Topic 6: Organic I Flashcards
General formula
Algebraic formula that can describe any member of a family of compounds
Empirical formula
Simplest whole ration number of atoms of each element in a compound
Molecular formula
Actual number of atoms of each element in a molecule
Structural formula
Shows the arrangement of atoms carbon by carbon, with attached hydrogens and functional groups
Skeletal formula
Shows bonds of the carbon skeleton only, with any functional groups
H atoms aren’t shown, C’s are vertices
Displayed formula
Shows how ll the atoms are arranged and ALL of the bonds between them
IUPAC nomenclature rules
- Find longest carbon chain to name alkane
- Identify functional groups and number Cs so that they are as small as possible
- Assign location of group using n° and place, then assemble in alphabetical order
Structural isomerism
Same molecular formula but different structural formula among atoms
chain, position or functional
They have different physical and chemical properties
Stereoisomers
Same molecular and structural formula but different spatial orientation of groups in the molecule
E-Z isomerism: restricted rotation about double bonds
Two different groups on each carbon of the C=C bond, highest atomic n° is the priority
Same side: Z (cis - if priority groups are equal)
Different side: E (trans)
Aldehydes
R-C=O-H
-anal
Ketones
R2-C=O-R1
R2+R1 = starting molecule
-anone
E.g ethanone
Alkanes
CnH2n+2
Saturated hydrocarbons, only single covalent bonds
Main constituents of crude oil, used as fuel
Need to be reformed as straight chain alkanes cause knocking (small explosions in engine, combustion less efficient)
Platinum catalyst to reform into branched and cyclic alkanes
Fractionating Column
Petroleum enters vaporised at bottom left
Boiling point decreases as you go up (so each product condenses at a different temp)
Length of carbon chain decreases upwards (volatility is inversely proportional to carbon chain length)
Products: (upwards)
Bitumen, fuel, diesel, kerosene, naphtha, gasoline, refinery gas
Thermal Cracking
Decomposition reaction, breaking C-C bonds in long alkanes
Homolytic Fission: free radical reaction
High temp: 450-900°C
High pressure: up to 7000 kPa
Catalytic Cracking
High temp: 450°C, pressure slightly above atmospheric pressure (around 100kPa)
Zeolite catalyst (large surface area)
Produces more branched, cyclic and aromatic HCs (more useful for making fuels) so more productive than thermal
Free Radical Substitution
Photochemical reaction: UV light provides activation energy
Alkane -> haloalkane + HX
1. Initiation: homolytic fission produces two radicals
2. Propagation: spread of radicals, chain reaction
3. Termination: radicals react together
RADICALS: species with an unpaired electron, highly reactive
Pollutants: Carbon Monoxide
incomplete combustion of fuels (road transport)
reacts with haemoglobin & reduces oxygen-carrying capacity of blood
reacts with other gases to form ozone
Pollutants: Carbon Dioxide
burning fossil fuels to produce electricity, natural processes e.g respiration
anthropogenic global warming
Pollutants: Oxides of Nitrogen
Combustion in road transport
NO -> global warming contributor
NO2 -> ground level ozone forming & component of smog**
SMOG: permanent fog of pollution
Pollutant: Sulfur dioxide (SO2)
burning fossil fuels to generate electricity
Smog, produces acid rain and causes breathing problems
Catalytic Converters
CO + 2NO -> CO2 + N2
Catalyst: platinum/palladium on honeycomb
1. ADsorption: reactants weakly bond to catalyst surface
2. Reaction: bonds in reactants weakened (shaking), lower Ea needed for chemical reaction
3. DEsorption: products released from catalytic surface
Alternative Fuels
to reduce pollution from combustion & due to limited amount of non-renewable
BIODIESEL: refining renewable fats & oils
BIOETHANOL: fermentation
BIOGAS: released when organic waste breaks down
Benefits: carbon neutral, reduce waste in landfills, production gives money to less developed countries where crops are grown
Drawbacks: cost of changing engines, developed countries don’t have enough space for crops
Alkenes
CnH2n, unsaturated hydrocarbons, C=C
Decolourise Br water
have stereoisomerism and are functional group isomers to cycloalkanes
Bonding in Alkenes
single covalent bonds are sigma, orbitals overlap end-to-end
double covalent bonds have one sigma and one pi bond, sideways bonding of p orbitals with s orbital in the middle
Addition reactions of Alkenes
- Alkenes + halogens -> dihaloalkane
- Alkenes + steam -> alcohol
- Alkenes + hydrogen -> alkane (hydrogenation)
Electrophilic addition
Electrophile: a species attracted to a negative region
