Introduction To Organic + Alkanes Flashcards
Skeletal formula
Shows bonds in carbon skeleton only
Homologous series (5)
Same functional group
Similar chemical properties
Trend in physical properties
Same general formula
Increase C chain length = +CH2 to formula
Aldehyde functional group and general formula
CHO
CnH2n+1OH
Ketone functional group and general formula
CO
CnH2nO
Carboxylic acid functional group and general formula
COOH
CnH2n-1COOH
Naming compounds priority list
Functional group
Alkenes
Alkyl group
Halogens
Name 2 types of isomerism and their subgroups
Structural
- positional
- functional group
- chain
Stereo
- geometric
- optical
Positional structural isomerism
Eg. 1 chloropropane and 2 chloropropane
Functional group structural isomerism
Eg. Propanone and propanal
Chain structural isomerism
Eg. Pentane and 2 - methyl butane
(Be careful no. Carbons, some are the same just inverted, not isomers)
Stereo isomer definition
Same molecular and structural formula but atoms are arranged in different areas of space
Describe cis/trans relationship
trans = same atoms on opposite carbons and opposite sides
cis = same atoms on opposite carbons but same sides
Why does E/Z cis/trans isomerism occur
C=C is planar
Alkenes
Pi bonds
Cant rotate
E/Z rules
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
Name and describe 2 physical properties of alkanes
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
Name and describe 2 chemical properties of alkanes
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
Name 6 step fractional distillation process
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
Fraction
Group of HCs with similar bps
Temperatures at top/bottom of fractionating column
350K
600K
8 fractions and uses
Refinery gases - camping stoves
Petrol - cars
Naphtha - rubber solvent
Kerosene - planes
Diesel - lorries
Lubricating oil - candles
Fuel oil - ships
Bitumin - tarmac roads
Describe fractions at the top of the fractionating column
Volatile
Flammable
Not viscous
Short HCs
Low bps
Describe fractions at the bottom of the fractionating column
Not volatile
Not flammable
Viscous
Long HCs
High bps
Describe the cracking process
C-C bonds broken in LC HCs
Makes SC HCs (petrol/naphtha)
alkenes (polymers —> plastic)
Why is cracking necessary
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
Name and describe 2 types of cracking
Thermal
- 1000C
- 70atm
Catalytic
- 450C (lower = cheaper)
- slight pressure
- zeolite catalyst (sulfur dioxide, aluminium oxide)
- catalyst increases ROR, decreases time and increases profit
Reforming
Straight chain HCs —> branched/cyclo/aromatic alkanes
More efficient engine combustion
Catalyst, platinum, aluminium oxide
Alkane combustion
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
Name 6 pollutants
CO
CO2
Unburnt HCs
SO2
Nitrous oxides
Carbon
CO
Poisonous
Binds to haemoglobin
Lower affinity than O2, not enough O2 —> organs
Can be fatal
CO2
Greenhouse gas
Absorb IR rays
Cant reflect
Greenhouse effect —. Global warming
Unburnt HCs
Greenhouse gas
Smog component
Irritates eyes/resp system (lung damage)
Carbon
Global dimming
Carcinogen
Asthma
SO2
HC sulfur impurities
React with O2 and water —> H2SO4 (acid rain)
Destroy vegetation, fish, buildings
(Remove using CaO/CaCO3)
Nitrous oxides
Engines, high temp, N2 and O2 react
+ water —> HNO3 (acid rain)
Toxic, poisonous (asthma)
Catalytic converters
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)
Fossil fuels
Coal/oil/gas
Easily extracted
Produce lots of energy
Non renewable
Biofuels pros and cons
Renewable
Make CO2
Car engines modified
Land fuel use, cant grow crop food
Deforestation
3 types of biofuel
Bioethanol
- fermentation
Biodiesel
- refund fats
Biogas
- break organic waste
What is a free radical
Particle with an unpaired electron
Very reactive
Homolytic fission
Covalent bond splits
1 electron to each species using UV light
3 stages of a chain reaction
Initiation
Propagation
Termination
Describe the initiation stage of forming chloroalkanes
Break Cl-Cl bond —> 2X free radicals
UV light has more energy than bond (photodissociation)
Homolytic fission
Describe the propagation stage of forming chloroalkanes
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
Describe the termination stage of forming chloroalkanes
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
Haloalkane synthesis conditions (3)
- 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
Describe the ozone layers (4)
O3
Stratosphere
Chemical sunscreen
Absorbs UV radiation from sun
Why can UV radiation be harmful
Suburb, skin cancer
Ozone layer equilibrium equations
O3 —> O2 + O*
O2 —> 2O*
O2 + O* —> O3 + heat
Why is the ozone layers depleting
Human activity (CFCs and nitrous oxides)
More free radicals
Effect ozone natural balance
Cl free radical formation from CFCs
CFCs decomposed by UV light
CFCl3 —> (UV) CFCl2 + Cl*
Cl* + O3 —> ClO* + O2
ClO* + O —> Cl* + O2
Less ozone
Nitrous oxide free radical formation
NO —> (UV) NO*
NO* + O3 —> NO2* + O2
NO2* + O —> NO* + O2
Less ozone levels
Benefits of CFCs
High volatility
Non toxic
Non flammable
No smell
Extremely un reactive
Uses of CFCs
Refrigerants
Aerosols
Polystyrene blowing agents
