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Chemistry > Introduction To Organic + Alkanes > Flashcards

Introduction To Organic + Alkanes Flashcards

1
Q

Skeletal formula

A

Shows bonds in carbon skeleton only

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2
Q

Homologous series (5)

A

Same functional group
Similar chemical properties
Trend in physical properties
Same general formula
Increase C chain length = +CH2 to formula

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3
Q

Aldehyde functional group and general formula

A

CHO
CnH2n+1OH

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4
Q

Ketone functional group and general formula

A

CO
CnH2nO

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5
Q

Carboxylic acid functional group and general formula

A

COOH
CnH2n-1COOH

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6
Q

Naming compounds priority list

A

Functional group
Alkenes
Alkyl group
Halogens

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7
Q

Name 2 types of isomerism and their subgroups

A

Structural
- positional
- functional group
- chain
Stereo
- geometric
- optical

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8
Q

Positional structural isomerism

A

Eg. 1 chloropropane and 2 chloropropane

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9
Q

Functional group structural isomerism

A

Eg. Propanone and propanal

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10
Q

Chain structural isomerism

A

Eg. Pentane and 2 - methyl butane
(Be careful no. Carbons, some are the same just inverted, not isomers)

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11
Q

Stereo isomer definition

A

Same molecular and structural formula but atoms are arranged in different areas of space

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12
Q

Describe cis/trans relationship

A

trans = same atoms on opposite carbons and opposite sides
cis = same atoms on opposite carbons but same sides

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13
Q

Why does E/Z cis/trans isomerism occur

A

C=C is planar
Alkenes
Pi bonds
Cant rotate

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14
Q

E/Z rules

A

All C attachments are different
Cis/trans = non-applicable
Greatest atomic number = highest priority
If same = go to next attached atom
2 highest priority = same side = Z
2 highest priority = different side = E

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15
Q

Name and describe 2 physical properties of alkanes

A

Low mp/bp
- weak LF only
- less ETO
- more length = higher mp/bp (more e density, stronger LF)
- unbranded = higher mp/bp (more SA, more contact points, more e density, stronger LF)
Water insoluble
- H bonds in water stronger than alkane LF
- Soluble in non polar liquids

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16
Q

Name and describe 2 chemical properties of alkanes

A

Relatively unreactive
- Non-polar bonds
- Strong C-C, C-H cov bonds
- dont react with acids, bases, ox/red agents
- react with halogens
Combust well

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17
Q

Name 6 step fractional distillation process

A

Crude oil heated in furnace
L/g mixture enters fractionating column
Ghost at bottom, cooler at top
HCs rise and condense at tray lower than bp
L piped off
Short HCs collect at top, lower mp/bp, weaker LFs

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18
Q

Fraction

A

Group of HCs with similar bps

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19
Q

Temperatures at top/bottom of fractionating column

A

350K
600K

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20
Q

8 fractions and uses

A

Refinery gases - camping stoves
Petrol - cars
Naphtha - rubber solvent
Kerosene - planes
Diesel - lorries
Lubricating oil - candles
Fuel oil - ships
Bitumin - tarmac roads

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21
Q

Describe fractions at the top of the fractionating column

A

Volatile
Flammable
Not viscous
Short HCs
Low bps

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22
Q

Describe fractions at the bottom of the fractionating column

A

Not volatile
Not flammable
Viscous
Long HCs
High bps

23
Q

Describe the cracking process

A

C-C bonds broken in LC HCs
Makes SC HCs (petrol/naphtha)
alkenes (polymers —> plastic)

24
Q

Why is cracking necessary

A

LC HC over abundant
Less useful, lower demand
Low supply for SC HCs
More useful, high demand
More reactive alkenes made
Monetise off waste products
Supply = demand, prices don’t rocket

25
Q

Name and describe 2 types of cracking

A

Thermal
- 1000C
- 70atm
Catalytic
- 450C (lower = cheaper)
- slight pressure
- zeolite catalyst (sulfur dioxide, aluminium oxide)
- catalyst increases ROR, decreases time and increases profit

26
Q

Reforming

A

Straight chain HCs —> branched/cyclo/aromatic alkanes
More efficient engine combustion
Catalyst, platinum, aluminium oxide

