, warm gently and distill out the aldehyde as it forms
58
What is the observation when undergoing oxidation
Orange dichromate ion (Cr2o7^2-) reduces to green Cr3+ ion
59
What is the name,reagent and condition when a primary alcohol forms carboxylate acid
Full oxidation Dilute H2SO4 and K2Cr2O7 Heat under reflux and use excess dichromate
60
Name the reaction, reagent and condition when secondary alcohol forms ketone
Oxidation Dilute H2SO4 and K2Cr2O7 Heat under reflux
61
Name the reaction when alcohol -> alkene Name the reagents and their roles What’s the condition
Acid catalysed elimination Conc H2SO4/ phosphoric acid (acts as catalysts/dehydrating agent) They provides H+ Warm (under reflux)
62
What are the 2 methods of forming ethanol
Fermentation and industrial formation from ethene
63
Conditions needed for fermentation
Yeast No air Temp 30-40
64
Why is fermentation done in the absence of air
The presence of air can cause extra reactions to occur, it oxidised ethanol to produce ethanoic acid
65
Why is an optimum temp needed for fermentation
At lower temp, reaction is too slow | At higher temp, the yeast dies and enzyme denatures
66
What are the pros and cons of fermentation
``` Pro- Sugar is renewable resource -cheap Cons- Batch process which means it’s slow Ethanol is not pure which means it needs purifying by fractional distillation ```
67
Equation for fermentation
Glucose -> ethanol and Co2 | C6H12O6
68
If ethanol is formed from ethene, what reaction is this
Hydration/addition
69
Essential conditions for forming ethanol from ethene
Strong conc h3po4 High pressure 70atm High temperature 300
70
Pros and cons of producing ethanol from ethene
``` Pros- Faster Purer Continuous process Cons- Expensive Ethene is non renewable ```
71
What does the term carbon neutral means
No net carbon emissions to the atmosphere
72
How is ethanol produced from fermentation regarded as carbon neutral Use equations
As any co2 given off when biofuel is burnt would have been extracted from air by photosynthesis 6CO2 + 6H2O -> C6H12O6 + O2 C6H12O6 -> 2CH3CH2OH + 2CO2 2CH3CH2OH + O2 -> 4CO2 + 6H2O (when combusted)
73
What’s the reason fermentation may not be carbon neutral
If energy for this process comes from burning fossil fuels

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