Organic chemistry Flashcards
What are the chemical properties of Carbon?
Carbon can form rings and very long chains, which may be branched
Carbon atom has four electrons in its outer shell, so it forms four covalent bonds
The carbon-hydrogen bond is also strong (413 kJ mo1-1)
Relatively non-polar. Hydrocarbon chains form the skeleton of most organic compounds
What does molecular formula show?
Shows the actual number of atoms of each element in the molecule
How are free radicals formed?
When a covalent bond (which consists of a pair of electrons shared between two atoms) may break in such a way that one electron goes to each atom that originally formed the bond. These fragments of the original molecule - then have free radicals
What are the types of functional groups? What are the prefixes?
Alkanes (-ane)
Alkenes (-ene)
Halogenalkanes
Alcohols (-ol)
Aldehydes (-al)
Ketones (-one)
Carboxylic Acid (-ioc acid)
What is a functional group?
A reactive group
What is the function of the IUPAC?
This is an international organisation of chemists that draws up standards so char chemists throughout the world use the same conventions- like a universal language of chemistry
What does the systematic name tell us?
Systemaric names tell us abour the structures of the compounds
What does IUPAC stand for?
International Union of Pure and Applied Chemistry
What is the root name for (each numb. of carbon)?
1 Carbon - Meth
2 Carbon - Eth
3 Carbon - Prop
4 Carbon - But
5 Carbon - Pent
6 Carbon - Hex
What is a homologous series?
is a family or organic compounds with the same functional group, but different carbon chain length.
What are isomers?
are molecules that have the same molecular formula but whose atoms are arranged differently
What are the types of isomerism?
structural isomerism
stereo-isomeris
What are structural isomers?
having the same molecular formula but different structural formulae
What are the three types of structural isomers? What are they like?
Positional Isomers - the same functional groups attached to the main chain at different points.
Functional group isomerism -functional groups that are different
Chain isomerism - a different arrangement of the hydrocarbon chain.
What are stereoisomerism?
is where two (or more) compounds have the same structural formula. They differ in the arrangement of the bonds in space
What are the types of stereoisomerism?
E-Z isomerism
Optical Isomerism
What does E-Z isomerism tell you?
E-Z isomerism tells us about the positions of substituents at either side of a carbon-carbon double bond.
Same side of the bond - Z (cis)
Opposite side - E (trans)
What can’t you convert E - isomers to Z - isomers or vice versa?
This is because substituted groups joined by a single bond can rotate around the single bond, so there are no isomers. But there is no rotation around a double bond
What are the physical properties of an alkane?
[Polarity]
Have weak inter-molecular forces between their molecules and are van der walls ( The larger the molecule the larger the van der walls)
They are non-polar because of their electronegativies are similar
[Boiling Point]
Boiling points of alkanes increase as the chain length increases
Short chains tend to be gases at room temperature but at chain length they tend to be solid
Alkanes with branched chains have lower melting points than straight chain alkanes with the same number of carbon atoms - because they cannot pack together as closely as unbranched chains and so the van der Waals forces are not so effective
[Solubility]
Alkanes are insoluble in water - This is because water molecules are held together by hydrogen bonds which are much stronger than the van der Waal’s forces that act between alkane molecules
How reactive is alkanes?
They are relatively unreactive
They do not react with with acids, bases, oxidising agents or reducing agents
They burn and react with halogens when in plenty of oxygen
How is fractional distillation of crude oil done?
The crude oil is first heated in a furnace
A mixture of liquid and vapour passes into a tower that is cooler at the top than at the bottom
The vapours pass up the tower via a series of trays containing bubble caps until they arrive at a tray that is sulficiently cool (at a lower temperature than their boiling point). Then they condense to liquid
The mixture of liquids that condenses on each tray is piped off.
The shorter chain hydrocarbons condense in the trays nearer to the top of the tower, where it is cooler, because they have lower boiling points
The thick residue that collects at the base of the tower is called tar or bitumen. This fraction is often further processed to give more valuable products
How was crude oil formed?
it was formed Millions of years ago by the breakdown of plant and animal remains at the high pressures and temperatures deep below the Earth’s surface
What causes sulfer dioxide when crude oil is burnt?
small amounts of other compounds dissolved in it.These come from other elements in the original plants and animals the oil was formed from (e.g. sulfer)
What causes the formation of acid rain?
Sulphur dioxide reacts with oxygen high in the atmosphere to form Sulfur trioxide. This reacts with water in the atmosphere to form sulfuric acid.
How is thermal cracking carried out?
First heating alkanes to a high temperature,
700-1200K under high pressure, up to 7000 kPa
The carbon-carbon bonds break in such a way that one electron from the pair in the covalent bond goes to each carbon atom
Initially two shorter chains are produced, each ending in a carbon atom with an unpaired electron. These fragments are called free radicals.
Free radicals are highly reactive intermediates and react in a number of ways to form a variety of shorter chain molecules.
As there are not enough hydrogen atoms to produce two alkanes, one
of the new chains must have a C= C
What products are commonly formed by a result of Catalytic Cracking?
Products tend to be:
> Alkanes
> Cycloalkanes
> Aromatic Compounds
Commonly used to produce motor fuels
What is the physical structure of zeolites and what are there chemical properties?
They consist of silicon dioxside and aluminium oxide
They have a honeycomb structure with enormous surface area
They are acidic
Give examples of alkane fuels and there uses?
Methane
Propane - used as camping gas
Butane - Calor gas
Petrol and paraffin
What are the components of a chain reaction? When does this happen?
1) Initiation
2) Propagation
3) Termination
reaction between an alkane and halogen
Why are chlorine bad for ozone?
They act as a catalyst in the breakdown of ozone to oxygen
How does CFCs contribute the the breakdown of the ozone layer?
Chlorine free radicals are formed from CFCs because the C-Cl bond breaks homolytically in the presence of UV radiation to produce chlorine free radicals.
Ozone molecules are then attacked by
these:
Cl• + 03—>• CIO• + 02
The resulting free radicals also attack ozone and regenerate Cl•:
CIO• + 0(3) —> 20(2) + Cl•
Why is ozone important?
> Protects the Earth from the harmful exposure to too many ultraviolet (UV) rays
> Too much UV radiation causes skin cancer in people by damaging DNA
What is ozone?
a molecule made from three oxygen atoms, O(3)