27
Q

Alkane combustion

A

Oxygen addition
Gases (l vaporised)
SC, more volatile, combust easier
Exothermic (more energy released forming new than absorbed breaking old)
LC, more bonds, more Kj/mol

28
Q

Name 6 pollutants

A

CO
CO2
Unburnt HCs
SO2
Nitrous oxides
Carbon

29
Q

CO

A

Poisonous
Binds to haemoglobin
Lower affinity than O2, not enough O2 —> organs
Can be fatal

30
Q

CO2

A

Greenhouse gas
Absorb IR rays
Cant reflect
Greenhouse effect —. Global warming

31
Q

Unburnt HCs

A

Greenhouse gas
Smog component
Irritates eyes/resp system (lung damage)

32
Q

Carbon

A

Global dimming
Carcinogen
Asthma

33
Q

SO2

A

HC sulfur impurities
React with O2 and water —> H2SO4 (acid rain)
Destroy vegetation, fish, buildings
(Remove using CaO/CaCO3)

34
Q

Nitrous oxides

A

Engines, high temp, N2 and O2 react
+ water —> HNO3 (acid rain)
Toxic, poisonous (asthma)

35
Q

Catalytic converters

A

Removes nitrous oxides, CO and Unburnt HCs
Platinum, rhodium
Honeycomb structure (high SA, high efficiency)
Products pass catalyst —> less harmful products
Make CO2 (gg but less harmful)

36
Q

Fossil fuels

A

Coal/oil/gas
Easily extracted
Produce lots of energy
Non renewable

37
Q

Biofuels pros and cons

A

Renewable
Make CO2
Car engines modified
Land fuel use, cant grow crop food
Deforestation

38
Q

3 types of biofuel

A

Bioethanol
- fermentation
Biodiesel
- refund fats
Biogas
- break organic waste

39
Q

What is a free radical

A

Particle with an unpaired electron
Very reactive

40
Q

Homolytic fission

A

Covalent bond splits
1 electron to each species using UV light

41
Q

3 stages of a chain reaction

A

Initiation
Propagation
Termination

42
Q

Describe the initiation stage of forming chloroalkanes

A

Break Cl-Cl bond —> 2X free radicals
UV light has more energy than bond (photodissociation)
Homolytic fission

43
Q

Describe the propagation stage of forming chloroalkanes

A

Chlorine free radical takes an H from methane
Makes hydrogen chloride and methyl free radical
Methyl radical reacts with chlorine molecule
Makes chloromethane and chlorine free radical
Chain reaction, repeated until CH4 or Cl2 used up
Cl free radicals regenerated, catalyst

44
Q

Describe the termination stage of forming chloroalkanes

A

Free radicals removed
2 free radicals react together
Stable compound, no free electrons formed
2 chlorine free radicals makes Cl2
2 methyl free radicals makes C2H6
Chlorine and methyl free radical make chloromethane

45
Q

Haloalkane synthesis conditions (3)

A
  • Dichloromethane can be made prop stage if chlorine radical reacts with chloromethane, excess cl, more substitution reactions
  • LC HCs = isomers form, excess methane, more branched alkyl groups
  • Not useful for specific products, unpredictable, made variety of products
46
Q

Describe the ozone layers (4)

A

O3
Stratosphere
Chemical sunscreen
Absorbs UV radiation from sun

47
Q

Why can UV radiation be harmful

A

Suburb, skin cancer

48
Q

Ozone layer equilibrium equations

A

O3 —> O2 + O*
O2 —> 2O*
O2 + O* —> O3 + heat

49
Q

Why is the ozone layers depleting

A

Human activity (CFCs and nitrous oxides)
More free radicals
Effect ozone natural balance

50
Q

Cl free radical formation from CFCs

A

CFCs decomposed by UV light
CFCl3 —> (UV) CFCl2 + Cl*
Cl* + O3 —> ClO* + O2
ClO* + O —> Cl* + O2
Less ozone

51
Q

Nitrous oxide free radical formation

A

NO —> (UV) NO*
NO* + O3 —> NO2* + O2
NO2* + O —> NO* + O2
Less ozone levels

52
Q

Benefits of CFCs

A

High volatility
Non toxic
Non flammable
No smell
Extremely un reactive

53
Q

Uses of CFCs

A

Refrigerants
Aerosols
Polystyrene blowing agents

Chemistry (24 decks)

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