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Flashcards in AS Organic Deck (73):
1

3 characteristics of a homogolous series

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

2

What’s a sigma bond


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

3

What’s a pi bond

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

4

Define stereoisomerism

They have the same structural formula but different arrangement on space

5

When would E-Z isomers arise

When there’s restricted rotation in a C=C
When there are 2 different groups/atoms attached to both ends of the bond

6

What is optical isomerism

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

7

What does NOT superimposable mean

They are mirror images of each other

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

8

What are enantiomers

Mirror images of each other

9

What is a racemic mixture

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

10

How does optical isomers perform in plane polarised light

They rotate by the same amount in opposite directions

11

How does a racemic mixture perform in Plane polarised light

It doesn’t rotate

12

What does chirality mean

Mirror image / non superimposable

13

What is a petroleum fraction

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

14

How does petroleum fraction work

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

15

What is cracking

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

16

Economic reasons for cracking

-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

17

State the conditions of thermal cracking and what it produces

High pressure and high temperature

Produces mostly alkenes eg. Ethene used for making polymers

18

State the conditions of catalytic cracking

Low pressure
High temperature 500
Zeolite catalyst

19

What does catalytic cracking produce

What do these products do

Branched and cyclic alkanes -burns more cleanly
aromatic hydrocarbons

20

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

Used for making motor fuels

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

21

What can carbon cause

Global dimming

22

Name the 3 steps of FREE RADICAL SUBSTITUTION

Initiation
Propagation
Termination

23

State the condition needed for free radical substitution

UV light
Or heat to 300 degrees

24

What is a free radical

A reactive species which has an unpaired electron

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