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Terms in this set (40)
Compounds with the same molecular formula but different structural formulae
When a covalent bond breaks and each bonding atom receives one electron from the bonded pair
Species with an unpaired electron
When a covalent bond breaks and one bonded atom receives both electrons from the bonded pair
What is an alkane?
A saturated hydrocarbon, with C—C and C—H bonds only
What is a use of an alkane?
What sort of bonds occur between alkanes?
What is a sigma bond?
Single bond, where two orbitals overlap (linear overlap of orbitals)
What happens to the boiling point of alkanes as chain length increases?
It increases because the molecule has more electrons and so the strength of the London forces increases, so more energy is needed to overcome the forces of attraction
How does branching affect the boiling point of alkanes?
Unbranched alkanes have more surface points of contact (as they can get closer together), so the London forces are stronger, and the boiling point increases
What is the reactivity of alkanes?
Why do alkanes have low reactivity?
The C—C and C—H sigma bonds are strong; the C—C bonds are non-polar; the electronegativity of C and H is similar, so the bonds are considered non-polar, and so can't attract positive or negative chemicals
What happens when hydrocarbons combust in oxygen?
They release heat energy (exothermic)
What is complete combustion?
When something is burnt with a sufficient oxygen supply
What are the products of complete combustion?
Carbon dioxide and water
What is incomplete combustion?
When something is burnt with an insufficient oxygen supply
What are the products of incomplete combustion?
Carbon, carbon monoxide carbon dioxide and water
What are the problems with carbon monoxide?
It's poisonous, odourless and colourless, so can't be detected; it bonds to haemoglobin; it forms in internal combustion engines; in homes the oxygen supply to appliances becomes (partially) blocked
How is a haloalkane formed?
What is substitution?
When one atom or group is replaced by another atom or group
What steps are included in radical substitution?
Initiation, propagation and termination
What happens in initiation?
Energy from UV light makes the covalent bond break by homolytic fission
What happens in propagation?
There are two steps. The chain reaction continues until all radicals have undergone the termination step
What happens in termination?
A molecule is formed when two radicals combine, and the number of radicals present determines the number of products
What are the limitations of radical substitution?
It is difficult to produce a pure product which limits its use in chemical synthesis
Further substitution reactions
Substitution at different places on the C chain
What is an alkene?
An unsaturated hydrocarbon containing a C double bond C
What bonds are in a double bond?
A sigma bond and pi bond
What is a pi bond?
A sideways overlap of adjacent p-orbitals above and below the bonding C atoms
What shape does a pi bond have?
What is a stereoisomer?
Compounds with the same structural formula but with a different arrangement of atoms in space
What is E/Z isomerism?
Different groups are attached to each C of a C double bond C, may be arranged differently in space due to the restricted rotation of the C double bond C
What is cis-trans isomerism?
A special type of E/Z isomerism where two of the substituent groups attached to each C atom in the C double bond C are the same
What is the Cahn-Ingold-Prelog priority rule?
The higher the atomic number, the higher the priority
Why can alkenes react?
A C double bond C has a pi bond, which has a lower bond enthalpy
What is an addition reaction?
When two atoms or groups are added across a double bond
What are the conditions for hydrogenation?
T- 150 degrees
How can you test for the presence of an alkene?
Add bromine water, goes from orange to colourless
What is the reaction between alkenes and steam?
T: 300 degrees
P: 60 atm
What is an electrophile?
An atom or group of atoms attracted to an electron rich centre or atom, where it accepts a pair of electrons to form a new covalent bond
How do bonds break in electrophilic addition?
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